JIA-2018-09

2132 WANG Ying et al. Journal of Integrative Agriculture 2018, 17(9): 2126–2136 blackberry wine fermented by both FM-S-115 and Hmp-1 (Table 5). But only 16 kinds of volatile compounds had been simultaneously found in the two samples (Table 5). Compared to the blackberry wine fermented by FM-S-115, the kinds and contents of aldehydes and esters decreased in the blackberry wine fermented by both FM-S-115 and Hmp-1, but those of alcohols increased. In addition, 18 kinds of volatile compounds disappeared in this sample, such as hexanal, 2-furancarb oxaldehyde, hexanoic acid ethyl ester, octanal, 2-octenal, 2-decenal and 2-undecenal, and 14 kinds of peculiar volatile compounds were detected, such as benzothiazole, 2-heptanol, N-acetyl-cytidine, cyclotetrasiloxane octamethyl, and so on. 4. Discussion Microbiological spoilage is a serious problem for the food industry, which degrades food products by producing toxins, irritating odor, and forming pellicle (Farkas et al. 2013; Parlapani et al . 2014, 2015). P . membranifaciens is a kind of pellicle-forming yeast, which can produce ascospores and might cause a serious problem when temperature treatment is carried out in the industrial production of fruit juice and wine (Veiga and Madeira-Lopes 2000). In the present study, P . membranifaciens strain Hmp-1 was first ever isolated from the pellicle of spoilage blackberry wine. The result was similar to that of Díaz et al . (2013) who found that P . membranifaciens remained active during the complete wine fermentation. However, a previous study had indicated that P . membranifaciens was not present during wine fermentation, and it was only found at the early stage of alcoholic fermentation (Combina et al . 2005). These contrary results reported in the literatures might be related to the differences in raw material, brewing environments, and the difference of P . membranifaciens strains. The cell population of Hmp-1 was decreased throughout the fermentation period when Hmp-1 was alone inoculated in blackberry juice. However, when Hmp-1 was jointly inoculated with S . cerevisiae FM-S-115, the viable count of Hmp-1 was decreased within 6 d of incubation, and then a sharp increase was noted from 6th d of incubation. The possible reason for the difference of Hmp-1 growth dynamics was the decline of SO 2 concentration in blackberry juice, but the accurate reasons remained to be found in further research. The SO 2 concentration in wine is depended on carbonyl and keto compounds, which are known to form covalent adducts (sulfonates) with SO 2 . There are many carbonyl and keto compounds (acetaldehyde, pyruvic, α-ketoglutaric, galacturonic acids, and acetoin) in wine which were produced during the brewing of fruit wine. Among them, acetaldehyde was identi ed as the most important SO 2 binder (Jackowetz and Mira de Orduña 2013). Bound forms of SO 2 are thought to have decreased preservative activity compared to free SO 2 (Rankine 1968). Table 3 Effects of sugar in different concentrations on the growth dynamics of Pichia membranifaciens Hmp-1 and Saccharomyces cerevisiae FM-S-115 (Log 10 CFU mL –1 ) during fermentation Fermentation time (d) Stain Sugar concentration (w/v, %) 10 15 20 25 1 FM-S-115 6.57±0.23 a 6.54±0.34 a 6.54±0.61 a 6.38±0.44 b Hmp-1 6.34±0.24 a 6.33±0.34 a 6.25±0.34 a 5.95±0.31b 5 FM-S-115 7.87±0.46 7.81±0.61 7.78±0.17 7.84±0.13 Hmp-1 7.53±0.34 a 7.41±0.15 a 7.44±0.55 a 6.45±0.39 b 10 FM-S-115 7.68±0.09 7.62±0.09 7.51±0.24 7.56±0.48 Hmp-1 7.29±0.45 a 7.35±0.51 a 7.22±0.33 a 6.71±0.23 b Total yeast numbers are expressed as the mean values±SD. Different letters within each row mean significant differences ( P <0.05). –, undetected. Table 4 Effects of temperature on the growth dynamics of Pichia membranifaciens Hmp-1 and Saccharomyces cerevisiae FM-S- 115 (Log 10 CFU mL –1 ) during fermentation Fermentation time (d) Stain Temperature (°C) 15 20 25 30 35 1 FM-S-115 6.08±0.34 b 6.14±0.26 b 6.56±0.34 a 6.55±0.19 a 6.64±0.44 a Hmp-1 6.05±0.27 b 6.08±0.17 b 6.31±0.55 a 6.33±0.34 a 6.43±0.53 a 5 FM-S-115 6.24±0.38 c 6.78±0.15 b 7.82±0.34 a 7.86±0.53 a 7.88±0.62 a Hmp-1 6.21±0.15 c 6.51±0.33 b 7.56±0.54 a 7.53±0.61 a 7.62±0.48 a 10 FM-S-115 6.79±0.61 c 7.34±0.21 b 7.53±0.57 a 7.49±0.19 a 7.11±0.71 b Hmp-1 6.55±0.33 c 7.03±0.54 b 7.33±0.41 a 7.41±0.35 a 7.09±0.66 b Total yeast numbers are expressed as the mean values±SD. Different letters within each rown mean significant differences ( P <0.05). –, undetected.