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    Structural Composition and Stability of Oil Bodies from 5 Tree Nuts
    SUN XiaoYan, JIN Feng, YANG XuChang, WANG FengJun, ZHOU Ye
    Scientia Agricultura Sinica    2024, 57 (10): 2023-2034.   DOI: 10.3864/j.issn.0578-1752.2024.10.013
    Abstract11)   HTML1)    PDF (8120KB)(5)       Save

    【Objective】 In oilseeds, lipids are mainly stored in the organelles called oil bodies. Tree nuts, such as walnut and hazelnut, were important oilseed crops. Among the 5 selected tree nuts, the differences in morphology, structure and stability of their oil bodies were evaluated and discussed, which could provide the new ideas for the utilization of the nut oils.【Method】 5 tree nuts were used as materials, including walnut, almond, hazelnut, pecan, and pine nut. The morphology and size of the oil bodies inside the cells of different nut seeds were observed and compared by employing transmission electron microscope. The oil body membrane proteins were separated by SDS-PAGE, followed by the LC-MS/MS identification of the protein bands. The oil body membrane phospholipids, as well as the intrinsic triacylglycerols, were also analyzed through lipidomics. The stability of oil bodies was evaluated by analyzing their changes in morphology peroxide values and thiobarbituric acid values during storage under room temperature.【Result】 The cells of the nut seeds were occupied by the oil bodies and proteosomes. The asymmetric spheroid-shaped oil bodies were covered by intact membranes. The pecan oil body had the largest average diameter (2.34±0.48) μm, while the almond oil body had the minimum (1.21±0.19) μm. For all nut samples, oleosin was the most important oil body membrane protein, accounting for 72.76%-84.15% of the total amount of membrane proteins. Oleosin had a narrow molecular weight distribution of 14.7-18.8 kDa, yet the numbers of oleosin isomers were quite different. Caleosin accounted for 14.34%-4.96% of the total amount of membrane proteins, and its molecular weight in different nuts was approximately 26.5-27.1 kDa. No caleosin isomer was found in each nut sample. Steroleosin, accounted for 8.95%-12.89% of the total amount of membrane proteins, was identified only in walnut, pecan and pine nut oil bodies. The oil bodies of the 5 tree nuts had different triacylglycerol compositions but similar membrane phospholipid compositions. Phospholipidine (PS) and phosphatidylcholine (PC) were the most important oil body membrane phospholipids, accounting for 67.91%-75.06% of the total amount of membrane phospholipids. The proportion of unsaturated fatty acyl chains in membrane phospholipids was 69.64%-74.52%, while 38.64%-45.15% of the fatty acyl groups were oleoyls. The hazelnut oil body showed the highest stability at room temperature. During storage, the oil bodies aggregated and fused gradually, accompanied by an increasing degree of lipid oxidation. Eventually the phase separation phenomenon in oil body emulsions was observed.【Conclusion】 Among the oil bodies from 5 tree nuts, the pecan oil body was the largest in size, while the hazelnut oil body was the most stable. The different tree nut oil bodies had similar constituents of membrane proteins and membrane phospholipids, but there were significant differences in the number of oleosin isomers, triacylglycerol compositions and constituent proportions. The ratio of lipid content to oleosin, as well as the ratio of oil body membrane phospholipids to oil body membrane proteins, might have important influences on the size and stability of the oil bodies.

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    The Stabilization of Aroma and Color During Hutai-8 Rose Winemaking by Gallic Acid Treatment
    FENG Fan, JIANG XingRui, WANG LingYun, ZHANG YongGang, LI AiHua, TAO YongSheng
    Scientia Agricultura Sinica    2024, 57 (8): 1592-1605.   DOI: 10.3864/j.issn.0578-1752.2024.08.013
    Abstract50)   HTML10)    PDF (1713KB)(35)       Save

    【Objective】This study was aimed to investigate the effects of gallic acid treatment on color and aroma preservation during the aging process of Hutai-8 rosé wine, in order to optimize the design of color and aroma enhancement techniques for rosé wine production. 【Method】In this study, Hutai-8 grape was used as raw material. Gallic acid was added at three different stages, including pre-fermentation (Pr), mid-fermentation (M), and post-fermentation (Po), with the concentrations of 200 and 300 mg∙L-1. After a 6-month storage period following fermentation, the aroma compounds of the wine samples were analyzed by headspace solid-phase microextraction-Gaschromatography-mass spectrometry (HS-SPME-GC-MS). The color parameters (L*, a*, b*, C*ab, Hab, and Δ*Eab) were determined by the CIELab color space parameters, and the color indices were measured by ultraviolet spectrophotometer (UV). Finally, the sensory evaluation was conducted to analyze the influences of different treatments on the aroma characteristics of the wine samples. 【Result】The post-fermentation treatments significantly increased the content of fermentation aroma compounds compared with CK, with an increase of approximately 16%. However, there was little difference between treatments of the two additive concentrations. The pre-fermentation treatments positively contributed to the preservation of varietal aroma compounds, with an increase of approximately 65%-73% compared with CK. The mid-fermentation treatments had a lesser stabilizing effect on the aroma compounds of the wine. Sensory evaluation results showed that post-fermentation treatment had the best effect on improving the overall aroma of the wine, and the pre-fermentation treatment was more effective than the mid-fermentation treatment. PLSR models revealed that terpenols, fatty acids, higher alcohols, acetates and fatty acid ethyl esters were the main aroma contributors (regression coefficients>0.1) to floral and citrus attributes (R2c>0.80 & R2v>0.70), with fatty acid ethyl esters and acetates being particularly prominent contributors. The color analysis results showed that pre-fermentation had a significant color-preserving effect, and the treatment with 200 mg∙L-1 (Pr1) was more effective than the treatment with 300 mg∙L-1 (Pr2). Comparied with CK, Pr1 treatment group’s, L* value decreased by 0.58% and a* value increased by 45.38%. Furthermore, the color characterization results showed that pre-fermentation treatment enhanced the purple-red tone of Hutai-8 rosé wine and the treatment with 200 mg∙L-1 was more effective than the treatment with 300 mg∙L-1. 【Conclusion】The addition of 200 mg∙L-1 gallic acid before fermentation had a significant effect on stabilizing the color of Hutai-8 rose wine, while the post-fermentation treatments could significantly increase the fermentative aroma content of wine.

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    Analysis of the Effect of Dielectric Barrier Discharge Cold Plasma on Phenolic Metabolism of Stored Paddy Rice Under High Temperature Stress
    HOU Shuai, ZHANG YiJia, ZHOU DanDan, MA FeiYang, WANG DaPeng, ZHAO SiQi, DING Chao, LIU Qiang
    Scientia Agricultura Sinica    2024, 57 (6): 1180-1190.   DOI: 10.3864/j.issn.0578-1752.2024.06.012
    Abstract78)   HTML4)    PDF (948KB)(67)       Save

    【Objective】 The aim of his study was to explore the impact of dielectric barrier discharge cold plasma (DBD-CP) treatment on the phenolic metabolism of stored rice under high-temperature stress.【Method】 Under simulated summer high- temperature conditions (35 ℃), fresh high-moisture rice (Japonica rice, 16.0% moisture content on a wet basis) was used as the raw material, the effects of DBD-CP treatment on quality parameters such as L*, a*, b*, yellowness index (YI), reactive oxygen species, and malondialdehyde (MDA) in stored rice were analyzed. Additionally, the study aims to analyze the changes in total phenols, total flavonoids, and antioxidant activities during the storage process. The investigation would involve multiple validations, including ABTS+ and DPPH radical scavenging activities, ferric ion reducing power, and the activity changes of key rate-limiting enzymes in phenylpropane metabolism. The ultimate goal was to explore the impact of DBD-CP treatment on the phenolic metabolism of stored rice. 【Result】 After DBD-CP treatment, the color stability of rice during storage significantly improved. The yellowing index of the treatment group decreased significantly by 12.6% after 60 days of storage. After 20 days of storage, the levels of superoxide anion, hydrogen peroxide, and MDA decreased by 14.8%, 41.6%, and 21.6%, respectively, and the deterioration rate of fresh high-moisture rice was significantly inhibited. Additionally, during the high-temperature stress storage period, the total phenol and total flavonoid content in the treatment group increased simultaneously (P<0.05), with maximum increases of 1.23 and 1.34 times, respectively. The antioxidant properties and iron ion reduction capacity of the corresponding samples were also improved (P<0.05). Combined with the analysis of the activity of key limiting enzymes in phenylpropane metabolism, the activities of phenylalanine ammonia-lyase (PAL), cinnamic acid-4-hydroxylase (C4H), and chalcone synthase (CHS) were significantly enhanced, with increases ranging from 1.71 to 2.28 times. Further correlation analysis confirmed the close association (P<0.05) between the content of phenolic substances in high-moisture rice under high-temperature stress and the activities of PAL, C4H, and CHS enzymes, and a significant negative correlation (P<0.05) with internal reactive oxygen species and MDA content. 【Conclusion】 Dielectric barrier discharge cold plasma treatment could promote the synthesis rate of phenolic compounds within the grains of high-moisture rice by activating phenylpropane metabolism. This treatment enhanced the tissue's antioxidant properties, alleviated membrane lipid peroxidation, and reduced the accumulation of free radicals. As a result, it delayed the quality deterioration of rice under high-temperature storage conditions.

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    Effects of Novel Phase Change Coolant on the Postharvest Quality of Shiitake Mushrooms
    HUANG Hao, WU QingHong, ZHANG Yu, WANG Ye, LIU QingE, FANG YiDa, LUO ZiSheng
    Scientia Agricultura Sinica    2024, 57 (5): 989-999.   DOI: 10.3864/j.issn.0578-1752.2024.05.013
    Abstract67)   HTML7)    PDF (847KB)(58)       Save

    【Background】Edible mushrooms with unique flavor are rich in protein, vitamins, and a variety of bioactive components, such as polysaccharides, phytosterol, etc. China is the major country in the cultivation and consumption of edible mushrooms, among which shiitake mushroom (Lentinula edodes) is the most widely cultivated. The current coolants exhibit low phase change temperature, which may result in chilling injury of shiitake mushrooms.【Objective】 Based on the freezing temperature of shiitake mushrooms, a novel phase change coolant specially for shiitake mushrooms was developed to maintain the postharvest quality.【Method】The main component of the coolant was screened by differential scanning calorimetry (DSC) based on the phase change latent heat and phase change temperature. Potassium sulfate, nano titanium dioxide, and superabsorbent resin were mixed to prepare the coolant. The effects of coolant on the qualities of shiitake mushrooms were studied by the weight loss rate, color, hardness and other indexes. The activities of enzymes related to glutamate metabolism and energy metabolism were also measured to explore the mechanism of preservation.【Result】 The aqueous solution of maltitol was selected as the main component by DSC. The optimal compositions of coolant were 1.85% of maltitol, 2.35% of potassium sulfate, 0.02% of nano titanium dioxide, and 0.80% of super absorbent resin, leading to the phase change latent heat and temperature at 405.26 J·g-1 and -1.8 ℃, respectively. Compared with the control group, under the low-temperature conditions provided by the refrigerant, the weight loss rate of shiitake mushrooms decreased by 51.92%, and the hardness and brightness increased by 66.67% and 41.94%, respectively. The shelf life of shiitake mushrooms was extended. The low temperature also regulated the activities of enzymes, which were related to glutamate metabolism and energy metabolism, the glutamic acid and energy charge level increased by 36.64% and 54.76%, respectively. Finally the freshness of shiitake mushroom was maintained.【Conclusion】The novel phase change coolant based on the freezing temperature of shiitake mushrooms could maintain the weight, color, hardness and other indexes, regulate the level of glutamic acid and energy, and delay the deterioration of shiitake mushrooms. Therefore, the coolant was effective for the cold-chain preservation of shiitake mushrooms.

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    Effect of Pleurotus eryngii Powder on Quality Characteristics of Extruded Rice
    JIANG Wen, LIANG WenXin, PEI Fei, SU AnXiang, MA GaoXing, FANG Donglu, HU QiuHui, MA Ning
    Scientia Agricultura Sinica    2024, 57 (4): 779-796.   DOI: 10.3864/j.issn.0578-1752.2024.04.012
    Abstract81)   HTML13)    PDF (2239KB)(68)       Save

    【Objective】The twin-screw extrusion process was used to produce extruded rice products with P. eryngii powder and rice flour as raw materials, and the predicted glycemic index of the products was analyzed to provide technical support for the development of edible mushroom extruded rice products with comprehensive nutrition and low glycemic index. 【Method】 The content of protein, crude fiber, amino acid and fat of extruded rice with 20%, 40% and 60% P. eryngii powder were determined. RVA rapid viscosity analyzer and rotary rheometer were used to analyze the gelatinization properties and rheological properties of P. eryngii powder with different additive amounts. The internal structure, color, texture properties, starch hydrolysis rate, predicted glycemic index (pGI) and sensory score of extrusion-rice with different dosage of P. eryngii were analyzed by scanning electron microscopy, colorimeter, texture analyzer, and in vitro digestion and sensory evaluation. 【Result】Compared with blank extruded rice, the content of protein, crude fiber and amino acid in extruded rice was significantly increased by adding P. eryngii powder, and the content of protein was increased by 71.84%, 70.19% and 96.70%, and the content of crude fiber was increased by 850%, 2350% and 3750%, respectively. The total amino acid content increased by 40.98%, 58.96% and 66.03%, respectively. The gelatinization and rheological properties of the mixed powder system showed a decreasing trend with the increase of the added amount of P. eryngii powder, and the peak viscosity, valley viscosity, final viscosity, disintegration value and recovery value gradually decreased, and G' and G" gradually decreased. The typical weak gel accounted for a large proportion of elasticity, and the added amount of 20% P. eryngii powder was the closest to the powder parameters of rice flour. Compared with the blank extruded rice, it was found by scanning electron microscopy that the cross section pores of extruded rice increased with the increase of the powder content, and the structure tightness decreased. Among them, 20% of extruded rice had tight structure and less cracks. The values of L* and b* in extruded rice of P. eryngii by colorimeter decreased significantly, and a* increased first and then decreased. The water absorption rate and cooking loss rate after cooking increased with the addition of P. eryngii powder, but the expansion rate had no significant effect, and the cooking characteristics of 20% P. eryngii extruded rice were the best. The hardness, elasticity, adhesiveness and chewability of the extruded rice increased with the addition of P. eryngii powder, while the cohesiveness and resilience first decreased and then increased. Starch digestibility, rapidly digestible starch (RDS), slowly digestible starch (SDS) and predicted glycemic index (pGI) also increased with the increase of P. eryngii powder addition, but they were all lower than that of normal rice and blank extruded rice, while resistant starch (RS) content was greater than that of the two groups and increased with the increase. The predicted glycemic index (pGI) value of 20% P. eryngii extruded rice was the lowest 60.18, which was 20.60 lower than that of normal rice, and the content of resistant starch (RS) was the highest. Sensory evaluation showed that the appearance structure, palatability, taste, cold rice texture and comprehensive score of P. eryngii extruded rice decreased with the increase of the amount of P. eryngii powder, while the odor score decreased first and then increased. From the point of view of the score, 20% of P. eryngii extruded rice was 66.75 scores, which was the most acceptable to consumers. 【Conclusion】 20% of extruded rice with P. eryngii was nutrient-rich and had suitable texture indexes. The predicted glycemic index (pGI) was 60.18, which was 20.60 lower than that of normal rice. The nutritional value of extruded rice was significantly improved by adding P. eryngii powder, and the food quality was better.

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    Modeling and Optimization of 3D Printing Process of Pleurotus Eryngii Powder Using Neural Network-Genetic Algorithm
    SU AnXiang, HE AnQi, MA GaoXing, ZHAO LiYan, YANG WenJian, HU QiuHui
    Scientia Agricultura Sinica    2024, 57 (3): 584-596.   DOI: 10.3864/j.issn.0578-1752.2024.03.012
    Abstract119)   HTML14)    PDF (3203KB)(77)       Save

    【Objective】Food 3D printing technology, a promising technology in the field of food, can be affected by multiple factors and thus has problems, such as difficulty in determining printing parameters and poor ability of predicting printing accuracy. This paper aimed to seek out an effective modeling method to optimize 3D printing parameters of Pleurotus eryngii powder and to determine the optimal conditions for 3D printing.【Method】Pleurotus eryngii powder and locust bean gum were adopted as 3D printing ink. Then, based on single-factor experiments, the central composite experimental design was performed to study the influence of four key process parameters - nozzle diameter, printing height, nozzle movement speed and fill density - on the accuracy of 3D printing. In order to optimize 3D printing parameters of Pleurotus eryngii powder, response surface methodology (RSM) and artificial neural network and genetic algorithm (ANN-GA) were employed to achieve different effects.【Result】The determination coefficient (R2), root mean square error (RMSE), relative error (RE), and optimal value of prediction (VOP) of RSM model were 0.8817, 0.2314, 72.73%, and 0.148, respectively; the R2, RMSE, RE, and optimal VOP of ANN-GA model were 0.9389, 0.2269, 33.85%, and 0.215, respectively. The ANN-GA model obtained higher R2, lower RMSE and RE, and was better fitting ability, and higher optimal VOP than RSM model, so ANN-GA model possessed better prediction ability. Compared with RSM, ANN-GA was more suitable for optimization of 3D printing parameters of Pleurotus eryngii powder. The optimal process parameters of 3D printing obtained by ANN-GA, with Pleurotus eryngii as printing ink, included nozzle diameter 1.2 mm, printing height 1.1 mm, nozzle movement speed 24 mm·s-1, and fill density 84%. Experimental verification suggested that the deviation of printed samples by ANN-GA was 0.325, which was superior to the actual printing deviation 0.550 by RSM.【Conclusion】ANN-GA was effective in determining the optimal process parameters of 3D printing and accurate in predicting the accuracy of food 3D printing products. Therefore, ANN-GA could serve as an effective and convenient method for optimizing personalized 3D printing parameters of agricultural products and food.

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    Metabolomic Analysis of Canarium album Fresh Food Quality Differences Based on Sensory Evaluation
    XIE Qian, JIANG Lai, DING MingYue, LIU LingLing, CHEN QingXi
    Scientia Agricultura Sinica    2024, 57 (2): 363-378.   DOI: 10.3864/j.issn.0578-1752.2024.02.011
    Abstract113)   HTML6)    PDF (4135KB)(92)       Save

    【Objective】 This study aimed to identify key metabolites that influence the quality of fresh Chinese olives and to investigate the metabolic mechanisms underlying quality differences. 【Method】 Four Chinese olive varieties were selected as test materials, with Huiyuan as the topgrafting rootstock. The quality of the fruits was evaluated through sensory evaluation. Metabolite identification and analysis of the KEGG pathway were conducted using ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), and the metabolic changes during the ripening process of the fruits were investigated too.【Result】 The results of sensory evaluation of four varieties (lines) of Chinese olive fruits showed significant differences in quality. Tianlan No.1 and Dongshan Changsui exhibited good quality, while Huiyuan and Ziyang No.1 had poor quality. A total of 651 metabolites belonging to 15 types were identified in the Chinese olive fruits of the four varieties (lines). Among these, 277 were primary metabolites of 6 types, and 365 were secondary metabolites of 9 types. Using variable projection and multiple differences, 26 characteristic differential metabolites that influence the quality of fresh Chinese olives were screened. These metabolites included amino acids and their derivatives (6), organic acids (2), lipids (2), and phenolic compounds (16). The phenolic compounds consisted of phenolic acids (3), flavonoids (3), flavonols (2), flavanols (3), and hydrolyzed tannins (5). A metabolic network were established based on the ripening process of Chinese olives to explain the differences in fresh food quality. Chinese olives with good fresh food quality showed a higher accumulation in the biosynthetic metabolic pathway of L-Asparagine and N, N-dimethylglycine, which influenced the taste of fresh food and its resilience. On the other hand, Chinese olives with poor fresh food quality exhibited relatively high levels of hydrolyzed tannins (digalloylchebuloylglucose, galloyl methyl gallate, heterophylliin A), flavonol [morin-3-O-xyloside, quercetin-3-O-(6′-galloyl], Flavan-3-ol [7-O-galloyltricetiflavan, catechin - (7,8-bc) -4α- (3,4-dihydroxyphenyl) - dihydro-2-(3H)-one, catechin-(7,8-bc)-4β-(3,4-dihydroxyphenyl)-dihydro-2-(3h)-one] in the synthesis pathway, which influenced the taste of fresh food and contributed to its bitter taste. 【Conclusion】 The differences in fresh quality of different olives were closely related to the accumulation differences in amino acid and its derivative synthesis pathways, as well as the synthesis pathways of hydrolyzed tannins, flavanols, and flavan-3-ol during their ripening process.

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    Effects of Mannitol on Production Characteristics and ROS Scavenging Ability of Volvariella volvacea Subcultured Strains
    ZHAO FengYun, CHENG ZhiHong, TAN QiangFei, ZHU JiaNing, SUN WanHe, ZHANG WenWei, YUN JianMin
    Scientia Agricultura Sinica    2024, 57 (1): 190-203.   DOI: 10.3864/j.issn.0578-1752.2024.01.013
    Abstract151)   HTML8)    PDF (4861KB)(64)       Save

    【Objective】The aim of this study was to investigate the effects of mannitol on production characteristics and reactive oxygen species (ROS) scavenging ability of Volvariella volvacea subcultured strains, and to explore a simple and effective method for the rejuvenation of V. volvacea degenerated strains. 【Method】The tissue isolation subcultured strains T6, T12 and T19 were obtained by previous study of our research group, and T6 was obtained after 6 successive subculture, while T12 and T19 was obtained after 12 and 19 successive subculture, respectively. The original strain (T0), referred to as V844, was a strain used in commercial agricultural cultivation. The glucose in the traditional potato dextrose agar (PDA) was replaced by mannitol of the same mass, then physiological traits were determined in mycelia. The agronomic characters of fruiting body were measured by adding mannitol to the culture medium. ROS accumulation was reflected using nitrotetrazolium blue chloride (NBT) staining of V. volvacea mycelia, superoxide anion ($\mathrm{O}_{2}^{\bar{.}}$) and hydrogen peroxide (H2O2) content. The expression levels of antioxidant enzyme genes were detected by real-time quantitative PCR (RT-qPCR). The activity of antioxidant enzymes was measured by the kit. The number of nuclei and mitochondrial membrane potential were determined by mycelium staining. The energy indexes were determined by high performance liquid chromatography (HPLC). 【Result】Mannitol treatment had no significant effect on non-degraded strains T0 and T6, but could effectively restore the production characteristics and ROS scavenging ability of degraded strains T12 and T19. After mannitol treatment, the mycelial growth rate of T12 and T19 was increased by 31.46% and 20.99%, respectively, and the mycelial biomass was increased by 97.33% and 76.36%, respectively. The mannitol treatment shortened the production cycle of T12 by 12.24% and increased the biological efficiency by 17.97%, thus restoring it to T0 level. In addition, the mannitol treatment caused T19 to regrow its fruiting body, which had been severely degraded and lost its ability to produce fruiting bodies. Meanwhile, mannitol treatment increased the relative expression of Cu/Zn superoxide dismutase (Cu/Zn-sod) gene in T12 and T19 by 24.64% and 61.54%, respectively, and the relative expression of Mn-sod2 gene by 19.76% and 267.09%, respectively. Similarly, the relative expression of glutathione peroxidase (gpx) gene was up-regulated by 25.67% and 55.82%, respectively. More importantly, the activity of SOD in T12 and T19 increased by 10.79% and 72.32%, and the activity of GPX increased by 16.98% and 103.85%, respectively. The accumulation of ROS in T12 and T19 was significantly reduced by mannitol treatment, in which the $\mathrm{O}_{2}^{\bar{.}}$ content in T12 and T19 decreased by 35.96% and 41.62%, while the H2O2 content decreased by 14.44% and 18.26%, respectively. Furthermore, the mannitol treatment significantly increased the number of nuclei and mitochondrial membrane potential in T12 and T19. Mannitol treatment could increase ATP content in T12 and T19 by 17.08% and 14.55%, and EC value by 4.52% and 0.92%, respectively. 【Conclusion】Mannitol treatment could significantly improve the antioxidant capacity and mitochondrial function of the degenerated strains T12 and T19, and effectively restore their production traits.

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    Effects of Processing Technology on the Amandin Immunoreactivity and Digestive Stability of Apricot Kernel
    LONG FeiFei, ZHANG QingAn, ZHANG ZhiHua
    Scientia Agricultura Sinica    2023, 56 (24): 4930-4943.   DOI: 10.3864/j.issn.0578-1752.2023.24.011
    Abstract81)   HTML8)    PDF (1109KB)(49)       Save

    【Background】In recent years, allergies have become a global health concern, and the number of allergic individuals continues to rise. Nut is one of the common origins of allergies, and apricot kernels, as a common nut containing the allergenic protein amandin, have become one of the most susceptible nuts to allergies. Therefore, allergy removal of nuts has become a research hotspot. The processing of apricot kernels generally involves procedures, such as peeling, debitterizing and drying, and there are no relevant reports on whether their allergenicity will be affected during these processing. 【Objective】The aim of this study was to explore the impact of processing on the allergenicity with the allergenicity, quality and nutritional characteristics of apricot kernels as the evaluation indicators, and to optimize the processing for reducing the allergenicity of apricot kernels, thus providing the theoretical basis and technical support for the processing of low allergenic nuts products of apricot kernels.【Method】Firstly, the methods of Western blotting and ELISA were used to investigate the effects of different peeling, debitterizing and drying methods on the amandin immunoreactivity in apricot kernels. Then, the circular dichroism spectroscopy, extrinsic fluorescence spectroscopy, surface hydrophobicity and zeta potential measurements were used to study the effects of various processing methods on the structure and surface properties of amandin, and to analyze the mechanism of the immune-reactivity changes of amandin. Finally, the vitro simulation digestion experiments were conducted to investigate the digestive stability of amandin in apricot kernels before and after processing, and Western blotting analysis was conducted on the digestion products to further explore the changes in potential allergenicity of apricot kernels.【Result】In terms of allergenicity, the amandin’s immunoreactivity after being peeled by the saturated hot air and blanched decreased by 8.41% and 13.15%, respectively. After being quickly debitterized by ultrasound, the amandin’s immunoreactivity decreased by 6.79%. Blanching debitterizing had no significant effects on its immunoreactivity. After natural drying and hot air drying, the immune reactivity of the amandin significantly increased by 4.58% and 2.81%, respectively (P<0.05). Based on the impact of processing on the quality and nutritional characteristics of apricot kernels, those suitable processing methods to decrease the allergenicity of apricot kernels were optimized like the saturated hot air peeling, ultrasonic rapid debitterizing and hot air drying, and the immune reactivity of apricot kernels decreased by 15.03% under the optimal conditions. In terms of the structure of amandin, the secondary structure composition, tertiary structure, surface hydrophobicity and zeta potential have undergone certain changes during the processing. Among them, the ultrasound rapid debitterizing significantly changed the tertiary structure of amandin and enhanced its surface hydrophobicity (P<0.05), resulting in the most significant decrease in its immune reactivity. The digestive stability of the amandin after processing was significantly reduced, and the accelerated degradation rate of structures was related to the specific antigen antibody reactions in allergenic proteins, leading to a further decrease in the potential allergenicity of apricot kernels.【Conclusion】Different processing steps could affect the allergenicity of apricot kernels by changing the structure of amandin, i.e. the reasonable processing methods could be used to reduce the allergenicity of apricot kernels.

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    Mechanism of Hydration Environment/Magnetic Field Effects on the Oxidative Stability of Myoglobin
    DENG YuShi, XIA MinQuan, MA Jing, ZHOU YuanHua, SUN WeiQing
    Scientia Agricultura Sinica    2023, 56 (22): 4523-4531.   DOI: 10.3864/j.issn.0578-1752.2023.22.013
    Abstract110)   HTML6)    PDF (1682KB)(84)       Save

    【Objective】To investigate the mechanism of action of hydration environment affecting the oxidative stability of myoglobin (Mb) in the presence of a magnetic field, and to provide a basis for improving the oxidative stability of Mb. 【Method】Two magnetic field environments of low intensity (3 mT) and high intensity (12 mT) were set up at 4 ℃, the magnetic field treated Mb aqueous solution, Mb powder, and deionized water (the magnetic field treated deionized water and then dissolved Mb), respectively, and the magnetic field treatment time was 1 h. The Mb aqueous solution without magnetic field treatment was used as the control. The oxidative stability properties of Mb were analyzed by the relative content of high iron myoglobin, heme iron content and the variation of UV absorption bands, while the changes of Mb secondary structure, tertiary structure and porphyrin iron structure were analyzed by circular dichroism, and Raman spectroscopy and fluorescence spectroscopy techniques were employed to investigate the mechanism of the effect of magnetic field on the oxidative stability of Mb. 【Result】Both magnetic field treatment of Mb powder directly and magnetic field treatment of solvent water followed by dissolution of Mb had no significant effect (P>0.05) on the relative content of methemoglobin, while both 3 mT and 12 mT magnetic field treatment of Mb aqueous solution significantly increased the relative content of methemoglobin. The results of heme iron content and heme Shore band UV absorption showed that the heme porphyrin ring structure was sensitive to the magnetic field environment, and the magnetic field of different intensities had significant damage to the Mb heme structure, while the high intensity magnetic field environment had relatively greater damage to the porphyrin ring structure. Mb tertiary and secondary structure results showed that both 3 mT magnetic field treatment of solvent water before dissolving Mb, and 3 mT and 12 mT magnetic field treatment of Mb aqueous solution significantly promoted the unfolding of Mb secondary structure and oxidative damage of tryptophan and tyrosine residues of side chain groups. Raman spectroscopy results showed that 12 mT magnetic field treatment of Mb aqueous solution induced the cross-linking of Mb through disulfide bonds. 【Conclusion】Hydration in Mb aqueous solution directly affected the effect of magnetic field on the oxidative properties of myoglobin, and magnetic field treatment promoted the oxidation of Mb central iron as well as heme porphyrin ring, probably because the magnetic field changes the physical properties of water molecules, such as dielectricity and degree of ionization, as well as the hydrogen bonding state between Mb and water, which further affected the structure of Mb with the unfolding of α-helix structure and the exposure of side chain groups, accelerating the destruction of heme structure and loss of heme iron, and promoting the oxidation of central iron.

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    Effects of Different Salt Ions on the Gel Properties and Molecular Interactions of Quinoa Protein
    FENG Xiao, WU ChaoSheng, YANG YuLing, FU LiXiao, CHEN LongWei, TANG XiaoZhi
    Scientia Agricultura Sinica    2023, 56 (21): 4318-4329.   DOI: 10.3864/j.issn.0578-1752.2023.21.014
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    【Objective】This research studied the effects of different salt ions on the gel properties of quinoa protein, and explored its molecular mechanisms, so as to provide a theoretical basis for the processing of quinoa protein gels.【Method】Quinoa protein was extracted by alkali extraction and acid precipitation. Quinoa protein solution (20%, w/v) was prepared at pH 7.0. NaCl, CaCl2, CaSO4 and MgCl2 was added in quinoa protein solution till the concentration was 50 mmol∙L-1, and then the solution was heated in a water bath to prepare quinoa protein gels. The effects of salt ions on the texture, water retention, color properties and water distribution of quinoa protein gels were analyzed. Meanwhile, the effects of salt ions on the microstructure and rheological properties of quinoa protein gels were studied by scanning electron microscopy and rheometer. The effects of salt ions on the molecular interactions and secondary structure of protein gels were also analyzed.【Result】The addition of salt ions significantly decreased the hardness and water holding capacity, while increased the springiness of quinoa protein gels under pH 7.0. Quinoa protein gels with MgCl2 showed the lowest hardness and water holding capacity. NaCl addition had no significant influence on the color properties of protein gels. However, the addition of bivalent salt ions significantly improved the lightness and whiteness of quinoa protein gels, and their whiteness increased from 59.62 to 67.80 with the addition of CaCl2. Furthermore, the addition of salt ions promoted granular aggregation of quinoa protein, which made the gel network structure become coarse. Coarse and larger gaps were observed in the microstructure of quinoa protein gels when divalent salt ions were added. Meanwhile, compared with blank gels and gels added with NaCl, the addition of divalent salt ions significantly decreased the content of disulfide bond, and weakened the electrostatic interactions within quinoa protein gels. Furthermore, the addition of salt ions decreased the contents of β-sheets and β-turns, increased the contents of α-helix and random coil, which affected the orderliness of protein secondary structure.【Conclusion】Under neutral conditions, the gel properties of quinoa protein and microstructure of gels were affected by the presence of different salt ions to various degrees. Compared with the gel prepared with NaCl, quinoa protein gels with the same concentration of CaCl2, CaSO4, and MgCl2 showed rougher microstructure, lower gel hardness and water holding capacity, as divalent salt ions significantly decreased the disulfide bond content and weakened the electrostatic interactions within quinoa protein gels.

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    Effects of Oat Bran Flour and Tartary Buckwheat Bran Flour on Structure, Cooking Quality and Digestive Characteristics of Wheat Noodles
    PENG Pai, WANG XiaoLong, MA Lan, ZOU XiaoYang, MA QianYing, ZHANG XinYu, LI XiaoPing, HU XinZhong
    Scientia Agricultura Sinica    2023, 56 (20): 4102-4114.   DOI: 10.3864/j.issn.0578-1752.2023.20.014
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    【Objective】 This study aimed to explore the effects of oat bran flour and Tartary buckwheat bran flour addition on the structure, quality and digestive characteristics of wheat noodles, so as to confirm their application values in the production of wheat-based food products. 【Method】 Three types of noodles were prepared with three recombinant flours containing 30% oat bran flour + 70% wheat flour, 30% Tartary buckwheat bran flour + 70% wheat flour, and 15% oat bran flour + 15% Tartary buckwheat bran flour + 70% wheat flour, respectively, with pure wheat noodle as control. The cooking quality, sensory quality and digestive characteristics of different noodles were determined and compared firstly. Then the structural characteristics of protein and starch in noodles were analyzed and compared by Fourier infrared spectrometer, X-ray diffractometer, Size-exclusion high performance liquid chromatography, Scanning electron microscope and Laser confocal scanning microscope, respectively. 【Result】 The introduction of oat bran flour and Tartary buckwheat bran flour weakened the cooking and sensory quality of noodles, but improved the starch digestion resistance of noodles. The noodle containing 30% oat bran flour showed the lowest glycemic index (GI) of 47.9 among all the noodles. Protein denaturation and reconstruction during noodle cooking facilitated the binding between protein and other molecules higher proportion α-helix and lower proportion β-sheets was found in the protein of cooked oat bran noodles, which led to the transformation of protein aggregates into a loose and extended protein network that enforced the wrapping effect of protein to starch. After cooking, the starch crystal in noodles was destroyed, leading to the reduced orderliness. The addition of oat bran flour and buckwheat bran flour promoted the starch-lipid interactions in noodles, which contributed to the formation of resistant starch. Compared with buckwheat bran four, oat bran flour was more beneficial to maintaining the short-range order of starch and promoting the formation of more V-type crystals in noodle. In addition, the high content of β-glucan in oat bran flour further contributed to the interactions between starch and other molecules. 【Conclusion】 The addition of oat bran flour and Tartary buckwheat bran flour decreased the cooking and sensory quality of wheat noodle, but reduced the GI value of the noodle. The noodles containing 30% oat bran flour was a low GI food. The addition of oat bran flour and buckwheat bran flour in noodles contributed to the formation of resistant starch deriving from complex starch-protein and starch-lipid interactions during starch gelatinization. Oat bran flour was conductive to maintaining the thermal stability of protein network and improving the digestion resistance of starch in noodle by enhancing the interactions between starch and other molecules.

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    Effects of Different Drying Methods on the Quality Characteristics of Dried Zanthoxylum armatum Leaves
    WANG AnNa, WANG Yun, PENG XiaoWei, WU YuFang, KAN Huan, LIU Yun, QUAN Wei, LU Bin
    Scientia Agricultura Sinica    2023, 56 (18): 3655-3669.   DOI: 10.3864/j.issn.0578-1752.2023.18.013
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    Objective】In order to ensure improved drying quality of Zanthoxylum armatum (Z. armatum) leaves with low processing cost and high nutritional value, the effects of different drying methods on the quality of Z. armatum leaves were studied, so as to provide a reference basis for its development and utilization. 【Method】With Z. armatum leaves as test materials, 5 different drying methods were set, including natural drying (ND), hot air drying (AD), heat pump drying (PD), vacuum drying (VD), and vacuum freezing drying (FD). The effects of 5 different drying methods on their drying characteristics, functional characteristics, microstructure, content of polyphenol, flavonoid, protein, fat, and total sugar, as well as antioxidant capacities and volatile compounds, were investigated. 【Result】The moisture ratios of Z. armatum leaves under 5 different drying methods all exhibited an exponential downward trend, and the time required to reach the end of drying was 32, 7, 6, 16 and 28 h for ND, AD, PD, VD and FD, respectively. During the drying period, the faster the water diffusion, the greater the drying rate and the shorter the elapsed time, and the drying rate was PD>AD>VD>FD>ND. The effects of different drying methods on the color of Z. armatum leaves was VD>ND>PD>AD>FD, where AD and FD could better retain their chlorophyll content at 12.74 and 12.85 mg∙g-1, respectively. The microstructure showed that temperature had a significant effect on the internal structure of Z. armatum leaves, which was more seriously damaged by high temperature, and FD exhibited a porous structure with better water-holding capacity of 5.85 g∙g-1. ND had the highest retention of sugars at 6.53 g/100 g, resulting in a higher water-solubility of 35.93%. PD retained its protein and fat better, with content of 2.43 and 4.86 g/100 g, respectively. The retention of polyphenols and flavonoids in dried Z. armatum leaves was high, with polyphenol content ranging from 72.16 to 109.50 mg∙g-1 and flavonoid content ranging from 45.60 to 82.23 mg∙g-1, where AD and FD were high and relatively close in polyphenol and flavonoid content. The scavenging capacities of DPPH∙, ABTS+∙ and the power of FRAP reduction were FD>AD>PD>ND>VD, with positive correlation between the content of polyphenols, flavonoids and antioxidant capacities. Simultaneously, the volatile compounds were determined by headspace solid-phase microextraction-mass spectrometry coupled with gas chromatography-mass spectrometry, and a total of 49 species were detected, which could be classified into seven categories according to structures, including olefins, ketones, aldehydes, esters, alcohols, benzenes, and phenols. It was found that the types, numbers, and relative content of volatile compounds in Z. armatum leaves varied under 5 different drying methods, among which olefins were dominant, with a total of 26 species and relative content ranging from 58.02% to 75.18%.【Conclusion】Based on the comprehensive quality indexes of materials and actual operation cost, it was found that AD was more suitable for drying Z. armatum leaves, with higher efficiency, lower cost, as well as relatively better quality of color and antioxidant capacities.

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    Effect of Heat Treatment on the Warmed-Over Flavor of Nanjing Water-Boiled Salted Duck Detected by HS-SPME-GC-MS Technology and Electronic Nose
    WU ShiHao, HUANG TianRan, HUANG Ming
    Scientia Agricultura Sinica    2023, 56 (17): 3435-3451.   DOI: 10.3864/j.issn.0578-1752.2023.17.016
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    【Objective】 By using flavor detection technology, the effect of heat treatment on Nanjing water-boiled salted duck’s warmed-over flavor (WOF) was investigated, and the main components of warmed-over flavor were identified. The study could fill the gap in research on warmed-over flavor of Nanjing water-boiled salted duck, as well as provide a basis for controlling the odor associated with poultry processing. 【Method】 The raw materials for the Nanjing water-boiled salted duck were 12 cherry valley duck legs, washed, dry pickled, wet pickled, cooled, and boiled. The samples were vacuum packed in high-temperature retort pouches and randomly divided into four groups after cooling. In order to examine the changes in volatile odor substances in water-boiled salted ducks after heat treatment, one group was used as a control without heat treatment, and the other three groups were heated at different temperatures (80 ℃ 50 min, 100 ℃ 30 min, and 121 ℃ 15 min). By using HS-SPME-GC-MS in combination with electronic nose and sensory evaluation, the effect of heat treatment on Nanjing water-boiled salted duck's warmed-over flavor was studied by cluster analysis and PLS-DA. 【Result】 Under different heat treatment conditions, Nanjing water-boiled salted duck contained different volatile flavor substances. Sensory evaluation showed that the highest warmed-over flavor was found in the 121 ℃ heat treatment group, followed by 100 ℃ and 80 ℃ group, and the best flavor was found in water-boiled salted duck without heat treatment. A total of 78 flavor compounds were detected in the four groups, mainly including aldehydes, ketones, hydrocarbons, alcohols, nitrogenous sulfur, and benzene. These 78 flavor substances were analyzed for OAV, and 22 active odors were detected with OAV>1, among these 22 active odor substances, cluster analysis showed that Valeraldehyde, 2-Heptanone, Decanal, Dodecanal, Octanal, Hexanal, Heptanal, Nonanal, 2,5-Octanedione, 1-Octen-3-ol and 2-Pentylfuran were the most abundant in the 121 ℃ group. Nonanal, Octanal, Valeraldehyde, 1-Octen-3-ol, and 2-Pentylfuran were found to have VIP>1 and the highest content at 121 ℃ in the OPLS-DA analysis (P<0.05). 【Conclusion】 It has been found that heat treatment at 121 ℃ increased oxidative degradation of lipids in water-boiled salted duck, significantly reduced the content of representative aroma substances, and increased the amount of representative odor substances. Nanjing water-boiled salted duck’s warmed-over flavor mainly consisted of Nonanal, Octanal, Valeraldehyde, 1-Octen-3-ol, and 2-Pentylfuran.

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    Effect of Boiling Coconut Water on Flavor Formation of Wenchang Chicken
    WU YuCan, ZHANG ZiHan, ZHAO GuiPing, WEI LiMin, HUANG Feng, ZHANG ChunHui
    Scientia Agricultura Sinica    2023, 56 (16): 3199-3212.   DOI: 10.3864/j.issn.0578-1752.2023.16.012
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    【Objective】The aim of this study was to clarify the quality characteristics of Wenchang chicken cooked with coconut water, so as to provide an effective basis for the research on the interaction mechanism of Wenchang chicken and coconut water components and the standardized production.【Method】With Wenchang chicken and Hainan green coconut as the main raw materials, the odor substances of Wenchang chicken, Wenchang chicken breast meat, and chicken leg meat cooked with coconut water were analyzed and compared using an electronic nose and gas chromatography-mass spectrometry (GC-MS), combined with odor activity value (OAV) and principal component analysis (PCA). The taste substances of chicken breast meat and chicken leg meat were analyzed using electronic tongue, free amino acid, and nucleotide detection techniques. The physical and chemical indexes of chicken and coconut water, as well as the cooking loss and texture indexes of coconut-boiled chicken and water-boiled chicken, were determined to clarify the changes in the quality characteristics of Wenchang chicken after cooking with coconut water.【Result】The protein content in chicken leg meat was 21.0 g/100 g, and the fat content was 3.08 g/100 g. The protein content in chicken breast meat was 23.6 g/100 g, and the fat content was 1.29 g/100 g. The content of reducing sugar in coconut water was 4.75 g/100 g. The cooking loss of chicken cooked with coconut water was the highest compared with that boiled with water, and there was no significant correlation between the two texture indicators (P>0.05). After cooking with coconut water, five new aldehydes were produced in the chicken, namely 2-heptanal, (E)-2-octenal, (E)-2-nonenal, 2, 5-dimethyl benzaldehyde, and 2-undecenal. The electronic nose was able to distinguish the volatile substances in boiled chicken legs from those in coconut water. After cooking with coconut water, the content of sweet amino acids in chicken legs and chicken soup increased, but the content of savory amino acids in boiled chicken legs, chicken breasts, and broth was higher than that in chicken cooked with coconut water. The contents of 5'-AMP, 5'-IMP, and 5'-GMP in chicken cooked with coconut water were higher than those in boiled chicken.【Conclusion】The fat content in the chicken leg and protein content in the chicken breast differed in various parts of the Wenchang chicken. Boiling Wenchang chicken with coconut water increased the nucleotide content in the muscles and the free amino acid content in the chicken leg meat, significantly enhancing the taste. Boiling Wenchang chicken with coconut water increased the types of aldehydes in the thigh meat, and resulted in better flavor formation than the breast meat.

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    Influencing Factors of Gluten Network Structure Analysis Using Confocal Laser Scanning Microscopy
    JIANG JiKai, ZHANG YingQuan, GUO BoLi, YANG JingJie, HUANG LuYao, LI Ming, ZHONG Geng
    Scientia Agricultura Sinica    2023, 56 (14): 2787-2797.   DOI: 10.3864/j.issn.0578-1752.2023.14.013
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    【Objective】The thickness of sample slices, the concentration of staining solution and the staining time are the key factors influencing the results of gluten network structure analysis using confocal laser scanning microscopy (CLSM). The aim of this study was to investigate the effects of the slice thickness, the staining solution concentration and the staining time on the CLSM results of gluten network structure, and the optimal slice thickness and staining conditions for the dough structure analysis were selected, so as to provide a technical support for the studies on dough structure and/or its final products. 【Method】Two wheat varieties, i.e., Zhengmai 366 (Z366) and Xiaoyan 22 (X22) with different wet gluten indexes, were selected as raw materials, which were milled and made into dough, respectively. Then, the dough samples were frozen for 0 and 1 day. The dough slice thickness was set as 10, 14 and 20 μm, respectively. Meanwhile, two concentrations of staining solution (0.001%+0.01%, 0.025%+0.25%) using Rhodamine B (RDB) and fluorescein isothiocyanate (FITC) were prepared. The staining time was set for 1, 10 and 20 min, respectively. 【Result】The sample slice with 10 μm thickness showed the best and clearest image for both doughs of Z366 and X22. Besides, under this slice thickness, the gluten network of the dough frozen stored for 0 day showed the most obvious difference compared with that for 1 day (P<0.01). Additionally, under low-concentration staining agent (0.001%+0.01%), the clearer the results of gluten network structure were obtained with longer staining time. Oppositely, under the high-concentration staining agent (0.025%+0.25%), the slice with a staining time of 1 min showed the most rational results on the gluten network structure, whereas the result on the slice with a staining time of 10 min was the worst. 【Conclusion】The gluten network structure of dough with different protein content and freezing treatments demonstrated more differences when the thickness of dough slices was 10 μm, indicating the gluten network structure of different samples could be distinguished obviously. Under the selected thickness, the gluten network structure of 20 min stained with low-concentration mixed staining agent showed the best effect if time-consuming was not considered. Moreover, the high-concentration staining for 1 min was time-saving and better for observing the structure of starch granules.

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    Aroma Characteristics of Foxtail Millet Varieties from Different Ecological Regions by Analysis of SDE-GC-MS Combined with OPLS-DA
    LI ShaoHui, ZHAO Wei, LIU SongYan, LI PengLiang, ZHANG AiXia, LIU JingKe
    Scientia Agricultura Sinica    2023, 56 (13): 2586-2596.   DOI: 10.3864/j.issn.0578-1752.2023.13.012
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    【Background】The foxtail millet production areas in China are divided into four regions: the Northeast China region, the North China region, the Inner Mongolia plateau region, and the Northwest China region. The regional trials aimed to screen germplasm resources with good genetic traits. However, good growth genetic traits and foxtail millet grain appearance phenotypes do not necessarily have good culinary quality and aroma characteristics, especially the aroma characteristics largely affect its production and downstream industries. Simultaneous distillation extraction (SDE) is a pretreatment method that simulates the cooking process of porridge and is suitable for the aroma analysis of foxtail millet.【Objective】The aim of this study was to clarify the aroma characteristics of cereal germplasm resources in different ecological regions, so as to promote sensory-oriented breeding-processing industrial practices.【Method】Simultaneous distillation extraction-gas chromatography-mass spectrometry (SDE-GC-MS) combined with odor activity value (OAV) method was used to analyze the differences in aroma components of foxtail millet in different regions of China.【Result】 A total of 81 volatile substances were detected in 12 foxtail millet varieties from four ecological regions, 25 aldehydes, 6 alcohols, 4 phenols, 11 ketones, 11 hydrocarbons, 13 benzene-containing derivatives, 4 acids, and 7 others. The comparison of the results showed that the volatile substance subclasses were similar in different regions, but the contents of the components were different. Thirty-seven volatile components with literature-accessible odor characterization were labeled, and 23 contributing aroma compounds with OAV > 1 were identified in the 12 foxtail millet varieties. The effective discrimination model of the cereal regional test was established by orthogonal partial least squares discrimination analysis (OPLS-DA). Then, the 12 foxtail millet varieties were classified into three categories, and 18 compounds with VIP>1 were screened out: hexanal, heptanal, (Z)-2-heptenal, benzaldehyde, (E,E)-2, 4-decadienal, 2,4-decadienal, nonane, tetradecanoic acid, (Z,Z)-9, 12-octadecadienoic acid, pentadecanoic acid, n-hexadecanoic acid, 2-methoxy-4-vinylphenol, 2, 4-bis(1, 1-dimethylethyl)-phenol, 2, 5-bis(1, 1-dimethylethyl)-phenol, 1-heptanol, nerolidol, 2-pentyl-furan, and hexadecanoic acid methyl ester, which could be used to distinguish the differences between different samples.【Conclusion】 SDE-GC-MS combined with OAV identification analyzed the flavor components and characteristics of key aroma compounds of foxtail millet from different ecological regions, and the OPLS-DA model screened 18 VIP compounds that distinguished the flavor differences of foxtail millet from different samples and ecological regions. The results of the study provided data references for understanding the differences in flavor characteristics of foxtail millet grown in different regions of China, and for a basis of flavor-oriented foxtail millet variety selection, breeding, and processing.

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    The Optimal Fermentation Technique of Radix puerariae Residues by Aspergillus niger for Dietary Fiber Modification and the Consequent Changes of Physicochemical and Functional Properties of Dietary Fibers
    FU HuiZhen, DENG Mei, ZHANG MingWei, JIA XuChao, DONG LiHong, HUANG Fei, MA Qin, ZHAO Dong, ZHANG RuiFen
    Scientia Agricultura Sinica    2023, 56 (12): 2380-2394.   DOI: 10.3864/j.issn.0578-1752.2023.12.012
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    【Objective】 The objectives of the present study were to screen the microbial species suitable for modification of dietary fiber (DF) of Radix puerariae residues, to establish the optimum fermentation conditions, and to clarify the changes of microstructure, physicochemical and functional properties of Radix puerariae residues DF before and after fermentation modification.【Method】Aspergillus niger, Rhizopus oryzae, Trichoderma viride and Bacillus subtilis subsp were used to ferment Radix puerariae residues, respectively, and the most effective microbial strain was screened by comparing the SDF yield of Radix puerariae residues. The single factor experiments were carried out to screen the factors influencing DF modification. Then, the Box-Benhnken central composite experiment was designed to establish the optimum DF modification conditions of Radix puerariae residues with the SDF yield as the index of evaluation. The insoluble DF (IDF) and SDF of Radix puerariae residues before and after modification under optimal fermentation conditions were extracted by enzymatic hydrolysis method. The microstructures of IDF and SDF were observed by scanning electron microscope, and the physicochemical (water holding, oil holding, and water swelling capacity) and functional properties (adsorption capacity of glucose, sodium cholate and cholesterol) of IDF samples from unfermented and fermented Radix puerariae residues were analyzed.【Result】The fermentation of Radix puerariae residues, by A. niger, R. oryzae or T. viride all increased the SDF yield, and A. niger was the most effective species. However, the fermentation with B. subtilis subsp had no significant effects on the SDF yield. Therefore, A. niger was selected as the most suitable strain for Radix puerariae residues fermentation. The optimal fermentation condition determined by response surface optimization was as follows: The ratio of solid-liquid was 1:5.8 (m/v), the inoculation volume was 4.9% (v/v), the fermentation time was 100 h, and the fermentation temperature was 24.9 ℃. Under this condition, the yield of SDF increased from 6.34% to 13.75%, while the ratio of IDF/SDF decreased from 6.14 to 2.83. Both IDF and SDF extracted from fermented Radix puerariae residues by A. niger showed more porous microstructure than those from unfermented Radix puerariae residues. Fermentation of Radix puerariae residues increased the water holding and swelling capacity of its IDF by 20 percent approximately, while it showed no significant effects on the oil holding capacity. In addition, after fermentation, the adsorption capacity of IDF of Radix puerariae residues for glucose increased by 70%, and the adsorption capacity for cholesterol increased by 44% and 28% at pH 2.0 and pH 7.0, respectively. 【Conclusion】 A. niger could modify DF of Radix puerariae residues more effectively than other 3 microbial strains. Under the fermentation condition, the SDF yield of Radix puerariae residues increased by 2.17 times after modification by A. niger, and the physicochemical and functional properties of its IDF were also improved significantly.

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    Effects of nuoB on the Biofilm Formation and Cellular Metabolism of Meat-Borne Pseudomonas fragi During Chilled Storage
    WU YaJie, TAN Song, CHEN YuPing, NIU AJuan, LIU YuXin, WANG GuangYu, XU XingLian, QIU WeiFen
    Scientia Agricultura Sinica    2023, 56 (11): 2172-2185.   DOI: 10.3864/j.issn.0578-1752.2023.11.011
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    【Objective】This paper focused on the impacts of nuoB on the biofilm formation and cell metabolism in Pseudomonas fragi (P. fragi), so as to further reveal the regulatory mechanism of nuoB in the spoilage of chilled meat contaminated with P. fragi, and to provide a theoretical basis for developing effective preservation system of chilled meat. 【Method】P. fragi NMC25 and its nuoB-mutant strain were used in the present study, and the differences in the spatial structure of biofilms were observed by confocal laser scanning microscopy (CLSM). The changes in biofilm composition were tested by the cell enumeration and the analysis of the extracellular polymeric substances. In addition, the ultra-high performance liquid chromatography coupled with mass spectrometry (UHPLC-MS/MS) was employed to investigate the alterations of nuoB-related metabolite abundance. 【Result】CLSM images showed that cells in the biofilms of wild-type strains cultivated in situ was highly dense, nematic ordering, whereas ΔnuoB displayed relatively disorganized and sparse arrangement. Additionally, cell enumeration revealed insignificant differences between the wild-type and mutant biofilms regardless of the difference of culture medium. The result indicated that the mutants did not change significantly in their ability to grow as biofilm on the surface of TSA or meat sample. For extracellular polymeric substances from biofilms in situ, the protein and carbohydrate contents of ΔnuoB were significantly higher (P<0.01, P<0.05, respectively) than those of wild-type strains, indicating that nuoB affected the secretion of extracellular polymers by P. fragi. The metabolomics results revealed a clear separation between the wild and mutant groups in an orthogonal partial least squares discriminant analysis model (R2X=0.481, R2Y=0.977, Q2=0.909), which suggested that the metabolites of the mutants had changed markedly. In the model, differentially expressed metabolites were screened, including 2-hydroxycinnamic acid, L-tyrosine, L-phenylalanine, DL-tryptophan, 17(S)-HETE, and 5-OxoETE. Pathway mapping analysis was conducted based on the chosen candidates. In total, the major metabolic pathways included fatty acid biosynthesis, unsaturated fatty acid biosynthesis, riboflavin metabolism, 2-oxocarboxylic acid metabolism, purine metabolism, cyanogenic amino acid metabolism, and phenylalanine metabolism. 【Conclusion】The disruption of nuoB stimulated significant variations in the spatial structure of the P. fragi biofilm grown in situ, promoting the biosynthesis of extracellular polymeric substances and affecting intracellular metabolic pathways, such as carbon, nucleotide, lipid, and amino acid metabolism.

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    Fractionation Effect of Stable Carbon and Nitrogen Isotope Ratios in Yak Dairy Products Processing
    LI JiRong, LIU Xin, WANG Jun, CAO XiaoGang, CI Dun
    Scientia Agricultura Sinica    2023, 56 (10): 1982-1993.   DOI: 10.3864/j.issn.0578-1752.2023.10.013
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    【Background】Stable isotope fingerprinting technology has been widely adopted in the origin traceability study of dairy products. However, most of them are focused on comparing the differences between the stable isotopes of raw milk and milk products. Nevertheless, the fractionation effect of stable isotopes on dairy products processing and the application of stable carbon and nitrogen isotopes for origin tracing of yak dairy products are still unclear.【Objective】In this study, yak yogurt and yak milk dregs were used as the study subjects to determine the changes in stable carbon and nitrogen isotope and the fractionation coefficients and correlations of yak dairy products at key points during processing, to investigate the stable carbon and nitrogen isotope characteristics of yak dairy products from different origins, so as to provide the theoretical and technical supports for origin traceability of yak dairy products.【Method】A total of 196 samples were collected from the Nerong and Jiali counties of Nagqu City, Tibet Autonomous Region, obtain five key sampling points for yogurt processing (yak milk, yak milk boiled for 5 min, sample after strain addition, fermentation at 40 ℃ for 6 h, and yogurt) and four key sampling points for milk dregs processing (yak milk, skimmed yak milk, skimmed yak milk boiled for 10 h, and milk dregs). The stable carbon and nitrogen isotope ratios were determined using an elemental analysis isotope ratio mass spectrometer (EA-IRMS). The differences and correlations between the stable carbon and nitrogen isotopes at the key sampling points for yogurt and milk dregs processing were determined using one-way ANOVA comparative analysis and Pearson correlation analysis, respectively. Furthermore, the differences in stable carbon and nitrogen isotopes between yogurt and yak milk and milk dregs and yak milk with different origins were determined using a two-factor ANOVA.【Result】The fractionation of stable carbon and nitrogen isotope during yogurt processing was as follows: δ13Cyak milk 13C40 ℃ fermentation for 6 h, yak yogurt 13Csamples after adding strain, fractionation coefficient between 0.9996 and 1.0009, ΔYak milk-yak yogurt was 0.48‰; δ15Nboiling 5 min yak milk, 40 ℃ fermentation for 6 h, yak yogurt15Nyak milk, fractionation coefficient was between 0.9993 and 1, and ΔYak milk-yak yogurt was -0.61‰. The correlations between the stable carbon and nitrogen isotopes at some key sampling points were significant. During milk dregs processing, δ13Cyak milk, boiled 10 h skimmed sample, yak milk dregs13CSkimmed yak milk, fractionation coefficient was between 0.9995 and 1.0005, ΔYak milk-yak dregs was 0. A significantly negative correlation was observed in δ13C at some key sampling points, while no significant difference was observed in δ15N for each key point sample and the fractionation values were 0. The stable carbon and nitrogen isotopes of dairy products from different origins significantly differed, with δ13C and δ15N being enriched in yak dairy products from Nerong County compared to Jiali County.【Conclusion】The fractionation of δ13C and δ15N was observed during yak dairy products processing. The addition of strains, fermentation, and centrifugal defatting processes resulted in different δ13C ratios, while heating induced changes in the sample δ13C and δ15N. Although stable isotope fractionation occurred during yak dairy products processing, its influence was less than the origin. Therefore, the stable carbon and nitrogen isotopes could be applied to trace the origin of yak dairy products.

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    The Mechanism of Effects of Konjac Gum on the Gel Property and Water Holding Property of Pork Myofibrillar Protein Based on Phase Separation Behavior and Moisture Stabilization
    LUO Cheng, WANG Huan, CHEN YinJi, LI Chao, ZHUANG XinBo
    Scientia Agricultura Sinica    2023, 56 (9): 1775-1786.   DOI: 10.3864/j.issn.0578-1752.2023.09.013
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    【Objective】 The purpose of this experiment was to study the effects of konjac gum on the microstructure and phase-separated structure of pork myofibrillar proteins, and then to explain the regulation mechanism of konjac gum on the gel property and water holding property of myofibrillar proteins. 【Method】 The simulated system with different ratios of konjac gum and myofibrillar protein was used to measure the texture property, stress and strain during fracture deformation, the water distribution and water holding capacity of the composite gel, and to observe the phase separation behavior of konjac gum and myofibrillar protein and the microstructure of myofibrillar protein gel network. 【Result】 When the addition ratio of konjac gum was less than 0.8%, the gel strength, final value of storage modulus and stress at fracture deformation of the composite protein gels significantly increased to 179.21 g, 1 192 Pa and 9 139.37 Pa respectively with the increase of the addition ratio (P<0.05). When the addition ratio of konjac gum was greater than or equal to 0.8%, the gel strength, storage modulus, stress and strain at fracture deformation of the composite protein gels significantly decreased to 83.03 g, 566 Pa, 4 964.07 Pa and 0.64 (P<0.05) respectively with the increase of the addition ratio. Low-field NMR results showed that the relaxation time and the percentage of free water in the composite gel system of immobilized water decreased significantly (P<0.05) with the increase of the addition ratio of konjac gum less than 0.8%, while the percentage of immobilized water increased significantly (P<0.05), and the water holding capacity of the composite gel increased significantly from 67.18% to 80.47% in the control group (P<0.05). In contrast, the high percentage addition of konjac gum (greater than or equal to 0.8%) significantly increased the relaxation time and the percentage of free water in the immobilized water (P<0.05), while the percentage of immobilized water significantly decreased (P<0.05), and the water holding capacity significantly decreased to 55.24% (P<0.05). Paraffin sections showed konjac gum was embedded in the composite protein gel backbone in a physically filled form with many cavities of various sizes and shapes. Scanning electron microscopy showed that the cavities and gullies in the protein gel network structure of the control group were filled with many moisture phases. The addition ratio of konjac gum less than 0.8% could reduce the interlocking water gullies in the protein network structure and make the protein gel network structure denser and more homogeneous. The high addition of konjac gum (greater than or equal to 0.8%) increased the number and volume of water gullies in the system, resulting in a looser microstructure of the composite gel. The results of image processing analysis showed that the fractal dimension of the composite protein gel network structure with 0.4% konjac gum was the highest (P<0.05), and the lowest (P<0.05) with the lacunary value of 0.264.【Conclusion】The low concentration of konjac gum on myofibrillar protein gel property and water-holding property had a significant improvement effect, but the upper limit of the addition of konjac gum ratio was 0.8%, because a high percentage of the addition (greater than or equal to 0.8%) would make the composite protein gel texture deteriorated.

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    Preparation of Ultrasound-Assisted Zein Ethylene Scavenger Film and Its Preservation Property of Bananas
    FAN Xin, LI YuXin, KUANG JiWei, YANG Ting, LIU MiaoMiao, CAO YunGang, HUANG JunRong
    Scientia Agricultura Sinica    2023, 56 (8): 1574-1584.   DOI: 10.3864/j.issn.0578-1752.2023.08.012
    Abstract171)   HTML25)    PDF (1605KB)(83)       Save

    【Objective】 Ethylene is an important plant hormone that has a key influence on the quality and shelf life of fruit. In this study, zein was modified to transform into a stretched structure and consequently expose its internal active functional groups by the high-field intensity ultrasound treatment (HIU). Numerous functional groups (-SH) exposed in modified zein film could rapidly react with ethylene via a click reaction, resulting in an extended shelf life of the fruit. 【Method】 The 5 g zein was dissolved in acetic acid-DI water (4:1) solution. The zein solutions were sonicated for 0, 5, 15, and 30 min at an ultrasonic power of 400 W and dried in a drying oven at 40℃ for 24 h to obtain the zein-0 film, zein-5 film, zein-15 film, and zein-30 film. The structures of zein before and after HIU treatment were analyzed by circular dichroism spectroscopy, endogenous fluorescence, particle size potentiometer, and scanning electron microscope. The mechanical and ethylene adsorption properties of zein-based films were characterized by the texture analyzer and the VOC detector. Bananas were used as the climacteric fruit samples to investigate the effectiveness of the zein films as ethylene scavengers. The ultrasonic treated zein film and banana samples were placed in the same plastic sealing bag and then stored at room temperature for 10 d. The performance for extending shelf life was evaluating by browning rate, the flesh hardness, and the weight loss rate of bananas. 【Result】 The HIU treatment (20 kHz, 400 W, 15 min) could effectively stretch the structure of zein. The particle size of the zein and the content of the α-helix were decreased to 1 013.3±6.9 nm, and 45.86%, respectively, and the content of the β-sheet increased to 12.20%. Compared with the zein-0 film, the ethylene adsorption capacity and oxygen resistance of the zein-15 film were increased by 9.486 mg·m-3·h-1 and 0.75×10-16 kg·m·m-2·s-1·Pa-1, respectively. The results including the browning rate, the flesh hardness, and the weight loss rate of bananas indicated that the zein-15 film could effectively extend the shelf-life of bananas. 【Conclusion】 The HIU treatment (20 kHz, 400 W, 15 min) could effectively induce to stretch the zein structure and expose more functional groups, resulting in an improved ethylene adsorption performance of zein. The zein-15 film presented a better ethylene adsorption capacity, oxygen permeability, and mechanical property, leading to an extended shelf life of bananas and its life as the ethylene scavenger.

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    Apparent Matrix Effect of Yeast Polysaccharides from S. cerevisiae on the Hydrolysis of Wine Fruity Esters
    KONG CaiLin, XU YinHu, HUANG Jie, FENG Lin, YAN XinYi, TAO YongSheng
    Scientia Agricultura Sinica    2023, 56 (6): 1168-1176.   DOI: 10.3864/j.issn.0578-1752.2023.06.012
    Abstract187)   HTML26)    PDF (722KB)(122)       Save

    【Objective】 The aim of this study was to investigate the apparent matrix effect of yeast polysaccharide (YP) from S. cerevisiae on the hydrolysis of fruity ester, and to explore the potential application of yeast polysaccharide in stabilizing wine aroma profile and expand shelf life of product. 【Method】 YP was extracted from S. cerevisiae by hot water extraction and alkali methods, and the basic components of YP were analyzed by ultraviolet spectrophotometer (UV), gas chromatography (GC) and high- performance liquid chromatography (HPLC). The model wine containing the conventional concentration of fruity esters was prepared and treated with YP, and the concentration of YP was set in the range of 0-2.0 g·L-1. The effect of YP on the volatility of fruity esters was analyzed by the static headspace method. Next, the model wines with different treatments were stored at 4℃ for 6 months, and the content of fruity esters in model wine was regularly monitored. Finally, sensory analysis was used to evaluate the aroma notes of model wine stored 6-months. 【Result】 Instrumental analysis showed that the total polysaccharide content of YP was (72.61±3.29)%, and the protein contents accounts for (11.20±0.02)%. The main monosaccharide composition of YP was mannose and glucose, and their molar ratio was 1.790:1. The high molecular weight components of YP are 18, 163 and 21 819 kD, and the low molecular weight components are 576 Da. Static headspace analysis indicated that YP treatment could reduce the volatility of acetate esters in model wine, especially 0.8 g∙L-1. While YP treatment could increase the volatility of ethyl esters. Data of regular sampling found that the hydrolysis rate of ethyl esters was significantly higher than that of acetate esters during 6 months storage. Compared with the control, 0.4-0.8 g∙L-1 YP slowed down the hydrolysis of acetate esters and ethyl esters by 10%-40% and 3.7%-26.7%, respectively. Sensory analysis showed that model wine added with YP showed higher MF% of temperate sour and sweet fruity, and preserved fruit and floral aroma notes of wine samples compared with the control. 【Conclusion】 From the study of model wine system, it was concluded that adding 0.4-0.8 g∙L-1 YP during wine storage slowed down the hydrolysis of fruity esters, stabilized wine fruity aroma profile, and showed potential application value for prolonging wine shelf life.

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    Lipid-Lowering Effects and Its Regulation Mechanism of Buckwheat Polyphenols in High-Fat Diet-Induced Obese Mice
    YAO YiJun, JU XingRong, WANG LiFeng
    Scientia Agricultura Sinica    2023, 56 (5): 981-994.   DOI: 10.3864/j.issn.0578-1752.2023.05.013
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    【Background】At present, relevant animal experiments have confirmed that buckwheat had a good intervention effect on obesity and lipid metabolism disorder caused by high-fat diet. At the same time, studies have shown that the adaptive thermogenesis of brown fat could effectively improve the body’s energy metabolism. Therefore, increasing the activity of brown fat and promoting the browning of white fat could be used as an effective way to prevent obesity and improve energy metabolism diseases.【Objective】The raw buckwheat and four kinds of main polyphenols identified from buckwheat were prepared according to the content proportion to study the lipid-lowering effects of buckwheat polyphenols in high-fat diet-induced obese mice via browning of white adipocytes.【Method】Phenolic compounds in buckwheat polyphenol extract were identified by UHPLC-Q-Orbitrap mass spectrometry combined with database. And the main polyphenol compound was prepared according to the content proportion in the raw buckwheat. In order to explore the regulating effects of buckwheat on body weight, organ index and blood lipid level in C57BL/6J mice, the dietary intervention was carried out with 10%, 20% and 40% proportion of buckwheat to replace basic feed and the 2.5 mg∙mL-1 of mixture buckwheat polyphenol standard substance. Last but not least, Western-blot and q-PCR were used to investigate the effects of buckwheat feed and polyphenol intervention on the expression of heat-producing proteins and genes in white and brown fat in mouse subcutaneous adipose tissue.【Result】Twenty phenolic compounds in buckwheat polyphenol extract were identified by UHPLC-Q-Orbitrap mass spectrometry, and the content of four phenolic compounds with the highest content (hydroxycinnamic acid, quercetin,scoparone, and rutin) accounted for more than 80% of the total phenolic compounds, which were the main polyphenols in buckwheat. The results showed that after 39 d in the diet intervention, compared with high-fat diet group, adding buckwheat feed and buckwheat polyphenol intervention on body weight in mice, the liver index and serum triglyceride (TG), total cholesterol (T-CHO), low-density lipoprotein cholesterol (LDL-c), aspartate aminotransferase (ALT) and third transaminase (AST) increased significantly inhibitory effect; with the increase of amount of buckwheat, the inhibition increased. At the same time, adding buckwheat feed and buckwheat polyphenol could protect and improve the decrease of renal index and HDL-c in mice. It was also the high dose 40% buckwheat and polyphenol group that had the best effect, which showed that phenolic substances played a major role in the improvement of abnormal lipid metabolism in high-fat diet-induced obese mice. UCP1, PRDM-16, and PGC-1α protein and gene expression levels were significantly decreased in the high-fat diet group compared with the normal diet group, while Tcf21 and HOXC8 expression levels were significantly increased (P<0.05). After dietary intervention, protein expression levels of UCP1, PRDM-16 and PGC-1α in the buckwheat intervention group were significantly up-regulated, while protein expression levels of Tcf21 and HOXC8 were significantly decreased (P<0.05). In addition, the 40% buckwheat and polyphenol intervention group significantly increased the expression of UCP1, PRDM-16 and PGC-1α genes in mouse visceral adipose tissue (P<0.05), and which down-regulated the expressions of Tcf21 and HOXC8 genes.【Conclusion】Buckwheat intervention could effectively improve the lipid metabolism disorder in high-fat diet-induced obese mice, and it was confirmed that buckwheat polyphenols played a major role. The mechanism was mainly buckwheat polyphenols could significantly improve the thermogenic activity of brown fat, reduce the content of white fat, and regulate the energy metabolism balance. This study provided a new idea and theoretical basis for the utilization of buckwheat and the development of functional foods about lipid-lowering products.

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    Effects of Pulsed Electric Field on Gelation Properties of PSE-Like Chicken Myosin: A Molecular Dynamics Simulation Analysis
    GUO YuChen, DONG Ming, ZENG XianMing, TIAN HuiXin, YIN JiaQi, HOU YuKe, BAI Yun, TANG ChangBo, HAN MinYi, XU XingLian
    Scientia Agricultura Sinica    2023, 56 (4): 741-753.   DOI: 10.3864/j.issn.0578-1752.2023.04.012
    Abstract185)   HTML24)    PDF (2666KB)(68)       Save

    【Objective】In the present study, the effects of pulsed electric field (PEF) on pale soft exudative-like (PSE-like) chicken myofibrillar protein gel properties and conformational modification were investigated by molecular dynamics simulation. The potential mechanism of gel properties change was explored, so as to broaden the industrial application of this emerging food processing technology and to provide a novel method for enhancing abnormal meat products economic benefit in poultry processing. 【Method】Myofibrillar protein was extracted from PSE-like chicken. Effect of PEF under 8, 18 and 28 kV·cm-1 electric field intensity (800 Hz, duty cycle 47%) were compared with untreated samples of PSE-like chicken myofibrillar for turbiscan stability index (TSI) and rheological properties, and the PEF simulation system of 18 kV·cm-1 electric field strength was established by molecular dynamics simulation technology. The root mean square deviation (RMSD), root mean square fluctuation (RMSF) and the overall conformational changes of proteins were collected to explore the mechanism of PEF treatment on the molecular conformational changes of myofibrillar proteins in PSE-like chicken, and the effects of PEF on the conformational stability, water holding capacity (WHC) and rheological properties of myofibrillar protein extracted from PSE-like chicken were also evaluated. 【Result】The TSI of the PSE-like chicken myofibrillar protein system treated by PEF with various field strengths had a smaller slope, which indicated that the protein system was more stable than the untreated sample. The results of WHC of protein gel were 18 kV·cm-1 (81.42%)>28 kV·cm-1 (79.46%)>8 kV·cm-1 (77.82%)>0 kV·cm-1 (76.15%). The rheological properties demonstrated that the changes of storage modulus (G') and loss modulus (G") had the same trend as that of WHC, and the treatment of 18 kV·cm-1 significantly improved the G 'and G" of myofibrillar protein gel (P<0.05). The molecular dynamics simulation result of 30 ns under 18 kV·cm-1 PEF revealed the polymer protein model acted higher RMSD value and more obvious RMSF fluctuation after treatment, which reflected that the secondary structure of protein molecule was uncoiled and unfolded, α-helix was transformed into irregular crimp, protein polypeptide chain was expanded, amino acid residues were exposed, and protein molecules displayed higher flexibility. Interactions of protein-protein and protein-water have been modified, such as electrostatic interaction, hydrogen bond, disulfide bond, hydrophobic interaction. However, when the electric field intensity increased to 28 kV·cm-1, myosin aggregated due to the enhancement of protein-protein interaction, which reduced the effect of PEF on protein property. 【Conclusion】The 18 kV·cm-1 PEF changed the inherent spatial structure of PSE-like chicken myofibrillar protein, the exposure of hydrophobic groups and the formation of hydrogen bonds enhanced the binding of protein and water molecules and the interaction between protein molecules, thus improving the stability and rheological properties of PSE-like chicken myosin gel, which contribute to better gel WHC and elastic network structure.

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    Research Progress on the Application of Non-Saccharomyces During Wine Fermentation
    WANG ChunXiao, YU JunZhu, ZHOU WenYa, XU YinHu
    Scientia Agricultura Sinica    2023, 56 (3): 529-548.   DOI: 10.3864/j.issn.0578-1752.2023.03.011
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    Non-Saccharomyces yeast are naturally present on grape skin, which mainly play their roles in the maceration and initial stage of fermentation during winemaking process. More and more concerns have been recently focused on the application of non-Saccharomyces yeast in wine fermentation. Non-Saccharomyces yeast often have weaker fermentation ability than Saccharomyces cerevisiae and can convert the reducing sugar into ethanol and other fermentation by-products. Therefore, non-Saccharomyces are the potential excellent yeast for producing wine with complex flavor traits and lower ethanol degree. Different non-Saccharomyces yeast species have different metabolic characteristics in wine fermentation applications. The selection of non-Saccharomyces yeasts with certain characteristics for application in fermentation can improve the specialized quality of wine. This review was based on the initial summary on the species, winemaking traits, and application ways of commercial non-Saccharomyces yeast, and emphasized on the positive role of non-Saccharomyces in wine color, aroma, taste, safety and health, their metabolic mechanisms and corresponding research hotspot. The positive role of non-Saccharomyces in wine color included the promotion of high acid production, high polysaccharide production, high extracellular pyruvate production and low sorption properties. Different non-Saccharomyces yeast could promote the fruity aroma enhancement in wine by low production of ethanol, acetaldehyde, and volatile phenols, and high production of ethyl acetate, acetic acid ester, ethyl ester, higher alcohols, and enzymes related with the release of terpene and mercaptan, and therefore improve the aroma complexity of wine. Non-Saccharomyces yeast could regulate wine mouthfeel traits by high production of glycerol, polysaccharide, and lactic acid, and degradation of malic acid. In addition, non-Saccharomyces yeast could improve the safety quality of wine by decreasing the SO2 dosage as biological control agent, and reducing the content of toxic compounds through metabolic degradation during alcoholic fermentation. This review further analyzed the current research status on genome and microsatellite loci analysis. The main inoculation strategies were discussed on application of non-Saccharomyces yeast during wine fermentation, and six aspects were posed for further research concern. This review provided theoretical references for the research on application of the non-Saccharomyces yeasts in wine alcoholic fermentation.

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    Inhibition and Interaction of Pleurotus eryngii Polysaccharide and Its Digestion Products on Starch Digestive Enzymes
    XU Qian, WANG Han, MA Sai, HU QiuHui, MA Ning, SU AnXiang, LI Chen, MA GaoXing
    Scientia Agricultura Sinica    2023, 56 (2): 357-367.   DOI: 10.3864/j.issn.0578-1752.2023.02.012
    Abstract271)   HTML37)    PDF (622KB)(93)       Save

    【Objective】In the present study, the investigation on the basic physicochemical properties of Pleurotus eryngii polysaccharide (PEP) and its related effects on diffusion and adsorption of glucose were conducted. PEP mimetic digestion products (D-PEP) were prepared using an in vitro stimulated digestion model to explore the effects of PEP and D-PEP on the digestive enzymes activities associated with glucose metabolism, as well as the interaction between PEP/D-PEP and α-glucosidase. 【Method】Firstly, the basic physicochemical properties of PEP were detected based on the methods in previous studies. Then the inhibitory effects of PEP/D-PEP on α-amylase and α-glucosidase activities were evaluated by DNS method and 4-Nitrophenyl α-D-glucopyranoside (PNPG) method, respectively. Finally, the relationship between PEP/D-PEP and α-glucosidase was studied with the utilization of the fluorescence spectroscopy technique. 【Result】 PEP displayed great potential on the solubility, swelling property, water and oil holding capacities, and favorable inhibition on glucose diffusion and adsorption. Moreover, PEP had obvious inhibitory effects on maltase and α-glucosidase, while it did not suppress the activity of α-amylase. Specifically, PEP with its concentration of 4 mg·mL-1 exhibited (77.20±2.71)% inhibition ratio on maltase activity, while (78.91±0.51)% inhibition ratio on α-glucosidase activity. However, the digestion product D-PEP showed significant inhibition on the activities of all these three enzymes, with 4 mg·mL-1 of D-PEP inhibiting α-amylase, maltase, and α-glucosidase by (84.08±1.79)%, (20.58±1.20)%, and (95.58±0.12)%, respectively. The outcomes of fluorescence spectroscopy showed that the endogenous fluorescence of α-glucosidase was gradually decreased along with the increasing of the PEP/D-PEP concentration, and the quenching of the endogenous fluorescence of α-glucosidase by PEP/D-PEP was mainly static quenching, with the number of binding sites greater than or equal to 1. 【Conclusion】In summary, D-PEP not only inhibited maltase and α-glucosidase activities but also showed great potential inhibition effects on α-amylase activity compared with PEP. Herein, D-PEP displayed stronger inhibitory effect on amylase and could be considered affect glucose metabolism to a certain degree.

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    Quantitative Detection Technology of Porcine-Derived Materials in Meat by Real-time PCR
    ZHAI XiaoHu,LI LingXu,CHEN XiaoZhu,JIANG HuaiDe,HE WeiHua,YAO DaWei
    Scientia Agricultura Sinica    2023, 56 (1): 156-164.   DOI: 10.3864/j.issn.0578-1752.2023.01.012
    Abstract447)   HTML34)    PDF (1687KB)(100)       Save

    【Objective】The aim of this study was to develop a rapid and accurate quantitative method for identifying porcine-derived materials. 【Method】Porcine microsatellites DNA were selected from GenBank nucleotide database. Primers specific for porcine were designed based on the sequences of microsatellite DNA. Genomic DNA from 10 kinds of common animals was amplified by PCR method. The specificity of selected microsatellite DNA to porcine-derived materials was judged by the amplification products. According to the microsatellite sequence, the specific primers and probes were designed to establish a Real-time PCR method for identifying porcine-derived materials. The double standard curve was used to quantify the porcine-derived materials and total animal-derived materials, respectively, and the percentage content of porcine-derived materials was calculated. 【Result】Porcine specific microsatellite DNA with the accession number EF172428 was selected. Only porcine DNA gave a fragment through PCR assay, while there was no amplification for other non-target animal species DNA. The limit of detection was 0.02 ng in a 25 μL reactive system using the Real-time PCR method. This method could accurately detect porcine-derived components in mixed DNA samples and mixed meat samples with 1.32% percent error and 1.06%-7.12% percent error, respectively. 【Conclusion】The quantitative detection method of porcine-derived materials by Real-time PCR in this research could be used to detect the percentage content of porcine-derived materials in mixed samples.

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    Optimization of Drying Process in Oat Noodle Production
    LIU ZhenRong,ZHAO WuQi,HU XinZhong,HE LiuCheng,CHEN YueYuan
    Scientia Agricultura Sinica    2022, 55 (24): 4927-4942.   DOI: 10.3864/j.issn.0578-1752.2022.24.011
    Abstract222)   HTML43)    PDF (2014KB)(68)       Save

    【Objective】 The effects of different drying modes, temperature, and relative humidity on drying quality and drying energy of oat noodles were studied. The modes were established and the multi-objective optimization was carried out to obtain the drying mode and process parameters of oat noodles with good quality and low energy consumption. 【Method】The effects of nine different drying modes of temperature and humidity on the drying quality and drying energy of oat noodles were studied. The factors of optimal cooking time, cooking loss, water absorption, ductility, hardness, chewiness, adhesiveness, bending strength, breaking distance, acidity and fatty acid value were analyzed to obtain the comprehensive evaluation value of quality and determine the optimal drying mode of oat noodle. Plackett-Burman test was used to screen the first temperature, the first relative humidity, the second temperature, the second relative humidity, the third temperature and the third relative humidity of the three-stage drying of oat noodles with variable temperature and humidity. Box-Behnken response surface test was used to optimize the drying process, and the optimal parameters were obtained and verified. 【Result】The best drying mode of oat noodles was first heating and then cooling combined with dehumidification. Plackett-Burman experiment showed that the key factors of drying oat noodles were the first stage relative humidity, the second stage temperature and the second stage relative humidity. The established regression model of oat noodle drying process parameters with unit energy consumption and the comprehensive score was significant (P<0.05). Each factor had extremely significant influence on unit energy consumption. The interaction between the first relative humidity, the second temperature, and the second relative humidity was extremely significant. All factors had a significant influence on the quality comprehensive score, and the order of influence was second-stage temperature>second-stage relative humidity>first relative humidity. The interaction between first relative humidity, first relative humidity and second relative humidity was significant. The optimal process parameters for three-stage variable temperature and humidity drying of oat noodles were first stage temperature of 25℃, first stage relative humidity of 88%, second stage temperature of 43℃, second stage relative humidity of 71%, third stage temperature of 35℃, and third stage relative humidity of 50%; under this condition, the drying energy of oat noodles was 93.42 kJ·g-1, and the comprehensive score was 1.02. 【Conclusion】The established quadratic polynomial regression model could be applied to analyze and predict the effects of drying process parameters on drying energy and the comprehensive score of oat noodles. Three-stage variable temperature and humidity drying could improve the drying quality of oat noodles and reduce energy consumption. The method of using experiment design and data processing technology to solve the drying process of oat noodles was comprehensive and efficient. The results were intuitive and accurate, and the experiment efficiency and accuracy were improved. This study provided a theoretical basis for industrial standard production, energy-saving, and consumption reduction of oat noodles.

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    Physiological Metabolic Rol e of Nanocomposite Packaged Agaricus bisporus During Postharvest Cold Storage Analyzed by TMT-Based Quantitative Proteomics
    WANG Chao,FANG DongLu,ZHANG PanRong,JIANG Wen,PEI Fei,HU QiuHui,MA Ning
    Scientia Agricultura Sinica    2022, 55 (23): 4728-4742.   DOI: 10.3864/j.issn.0578-1752.2022.23.013
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    【Background】 Agaricus bisporus (A. bisporus) is prone to quality deterioration, such as umbrella opening, water loss, and browning after harvest, which seriously affects the storage quality and commercial value. Our previous research has confirmed that the nanocomposite packaging material (Nano-PM) could effectively delay the postharvest quality deterioration of A. bisporus, but the preservation mechanism is still unclear. 【Objective】 In this study, the differentially expressed proteins of A. bisporus in Nano-PM and polyethylene packaging material (Normal-PM) during storage were analyzed by Tandem Mass Tag (TMT) quantitative proteomics technology. The preservation mechanism of Nano-PM on A. bisporus was further explored. 【Method】 A. bisporus was taken as the research object. The Nano-PM was used for the preservation of A. bisporus, and the Normal-PM was used as the control. The protein extraction and trypsin hydrolysis were performed on A. bisporus during storage. The differentially expressed proteins were screened by TMT labeling and liquid chromatography-tandem mass spectrometry detection. Combined with bioinformatics analysis, the main metabolic pathways involved in differential proteins were studied. Quantitative real-time polymerase chain reaction (qPCR) technology was used to determine the gene expression levels of differential proteins..【Result】 The Nano-PM effectively maintained the appearance quality of A. bisporus and delayed the increase of cell membrane permeability. The number of differential proteins in two groups increased during storage. In the middle (6 d) and late (10 d) stages of storage, the numbers of differential proteins were 62 and 148, respectively. Among them, 22 differential proteins were common. Combined with bioinformatics analysis, these differential proteins were mainly related to pathways, such as energy metabolism and lipid metabolism. The lipid metabolism pathway was mainly analyzed, and the results showed that the Nano-PM had a regulatory effect on the membrane lipid metabolism of A. bisporus. Compared with the Normal-PM, the protein expression of fatty acid synthase, phosphorylcholine cytidylyltransferase, and phosphatidic acid phosphatase under Nano-PM were up-regulated, while the protein expression of key enzymes in membrane lipid degradation, such as phospholipase D and lipase, were down-regulated. At the gene level, the expression of genes encoding these proteins were consistent with the proteomics results..【Conclusion】 The differential proteins of different packaged A. bisporus during storage could be screened and analyzed by TMT-based quantitative proteomics technology. Nano-PM regulated the membrane lipid metabolism of A. bisporus, and inhibited the expression of membrane lipid degradation-related enzymes, which effectively delayed the increase in cell membrane permeability of A. bisporus, maintained the structure and function of the cell membrane, and delayed the quality deterioration of A. bisporus during storage.

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    Differentiation of Porcine Muscle Stem Cells in Three-Dimensional Hydrogels
    CHEN Yu,ZHU HaoZhe,CHEN YiChun,LIU Zheng,DING Xi,GUO Yun,DING ShiJie,ZHOU GuangHong
    Scientia Agricultura Sinica    2022, 55 (22): 4500-4512.   DOI: 10.3864/j.issn.0578-1752.2022.22.014
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    【Objective】 The objective of this study was to explore the differentiation effect of porcine muscle stem cells in three-dimensional hydrogels, and to provide a guidance for inducing muscle stem cells to differentiate into muscle tissue in vitro.【Method】 Some porcine muscle stem cells were respectively induced to differentiate under the conditions of 2D and 3D (2D condition means culturing cells in culture dishes; 3D condition means culturing cells in hydrogels). The RNA and protein samples of porcine muscle stem cells cultured in 2D were collected at proliferation, pre-differentiation, early differentiation, mature differentiation, and late differentiation, respectively, and those in 3D were also collected at day 7 and day 14 of differentiation, respectively. Then, RT-qPCR was used to compare the expression levels of the myogenic-related genes, including the genes of MYOG, CAV-3, MyHC-slow, and MyHC-2a, under 2D and 3D differentiation conditions. Correspondingly, the Western Blot was used to detect the expression levels of MyHC protein and MYOG protein in the two conditions. Moreover, the immunofluorescence staining was used to observe the myotubes formed in cell culture dishes and hydrogels. Further, the amino acid content and composition of the cultured muscle tissue were analyzed by an amino acid automatic analyzer at day 14 of differentiation. 【Result】 The porcine muscle stem cells started to fuse to form myotubes at day 3 of differentiation in 2D. The myotubes formed in 2D matured at day 7 and divorced from culture dish afterwards. The porcine muscle stem cells were still globe and had low expression of MYOG and CAV-3 at day 7 of differentiation in 3D. Multinucleated myotubes formed at day 14 and the expression of MYOG and CAV-3 reached levels of 2D differentiation. The cells in hydrogels had higher expression of terminal differentiation genes MyHC-slow and MyHC-2a than the cells in culture dishes. The expression of MyHC-slow was 12 times that at day 7 in 2D and the expression of MyHC-2a was 4 times that at day7 in 2D, but the expression of MyHC protein was only 1/6 that at day 7 in 2D. Amino acid analysis results showed that the contents of 17 hydrolyzed amino acids in cultured muscle tissue were all lower than those in pork, and the ratio of essential amino acids was also lower in cultured muscle tissue, but the ratio of flavor amino acids was higher. 【Conclusion】 The porcine muscle stem cells could differentiate into myotubes in 3D collagen hydrogels in vitro, and the 3D condition was positive to the expression of myogenic differentiation related genes, but further research was needed to achieve high expression of MyHC protein. The flavor amino acid content of the muscle tissue cultured in this way was high, which might mean good flavor.

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    Characterization of Chilled Mutton by ATP from Different Sources
    SU YuanYuan,ZHANG DeQuan,GU MingHui,ZHANG ChunJuan,LI ShaoBo,ZHENG XiaoChun,CHEN Li
    Scientia Agricultura Sinica    2022, 55 (19): 3841-3853.   DOI: 10.3864/j.issn.0578-1752.2022.19.013
    Abstract242)   HTML35)    PDF (679KB)(84)       Save

    【Objective】 In order to explore a new method for predicting the freshness of chilled mutton, the changes of adenosine triphosphate (ATP in meat, microbial ATP and ATP of meat surface) from different sources during storage were systematically studied, then the ATP that could characterize the change of chilled mutton was screened, and finally the prediction models for the total viable counts and volatile base nitrogen were established. 【Method】 The longissimus dorsi muscle of Small Tailed Han sheep was stored in air sealed packaging at 0℃ for 0, 1, 3, 5, 7, 9, 11, 13, 15, 17, and 21 days, respectively. The freshness indexes (pH, color, volatile base nitrogen, and total viable counts) and ATP from three sources (ATP in meat, microbial ATP, and ATP of meat surface) of chilled mutton were analyzed during storage. The changes of ATP from different sources were evaluated, and the predictive models of freshness indicators were built. 【Result】 The freshness index of total viable counts and volatile base nitrogen in chilled mutton showed an upward trend during storage, and both of them exceeded the national standard limit after 17 days; the ATP in meat showed a decreasing trend, while the microbial ATP and the ATP of meat surface were increased, which was consistent with the change trend of the freshness index; the correlation coefficients (R) between ATP in meat, microbial ATP, ATP of meat surface and total viable counts, total volatile base nitrogen were -0.399, 0.910, 0.943 and -0.357, 0.725, 0.907, respectively. The optimal model for predicting the total viable counts in chilled mutton by ATP of meat surface was Boltzmann, which the formula was TVC (lg cfu/g)=7.649-4.069/(1+exp(x-5.807)/0.632), (R2 =0.903, P<0.001); the optimal model for predicting total volatile base nitrogen in chilled mutton by ATP of meat surface was Expedc1, which the formula was TVB-N (mg/100 g)=2.493*exp(x/3.745)+ 3.057 (R2=0.888, P<0.001). 【Conclusion】 The results showed that the ATP of meat surface of chilled mutton had the significant positive correlations with the total viable counts and volatile basic nitrogen, and then confirmed that the ATP of meat surface could be used as an indicator to characterize the freshness of chilled mutton. The optimal prediction model of the total viable counts and volatile base nitrogen could provide a new idea for rapid detection of chilled mutton freshness.

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    Eating Quality Evaluation of Lamb in Different Postmortem Phases Based on Consumers’ Sensory Preferences
    Yue GE,DeQuan ZHANG,ShaoBo LI,Li CHEN,XiaoChun ZHENG,Ce LIANG,TongJing YAN,JinHuo LI,ZhenYu WANG
    Scientia Agricultura Sinica    2022, 55 (18): 3640-3651.   DOI: 10.3864/j.issn.0578-1752.2022.18.013
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    【Objective】The eating quality of lamb in pre-rigor, rigor mortis and post-rigor phases was investigated by using consumers’ sensory evaluation to understand the differences of eating quality characteristics of lamb in different postmortem phases under instant boiling, roasting, boiling and stir-frying conditions, which was expected to provide the reference for lamb quality evaluation and high-quality meat production.【Method】The oyster cut, short loin, knuckle and silverside in per-rigor, rigor mortis and post-rigor phases were obtained from small-tail Han sheep (male, 8 months old). The sensory attributes (including tenderness, juiciness, flavor and overall liking) of lamb after instant boiling, roasting, boiling and stir-frying were evaluated by consumers. The MQ4 (Meat Quality, 4 variables) equation and the grades boundaries were determined by linear discriminant analysis, which were used to analyze the preference score and eating quality grade of lamb.【Result】After instant boiling, the short loin and silverside in pre-rigor had higher tenderness, flavor and MQ4 scores than those in rigor mortis and post-rigor phases (P<0.05), while there was no significant difference in consumers’ scores of oyster cut and knuckle in different postmortem phases (P>0.05). After roasting, the oyster cut in per-rigor and the silverside in post-rigor phase had higher tenderness, juiciness, overall liking and MQ4 scores than those in rigor mortis (P<0.05), but there was no significant difference in consumers’ scores of short loin and knuckle in different postmortem phases (P>0.05). After boiling, the juiciness and overall liking scores of knuckle in post-rigor were higher than those in per-rigor and rigor mortis phases (P<0.05), and there was no significant difference in consumers’ scores of oyster cut, short loin and silverside in different postmortem phases (P>0.05). After stir-frying, the tenderness, overall liking and MQ4 scores of oyster cut in pre-rigor and post-rigor were higher than those in rigor mortis, while the tenderness, flavor, overall liking and MQ4 scores of short loin in pre-rigor were higher than those in rigor mortis and post-rigor (P<0.05). There was no significant difference in consumers’ scores of knuckle and silverside in different postmortem phases (P>0.05). The premium quality (4star) and good quality (5star) samples were higher in pre-rigor (5star: 0%-8.33%; 4star: 47.83%-72.22%) and post-rigor (5star: 0%-8.70%: 4star: 52.78%-58.33%). There were no unsatisfactory quality (2star) samples in pre-rigor and post-rigor phases, while 4.17% and 4.35% of the samples in rigor mortis were 2star after roasting and boiling, respectively. 【Conclusion】In general, the pre-rigor and post-rigor lamb had a superior eating quality to rigor mortis lamb based on consumers’ sensory evaluation, and the pre-rigor and post-rigor lamb were preferred by Chinese consumers.

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    Research on the Application of a Balanced Sampling-Random Forest Early Warning Model for Aflatoxin Risk in Peanut
    GUO Can,YUE XiaoFeng,BAI YiZhen,ZHANG LiangXiao,ZHANG Qi,LI PeiWu
    Scientia Agricultura Sinica    2022, 55 (17): 3426-3436.   DOI: 10.3864/j.issn.0578-1752.2022.17.013
    Abstract196)   HTML29)    PDF (1182KB)(79)       Save

    【Objective】 Peanuts are highly vulnerable to aflatoxin contamination. Based on the Balanced Sampling-Random Forest early warning model for aflatoxin contamination in peanut established previously, this study aimed to analyze the main technical parameters and practical application effects of the model through systematic application research, which could provide a critical technical support for risk prediction of aflatoxin in post-harvest peanuts in China.【Method】 The model was used to predict the aflatoxin contamination risk of 153 main peanut producing cities in China from 2019 to 2020 by selecting the data of one month before the peanut harvest, including one geographical variable (latitude) and three climatic variables (precipitation, average air pressure, and daily average temperature of 8:00-20:00) as the key input parameters of the model. The immunoaffinity chromatography-high performance liquid chromatography-fluorescence detection method was used to determine the aflatoxin content of 2 164 peanuts to obtain the aflatoxin contamination data areas. The accuracy, precision, sensitivity, and false-positive rate of the model were analyzed to clarify the application effect according to the predicted risk and the actual risk of the model. 【Result】 A total of 125 areas were predicted as low-risk areas of aflatoxin, of which 116 areas were consistent with the actual measurement results, but 9 high-risk producing areas were misjudged as low-risk areas (False negative). Meanwhile, 28 areas were predicted as high-risk areas of aflatoxin, of which 15 areas were consistent with the actual measurement results, but 13 low-risk producing areas were misjudged as high-risk producing areas (False positive). Therefore, the accuracy of the model was 85.61%, the false-negative rate was 8.49%, and the false-positive rate was 5.88%. 【Conclusion】 The application of the Balanced Sampling-Random Forest early warning model could predict the risk of aflatoxin contamination in peanuts, which provided the technical support for scientifically guiding the harvesting, storage and utilization in post-harvest peanuts in China, thereby reducing the loss of aflatoxin contamination and guaranteeing the quality and safety of agricultural products.

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    Flavor Escape Behavior of Stewed Beef with Soy Sauce During Air-Cooling and Refrigeration
    QIANG Yu, JIANG Wei, LIU ChengJiang, HUANG Feng, HAN Dong, ZHANG ChunHui
    Scientia Agricultura Sinica    2022, 55 (16): 3224-3241.   DOI: 10.3864/j.issn.0578-1752.2022.16.013
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    【Objective】This study clarified the escape behavior of key volatile compounds in stewed beef with soy sauce during air-cooling process and refrigeration, aiming to provide the theoretical basis for the flavor preservation and conformity of stewed beef with soy sauce. 【Method】 The volatile flavors in stewed beef with soy sauce were identified by the electronic nose (E-nose) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME/GC-MS) combined with odor activity value (OAV) and principal component analysis (PCA), which defined the dynamic change of flavors during cold air-cooling process (the central temperature was reduced from 50℃ to 10℃, the wind speed was 2 m∙s-1, and the cooling time was 90 minutes) and refrigeration (0, 6, 18, 30, 42 and 54 h at 4℃). Then the escape behavior of key flavor active compounds in stewed beef with soy sauce were revealed. 【Result】According to the E-nose analysis, the flavor profiles of stewed beef with soy sauce exhibited significant differences among the three stages (“out of the pot”, before air-cooling and after air-cooling). Nitrogen oxides, alcohols, aldehydes, ketones, aromatics and organic sulfides were considered the main compounds for the discrepancy. On the other side, the stewed beef with soy sauce after 0, 42 and 54 h refrigeration showed differential flavor profiles, which mainly caused by the variety in nitrogen compounds, alcohols, aldehydes and ketones. However, there was no significant difference in the flavor profiles among 6, 18 and 30 h refrigeration. The HS-SPME-GC-MS results showed that 39, 31 and 33 volatile compounds were identified in three cold air-cooling stages, and the contents were 13 636.18, 9 799.21 and 8 213.86 μg∙kg-1, respectively, with total amounts reducing by 39.8%. Morever, 36, 36, 34, 34, 31 and 29 volatile compounds were identified on different refrigeration periods, the contents were 7 712.65, 6 196.00, 5 319.42, 4 732.69, 5 295.05 and 4 281.82 μg∙kg-1, respectively, and the total contents decreased by 44.5%. Therefore, the flavor escape of stewed beef with soy sauce mainly occurred in the refrigeration stage. Besides, OAV analysis showed stewed beef with soy sauce in the cold air-cooling stage had 18 key active compounds, while eucalyptol, lauryl alcohol, valeraldehyde, and L-carvone were all lost before cold air-cooling, and acetoin, phenethyl alcohol, geranyl acetone, as well as linalool escaped severely, with their OAV values reducing by 81.3%, 64.0%, 63.7% and 55.1%, respectively. 15 key active volatile compounds were identified during refrigeration. Among them, isobutyl acetate and ethyl heptanoate were lost after 6 h. Anethole, eugenol, 4-allylanisole, and linalool were severely escaped, and the OAV values decreased by 63.9%, 63.8%, 58.1% and 53.9%, respectively. Refrigeration was the main stage for the loss and dissipation of flavor compounds in stewed beef with soy sauce; alcohols, ketones, esters and phenolic ethers were more susceptible to lose and escape during air-cooling and refrigeration; the loss and dissipation of flavor compounds were mainly derived from spices. 【Conclusion】This study revealed the escape behavior of flavor active compounds in stewed beef with soy sauce during air-cooling process and refrigeration, and provide the theoretical basis for stewed beef's flavor retention and regulation with soy sauce.

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    Effects of Very Fast Chilling on Flavor Quality in Chilled Lamb
    YAN TongJing,ZHANG DeQuan,LI Xin,LIU Huan,FANG Fei,LIU ShanShan,WANG Su,HOU ChengLi
    Scientia Agricultura Sinica    2022, 55 (15): 3029-3041.   DOI: 10.3864/j.issn.0578-1752.2022.15.013
    Abstract231)   HTML29)    PDF (1555KB)(76)       Save

    【Objective】The objective of this study was to clarify the effect of very fast chilling on flavor quality of chilled lamb, so as to provide a theoretical and experimental basis, to some extent, for developing very fast chilling technology. 【Method】Lamb Silverside muscles were obtained from hot carcasses at 1 h postmortem, and were chilled under conventional chilling (chilling rate 1.94℃∙h-1) and very fast chilling (chilling rate 15.10℃∙h-1), respectively. The contents of nucleotides, free amino acids and volatile compounds were determined during storage. The taste active value and odor activity value were calculated to identify the key volatile compounds in chilled lamb. 【Result】5'-GMP, Alanine and Glutamic acid were identified as the key taste contributors in chilled lamb based on the taste activity value. 13 volatile compounds were identified as key flavor contributors of chilled lamb according to the odor activity value, including 8 aldehydes, 4 alcohols and 1 furan. Specifically, the 8 aldehydes included pentanal, (E)-2-octenal, nonanal, heptanal, (E, E)-2,4-nonadienal, (E)-2-nonenal, octanal, hexanal, the 4 alcohols included hexanol, (E)-2-octene-1-ol, octanol, 1-octen-3-ol, and the furan was 2-pentyl-furan. With the prolongation of storage time, 5'-AMP, 5'-IMP and 5'-GMP were gradually degraded into hypoxanthine and inosine, and sweet amino acids (serine), bitter amino acids (valine, methionine, leucine, tyrosine, phenylalanine, lysine, arginine) and volatile compounds (including 1-octen-3-ol, hexanal, octanal) increased significantly, which changed the flavor quality of chilled lamb in conventional chilling group. The degradation of 5'-AMP, 5'-IMP, 5'-GMP and the formation of free amino acids (including glutamic acid, glycine, proline, valine) and volatile compounds (including 1-octene-3-ol, hexanal, octanal, nonanal, heptanal, hexanol, 2-pentyl-furan) were delayed in very fast chilling group. This change maintained the freshness and reduced negative effects of bitter amino acids, aldehydes and alcohols on the flavor quality of chilled lamb. The result of the cluster analysis showed that flavor quality of chilled lamb at 72 h postmortem in very fast chilling group was similar to that of chilled lamb at 6 h postmortem in conventional chilling group. 【Conclusion】Very fast chilling could delay the changes of volatile compounds and taste compounds, therefore it maintained the flavor quality of chilled lamb in the state of pre-rigor.

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    Effects of Different Drying Methods on Bioactive Components of Shatianyou (Citrus grandis L. Osbeck) Pomace Powder
    LU Qi,JIA XuChao,DENG Mei,ZHANG RuiFen,DONG LiHong,HUANG Fei,CHI JianWei,LIU Lei,ZHANG MingWei
    Scientia Agricultura Sinica    2022, 55 (14): 2825-2836.   DOI: 10.3864/j.issn.0578-1752.2022.14.012
    Abstract201)   HTML27)    PDF (1346KB)(60)       Save

    【Objective】The composition, contents, physicochemical and functional properties of both dietary fiber (DF) and flavonoids of Shatianyou (Citrus grandis L. Osbeck) pomace powder prepared by hot air drying (HAD) and freeze drying (FD) were compared, so as to provide the theoretical basis for the utilization of Shatianyou by-products in the process of functional food. 【Method】Shatianyou pomace powder was prepared by HAD and FD from pomace residues of Shatianyou after the juice was squeezed. The contents of soluble DF (SDF) and insoluble DF (IDF) of Shatianyou pomace powder were determined. The microstructure of the pomace powder was observed by scanning electron microscope and their water retention capacity (WRC), oil adsorption capacity (OAC) and water swelling capacity (WSC) were measured, respectively. The total phenolic and flavonoid contents of Shatianyou pomace powder were measured by Folin-Ciocalteu colorimetric method and Sodium borohydride/chloroquinone assay, respectively. The flavonoids composition of the pomace powder was analyzed by HPLC, and their antioxidant activities were determined by oxygen radical absorbance capacity (ORAC), ABTS radical scavenging capacity and ferric reducing antioxidant power (FRAP) methods. 【Result】The Shatianyou pomace powder prepared by HAD showed higher total DF (46.10 g/100 g DW) content than those obtained by FD (P<0.05); both kinds of pomace powder had balanced ratios of IDF/SDF (1.5 and 1.6, respectively); the WRC (7.55±0.43 g∙g-1 DW) and OAC (1.94±0.08 g∙g-1 DW) of pomace powder obtained by HAD were slightly higher than those obtained by FD, but the later one showed a higher WSC (12.25 mL∙g-1 DW, P<0.05). Phenolics and flavonoids in Shatianyou pomace powder mainly existed in free form, accounting for more than 95% of their total phenolics. The pomace powder obtained by HAD showed significant higher total phenolic contents (5.54 mg GAE∙g-1 DW) than those obtained by FD (P<0.05), but their total flavonoid contents were similar (13.11 and 11.45 mg CE∙g-1 DW, respectively). Naringin and melitidin were the main flavonoids in Shatianyou pomace powder, accounting for more than 70% of their total flavonoids. These were obviously different from those of other citrus fruits, in which naringin was the main flavonoid. Shatianyou pomace powder obtained by HAD, with the ORAC, ABTS and FRAP values of 141.28, 4.63 and 20.98 μmol TE∙g-1 DW, respectively, showed stronger antioxidant activity than those prepared by FD. 【Conclusion】Shatianyou pomace powder was rich in DF and flavonoids, which showed higher hydration properties and antioxidant activities than those of other fruit by-products. Thus, Shatianyou pomace powder was a good source of DF and flavonoid, and could be used in the development of functional food.

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    Preparation, Physicochemical Characterization and Bioactivity Comparison of Different Livestock and Poultry Bone Peptides
    LIU Hong,GUO YuJie,XU Xiong,LI Xia,ZHANG HongRu,QI LiWei,SUN XueMei,ZHANG ChunHui
    Scientia Agricultura Sinica    2022, 55 (13): 2629-2642.   DOI: 10.3864/j.issn.0578-1752.2022.13.012
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    【Objective】The preparation of bone peptides (livestock and poultry bone peptides, LBPs) for the development of bone-derived functional foods is one of the important ways for the high-value utilization of livestock and poultry bone by-products. In this experiment, the leg bone from four main livestock and poultry species were used as raw materials to prepare LBPs based on the same process, and their physicochemical properties and bioactivities were compared and analyzed, so as to provide the reference for the high-value utilization of livestock and poultry bone resources and the development of bone-derived functional foods.【Method】 Yak bone peptides (YBPs), bovine bone peptides (BBPs), porcine bone peptides (PBPs) and chicken bone peptides (CBPs) were prepared from yak, bovine, porcine and chicken leg bones, respectively. Physicochemical properties were characterized, including basic nutritional components, amino acid compositions, molecular weight and particle size distribution. Moreover, the bioactivities of the four LBPs, including osteoblast promoting proliferation, immune regulation, angiotensin converting enzyme inhibitors (ACEI) and antioxidation, were compared and analyzed. 【Result】 The relative contents of crude protein in YBPs, BBPs and PBPs were (89.70±0.77)%, (90.43±0.88)% and (89.36±1.32)%, respectively, which were significant higher than that of CBPs (79.18±1.49)%). The essential amino acids and sulfur-amino acids of CBPs were significant higher than those of YBPs, BBPs and PBPs. The four LBPs were mainly composed of small molecular peptides with MW<2 kD, accounting for about 90%. There was no significant difference in particle size distribution of LBPs powder, which was mainly concentrated in the range of 10-20 µm and 40-60 µm. The bioactivities of different LBPs were analyzed. It was found that YBPs had the most significant osteoblasts promoting proliferation effect, and the proliferation rate was 37.27% at 0.5 mg∙mL-1; BBPs had the strongest effect on macrophage proliferation, and the proliferation rate was 39.26% at 5 mg∙mL-1; PBPs had the strongest ACEI activity, and the inhibition rate of ACE activity was 82.37% at 15 mg∙mL-1; YBPs had the strongest comprehensive antioxidant capacity, compared with BBPs, PBPs and CBPs. 【Conclusion】The physicochemical properties of LBPs from four distinct species were different, but they all met the demand of raw material for the development of bone-derived functional foods. The bioactivities of LBPs from different species were different, which were suitable for the development of different bone-derived functional foods: YBPs had the strongest osteoblasts promoting proliferation effect and comprehensive antioxidant capacity, which was more suitable for the development of bone health improving or antioxidant bone-derived functional foods; BBPs had the strongest effect on promoting macrophage proliferation, which was more suitable for the development of immunomodulatory bone-derived functional foods; PBPs had the strongest ACEI activity and was more suitable for the development of bone-derived functional foods with blood pressure control effect; CBPs had the better powder properties and higher mineral content, which could be used as dietary nutritional supplements.

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    Effects of Thermal Sterilization on Aroma Quality of Flat Peach Juice Based on Sensory Evaluation and GC-MS Combined with OPLS-DA
    TAN FengLing,ZHAN Ping,WANG Peng,TIAN HongLei
    Scientia Agricultura Sinica    2022, 55 (12): 2425-2435.   DOI: 10.3864/j.issn.0578-1752.2022.12.013
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    【Objective】In order to provide a theoretical basis for the quality control of flat peach juice products, the aroma quality changes and the main deterioration factors of flat peach juice after thermal sterilization were investigated.【Method】 Flat peach juice samples were prepared by using four flat peach varieties from Xinjiang province (Zaolupan, ZLP; Zaopan, ZP; Ruipan1, RP1; Ruipan18, RP18) as raw materials and treated at 85℃ for 30 min. Then, the changes of sensory characteristics and aroma composition were investigated by using E-nose, descriptive sensory evaluation (DSA), and GC-MS. Furthermore, OPLS-DA model was applied to screen the marker compounds which caused the quality changes in thermally sterilized juice.【Result】Descriptive sensory analysis and E-nose results indicated that differences existed among four fresh juices, but all of the fresh samples showed high scores in green, peach-like, floral, and fruity attributes. Whereas, the aroma quality of flat peach juice changed greatly after thermal sterilization, as reflected by the decrease of green attribute and the increase of sweet, off-flavor, and cooked flavor. Seven categories of volatile compounds were identified by GC-MS, including esters, lactones, aldehydes, alcohols, ketones, terpenes, and furan compounds. The concentration of aldehydes (hexanal, (E)-2-hexenal), esters (ethyl acetate, hexyl acetate) and terpenes (limonene) decreased significantly after thermal sterilization, while some compounds with off-flavor attribute (pentanal, α-terpineol, β-damascenone) increased significantly. Ten compounds, including three categories compounds (aldehydes, esters, and terpenes) and (E)-2-hexenal, hexanal, ethyl acetate, benzaldehyde, limonene, hexyl acetate and (Z)-3-hexenyl acetate were screened as markers that could distinguish the fresh juice and thermally sterilized juice according to S-Plot and VIP value of OPLS-DA model, so this result verified the accuracy of sensory evaluation and GC-MS analysis.【Conclusion】 The green attribute significantly decreased, meanwhile off-flavor and cooked flavor attributes emerged after thermal sterilization. The decrease of (E)-2-hexenal, hexanal, ethyl acetate, benzaldehyde, limonene, hexyl acetate and (Z)-3-hexenyl acetate and the formation of pentanal and β-damascenone were the main factors for leading to the loss of green attribute and formation of off-flavor and cooked flavor. GC-MS and sensory evaluation coupled with multivariate statistical analysis method (PCA/ OPLS-DA) could be used to accurately evaluate the effect of thermal sterilization on the aroma profile of flat peach juice, and further to trace the key factors of flavor quality deterioration of thermally sterilized juice, which provided a reference for further exploring the degeneration mechanism of thermally processed juice.

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    Effects of Cellulose Replacing Starch on the Gel Properties of Myofibrillar Protein
    WANG LiJian,LUO Cheng,PAN XueFeng,CHEN Xia,CHEN YinJi
    Scientia Agricultura Sinica    2022, 55 (11): 2227-2238.   DOI: 10.3864/j.issn.0578-1752.2022.11.012
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    【Objective】 The effects of replacing starch with cellulose on the gel properties of myofibrillar protein were investigated to provide a theoretical basis for the application of replacing starch with cellulose in sausage.【Method】 Different proportions starch/cellulose-myofibrillar protein were set as the simulation system to study the water holding capacity, color, texture properties, and stress and strain during fracture deformation, to analyze the dynamic rheological properties and creep recovery properties, and to observe the spatial distribution and three-dimensional network structure of starch/cellulose-myofibrillar protein.【Result】 By increasing the proportion of starch and cellulose, the water holding capacity and storage modulus of the composite gel were improved. When the addition proportion of starch and cellulose increased from 0 to 2.0%, the hardness and chewiness of composite gel gradually increased to the maximum; compared with the control group, the hardness was increased by 29.47% and 43.69% respectively, and the chewiness was increased by 34.82% and 41.58%, respectively; however, L* and whiteness had a tendency to decrease. The maximum stress (9 681.86 Pa) and the minimum strain (1.14) were obtained when 2.0% cellulose was added. The value of the creep modulus of the composite gel decreased gradually with the increase of the proportion of starch and cellulose, while the value of the composite gel in the cellulose group decreased more obviously under the same proportion. Paraffin sections showed that starch and cellulose were simply embedded in the gel network structure, but did not cross-link with the protein, and the cellulose formed larger irregular regions in the myofibrillar protein gel system. Based on microstructure analysis, the surface of the control group was rough and there were more cavities. When starch and cellulose were added, the composite gel became uniform and compact, and the cavities were reduced. The protein network structure of cellulose group had better uniformity and compactness under the same addition ratio.【Conclusion】 The addition of starch and cellulose to myofibrillar protein could improve the water holding capacity, color, texture properties, stress and strain during fracture deformation, rheological properties and microstructure of the composite gel, but cellulose had a more significant improvement effect on the composite gel. Therefore, the application of cellulose as starch substitutes in gelatinous sausage was feasible.

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