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Present Situation and Prospect of Potato Processing in China     MU Tai-hua, CHEN Jing-wang Scientia Agricultura Sinica   2016,49(9 ):1744 -1745. DOI:10.3864/j.issn.0578-1752.2016.09.010 Abstract  （631） HTML （21） PDF（pc） （222KB）（1452） Save Reference丨 Related Articles丨 Metrics

Domestic and Abroad Research Progress of Potato Tuber-Specific Storage Protein Patatin     ZHANG Du-qin, MU Tai-hua, SUN Hong-nan Scientia Agricultura Sinica   2016,49(9 ):1746 -1756. DOI:10.3864/j.issn.0578-1752.2016.09.011 Abstract  （558） HTML （12） PDF（pc） （446KB）（648） Save Potatoes are the fourth main crops after wheat, rice, and corn. China is the world’s largest potato production country. Along with the development of the potato processing industry, studies on potatoes are going on gradually. Patatin is the potato tuber-specific storage protein, as well as the main part of the potato protein. In addition to its Lipid acyl hydrolase (LAH) and antioxidant activity, Patatin has excellent physico-chemical and functional properties such as solubility, emulsifying, foaming, and gelling properties, and is one of the most popular vegetable proteins. However, no overviews about the physico-chemical properties, the isolation, extraction and purification methods, the application in the food industry, and the future research hotspots of patatin were found up to now. In this paper, the molecular weight, structural characteristics, and physico-chemical properties of patatin were introduced, the method of isolation, extraction, and purification methods of patatin were summarized, and the advantages and disadvantages of each method were compared in order to provide a theoretical reference for the further application, research, and exploitation of patatin in the food industry. The content of patatin in potato protein ranged from 5.4% to 38.0%, relating to the cultivars and metabolic physiology of potato. The molecular weight of patatin varied from 39 kDa to 45 kDa, depending on the degree of glycosylation. Patatin is a kind of globulin with compact structure, and the primary structure contains more than 360 amino acid residues and remained unaffected by the surrounding elements, while the advanced structures were affected by temperature, pH, and so on. Patatin has excellent physico-chemical and functional properties such as solubility, emulsifying, foaming, and gelling properties, which were affected by surrounding elements. Gel chromatography and ion-exchange chromatography are the most common methods to isolate and purify patatin from potato protein, the reversed-phase chromatography (RPC), immunoaffinity chromatography, and gene expression can produce highly purified patatin. Although not suitable for large-scale production, expanded bed adsorption (EBA) chromatography can prepare large amount of patatin with low purity. Research studies on the application of patatin in the food industry are scarce. Patatin has great potential as food ingredients in the food industry, further research studies on Patatin will continue progress toward simplifying extraction methods, cutting the extraction cost, and developing foods, health products, and drugs with high-functional value. Reference丨 Related Articles丨 Metrics

Establishment of a Viscosity Reduction Process by Enzymatic Pretreatment and Its Application in Ethanol Fermentation from Fresh Sweet Potato Without Adding Water     YUE Rui-xue, NIU Fu-xiang, SUN Jian, XU Fei, WANG Hong-yun, ZHU Hong, ZHANG Yi Scientia Agricultura Sinica   2016,49(9 ):1757 -1766. DOI:10.3864/j.issn.0578-1752.2016.09.012 Abstract  （358） HTML （8） PDF（pc） （404KB）（296） Save 【Objective】 The objective of this research was to establish a viscosity reduction process for fresh sweet potato (FSP) mash by enzymatic pretreatment before liquification and use it for direct ethanol fermentation from FSP without adding additional water. 【Method】 A total of 12 kinds of starch-type sweet potatoes (SP), widely cultured in China, were selected for this research. The main components of SP, such as dry matter, starch, protein, soluble sugars, pectin, hemicellulose, cellulose, and lignin, were detected and the correlation between these components and viscosity of FSP were analyzed. Based on the results, proper enzymes, cellulase and pectinase, were selected for viscosity reduction. Effects of some key factors of enzymatic pretreatment on viscosity reduction were investigated, including the ratio of substrate to water (1:0, 2:1, 3:2, 5:4, and 1:1), enzymatic pretreatment time (1, 2, 3, 4, and 5 h), enzymes doses (cellulase: 1.0, 1.5, 2.0, 2.5, and 3.0 GCU·g-1 and pectinase: 1.0, 1.5, 2.0, 2.5, and 3.0 U·g-1), and enzymatic pretreatment temperatures (30℃, 40℃, 50℃, 60℃, and 70℃). The optimum enzymatic pretreatment conditions were determined by orthogonal experiment design and the effects of enzymatic pretreatment on the following ethanol fermentation performance from FSP were also investigated. 【Result】 For 12 kinds of tested starch-type sweet potato varieties, except for hemicellulose (r=-0.239) and lignin (r=-0.069), all the components were positively correlated to the viscosity (dry matter content, r=0.356; starch, r=0.211, soluble sugar, r=0.307; protein, r=0.266; pectin, r=0.526; cellulose, r=0.600). Wherein the pectin (P＜0.01) and cellulose (P＜0.05) were significantly positively correlated to the viscosity. According to the range analysis, the factors affecting enzymatic treatment effects from high to low were enzyme dosage, the ratio of substrate to water, enzymatic treatment time, and temperature. Based on the experiment results and the consideration on the industrial application, the optimum enzymatic pretreatment conditions were determined as: the ratio of substrate to water 1﹕0, cellulase 1.5 GCU·g-1, pectinase 1.5 U·g-1, and 50℃ for 3 h. Besides Wansu 178, mash viscosity from other varieties after enzyme treatment was lower than 3 000 cp, and the viscosity reduction rate was 95.07%-99.31%. At the end of fermentation, the ethanol concentration from 11 kinds of SP varieties was higher than 12% (v/v), and the fermentation efficiency of 9 varieties reached more than 90%. 【Conclusion】 Pectin and cellulose are the main factors affecting the viscosity of SP mash. Fresh SP mash can be directly used for ethanol fermentation after enzymatic pretreatment without adding water. Reference丨 Related Articles丨 Metrics

Lactic Acid Fermentation by Lactobacillus rhamnosus from Sweet Potato Residue     LIU Yu-ting, WU Ming-yang, JIN Yan-ling, SHEN Wei-liang, FANG Yang, ZHAO Hai Scientia Agricultura Sinica   2016,49(9 ):1767 -1777. DOI:10.3864/j.issn.0578-1752.2016.09.013 Abstract  （448） HTML （7） PDF（pc） （566KB）（565） Save 【Objective】Lactic acid fermentation process by Lactobacillus rhamnosus using sweet potato residue was studied in this paper in order to provide new technical strategy for utilization of sweet potato dregs.【Method】Firstly, the major elements of sweet potato starch residue were measured by elemental analyzer, meanwhile, there were four fermentation groups carried out with four different time points during the logarithmic growth phase of L. rhamnosus which was identified through OD value of bacteria, the optimal seed age was confirmed taking the fermentation efficiency of lactic acid production using liquid glucose culture as index of investigation. Then on this basis, the sweet potato dregs were used by L. rhamnosus through solid state fermentation (SSF) in the following research: firstly, the effects of inoculation amount,temperature, CaCO3 quantity, nitrogen sources on lactic acid production were investigated through single factor experiments. In addition, the effects of nitrogen sources on viable bacteria counts in fermenting mash after fermentation were studied also. Then the optimal combination was established by further orthogonal design.【Result】Element analysis results showed that sweet potato starch residue was full of C and H, with weight percentage content of 40.34% and 6.16%, respectively. The content of N was only 0.32%. Although C was quite rich in sweet potato starch residue, N was deficient comparatively, it was necessary to add N source to promote growth and metabolism of L. rhamnosus furthermore. The growth curve of L. rhamnosus identified by ODvalue showed that the OD value of L. rhamnosus increased rapidly after inoculated for 2 h, which means that the logarithmic growth phase began. The OD value wasn’t change approximately after 8 h, which means that the stationary growth stage began. It was confirmed that the logarithmic growth phase of L. rhamnosus was 2 h to 8 h. The fermentation efficiency was the highest, reached 92.39%, when the seed age got to 4 h, and the content of residual glucose was the lowest, reached 0.59 g·L-1, it was confirmed that the optimal seed age of lactic acid fermentation was 4 h. The results of batch single factor experiment through SSF showed successively: The highest fermentation efficiency of 83.87% reached at 10%. The highest fermentation efficiency of 85.55% reached at 37℃, when CaCO3 quantity ranged from 1% to 7%, the highest fermentation efficiency of 90.24% reached at 5%; the fermentation efficiency of urea group reached 91.01% among 4 kinds of inorganic nitrogen source; when urea quantity ranged from 0.4% to 1.6%, the highest fermentation efficiency of 94.13% reached at 0.8%, the viable bacteria counts were 4.32×108 cfu/g. Based on the results of single factor experiments above, the optimal CaCO3 quantity of 5% was suitable for neutralizing the lactic acid produced by initial sugar in fermentation system of 10%, so it was unnecessary to change the optimal CaCO3 quantity, and it wasn’t investigated in the next orthogonal design. Besides, adding cellulase as investigation factor, designing the orthogonal experiment with four factors and three levels. Then, the fermentation optimum conditions were obtained, which were: the inoculation size 10%, urea amount 0.8%, cellulose amount 0.4%, temperature 35℃, CaCO3 quantity 5%, fermentation efficiency and viable bacteria counts, respectively, reached (96.55±0.866)% and 3.04×108 cfu/g under these conditions. 【Conclusion】A low-cost, simple-process, high-efficiency process condition was established which was not only suitable for lactate industry but also beneficial to sweet potato starch processing farmers. Reference丨 Related Articles丨 Metrics

Effects of NaCl Concentration and pH Value on the Emulsifying Properties of Sweet Potato Peptides     CUI Shan-shan, MU Tai-hua, SUN Hong-nan, ZHANG Miao, CHEN Jing-wang Scientia Agricultura Sinica   2016,49(9 ):1778 -1786. DOI:10.3864/j.issn.0578-1752.2016.09.014 Abstract  （356） HTML （6） PDF（pc） （745KB）（492） Save 【Objective】 The study aims to clear the effects of different NaCl concentrations and pH values on the emulsifying properties of sweet potato peptides and provide a theoretical basis for the application of sweet potato peptides in the food industry. 【Method】Microstructure, average particle size (d4,3), emulsifying activity, emulsifying stability, rheological property of emulsion and hydrophobicity of sweet potato peptides with different NaCl concentrations (0.2, 0.4, 0.6, 0.8 and 1.0 mol·L-1) and different pH values (3, 5, 7 and 9) were measured. 【Result】Compared with the sweet potato peptide emulsion without NaCl, when 0.2 mol·L-1 NaCl was added into the sweet potato peptide emulsion, d4,3 was increased from 54.19 μm to 59.70 μm, the emulsifying activity index was decreased significantly from 86.29 m2·g-1 to 56.35 m2·g-1 (P＜0.05), and the emulsion stability index was decreased from 14.84 min to 13.19 min. However, with the increase of NaCl concentration, the uniformity of sweet potato peptide emulsion was decreased, d4,3 was further increased from 59.70 μm to 69.72 μm, the emulsifying activity was decreased from 56.35 m2·g-1 to 32.32 m2·g-1, emulsifying stability was firstly increased and then decreased, reached a maximum of 15.55 min at 0.04 mol·L-1, the initial apparent viscosity was increased and exhibited shear-thinning phenomenon, and surface hydrophobicity activity was decreased. In addition, with the increase of pH value, the uniformity of emulsion was increased, d4,3 was decreased from 64.45 μm at pH 3 to 51.21 μm at pH 9, the emulsifying activity was increased from 3.99 m2·g-1 at pH 3 to 120.47 m2·g-1 at pH 9, the emulsifying stability was firstly increased and then decreased, reached a maximum of 29.13 min at pH 3, initial apparent viscosity was reduced and exhibited shear-thinning phenomenon, and the activity of surface hydrophobicity was increased. 【Conclusion】 Emulsifying properties of sweet potato peptides are closely related to the NaCl concentration and pH value. Addition of NaCl (≥0.2 mol·L-1) reduced the emulsifying activity and stability of sweet potato peptides, while the increase of pH value could effectively improve the emulsifying activity of sweet potato peptides. Reference丨 Related Articles丨 Metrics

Identification of Purple Sweet Potato Color of Cultivar Ningzi No. 1 by HPLC-QTOF/MS and Its Effect on Preventing Obesity in High-Fat-Diet-Treated Rats     ZHANG Yi, WANG Hong-yun, NIU Fu-xiang, SUN Jian, XU Fei, ZHU Hong, YUE Rui-xue Scientia Agricultura Sinica   2016,49(9 ):1787 -1802. DOI:10.3864/j.issn.0578-1752.2016.09.015 Abstract  （431） HTML （11） PDF（pc） （1719KB）（442） Save 【Objective】Purple sweet potato are the main source for natural antioxidants. This study aims to identify the components of purple sweet potato color of cultivar Ningzi No. 1, and investigate the effectiveness of PSPC for the prevention of obesity and the regulatory mechanism of PSPC in obesity prevention.【Method】 Purple sweet potato color was analyzed using an Agilent 1290 series high-performance liquid chromatography connected to an Accurate-Mass Quadrupole Time-of-Flight/MS (HPLC-QTOF/MS). A pH-differential method was used to determine the total PSPC content. Eight-week-old male Sprague Dawley strain rats were fed on either a normal diet containing 11.4% fat, or a HFD containing 40% fat and intragastrically administered PSPC once a day. Body weights of the rats were measured every week after 6 h of fasting. Activities of serum glucose, triglyceride, and total cholesterol were determined using commercial kits. Serum leptin levels were measured using enzyme-linked immunosorbent assay kits. Expression of leptin and leptin receptor mRNAs in the hypothalamus were detected using Real-time Quantitative PCR. Expression of leptin and its downstream proteins in the hypothalamus were analyzed using Western blotting.【Result】Eleven constituents were separated. Based on previous reports, ten constituents were identified and Peak 1 was newly reported herein. The cyanidin 3-glucoside content of PSPC was 17.4%. After 6 weeks, we first examined the changes in body weight. Our data showed that the effect of middle-dose PSPC (371.6±16.3) g was better than low-dose PSPC (384.0±7.2) g, and the effect of high-dose PSPC (358.2±20.1) g was best. Obesity was prevented and glucose, triglyceride, and total cholesterol induced by the HFD were restored to near-normal levels. Compared with control group rats (2.29±0.28) ng·mL-1, the levels of serum leptin in HFD group rats significantly increased by 65.50%. Compared with HFD group rats (3.79±0.24) ng·mL-1, the levels of serum leptin in low (3.13±0.05) ng·mL-1, middle (2.84±0.12) ng·mL-1, and high-dose (2.64±0.06) ng·mL-1 PSPC group rats were significantly decreased. Both of leptin and leptin receptor mRNAs expression in the hypothalamus was upregulated in the different-dose PSPC group compared with that in the HFD group. High-dose PSPC preserved the leptin signaling capability, leading to a decrease in hypothalamic AMPK α activity.【Conclusion】The anti-obesity effects of high-dose PSPC were mediated via a regulation of leptin/AMPKα signaling in the hypothalamus. Reference丨 Related Articles丨 Metrics