Physiochemical Indexes And Colour Changes During The Fermentation Process Of Purple Sweet Potato Wine

Purple sweet potato (Ipomoea batatas), is a Convolvulaceae annual herb, containing a large number of anthocyanins. The present thesis focused on quality indicators and colour changes of purple sweet potato wine during fermentation process with mixed microbial and analyzed quality and safety indicators of purple sweet potato wine finished product. The results are as follows:1. Physiochemical Indexes and color changes during fermentation process of purple sweet potato wine were studied. Reducing sugar was going down quickly at 6 d below 4 g/L; while alcohol degree increased, and later the rate of increase was slow and tended to balance. The pH value went down was smallest at the forth day, then going up; The total acid kept increasing and was stable at last. The volatile acid content gradually increased, but totally controlled in less than 1 g/L. Anthocyanin content decreased during the fermentation, which positively correlated with color depth. Purple sweet potato wine fermented by mixed microbial enhanced red tone a*. The chroma C* and H° changed wavely during the fermentation.2. Changes of the pigment components in the purple sweet potato wine production process. Selected key technical points of the fermentation process and dynamic analysised of the type of anthocyanins in purple sweet potato wine with UPLC-ESI-MS/MS methods. The results indicated that 17 kinds of anthocyanin pigments were identified in fresh purple sweet potatoes, which were as follows: cyanidin-3-glucoside,cyanidin-3-sophoroside-5-glucoside, peonidin-3-sophoroside-5-glucoside,cyanidin-3-p-hydroxybenzoylsophoroside-5-glucoside,peonidin-3-p-hydro-xybenzoylsophoroside-5-glucoside, cyanidin-3-feruloylrutinoside-5-glucoside, et al. Cyanidin-3-sophoroside-5-glucoside, cyanidin-3-feruloylrutinoside-5-glucoside was not detected in cooked purple sweet potatoes because of high temperature intolerance. There was no variation of anthocyanin pieces in purple sweet potato wine compared with cooked purple sweet potatoes.3. This experiment determined sensory indicators, physical and chemical indicators, microbial indicators of purple sweet potato wine, including Security indicators such as the content of methanol, ethyl carbamate,et al. The appearance of purple sweet potato wine was bright purple and shiny, clear and transparent, uniform, no precipitation. The typical aroma of the wine is fermented purple sweet potato, sweet and sour taste suitable for delicate and mellow, pure taste. Residual sugar content of purple sweet potato wine was less than 4 g/L, and the alcohol content was up to 13.1%, while acid 4.2 g/L, volatile acid 0.51 g/L, dry extract 21.2 g/L, anthocyanin content 52.54 μg/mL, pH close to 4. The total number of bacteria (CFU/mL)≤50, coliform group (MPN/100mL)<3, and pathogenic bacteria were not detected. The methanol content of the wine was 14.815 mg/L by GC. The ethyl carbamate content of the wine was 155.52 μg/L by GC-MS.