Study On The Process Technics Optimization Of Purple Sweet Potato Wine With Low Methanol Content

In order to develop the application prospect and economic value of purple sweet potato, this paper determined and analyzed part of nutrient composition in different varieties purple sweet potato; Removed pectin and hydrolyzed starch in raw material with enzymatic hydrolysis, developed a new type of purple sweet potato brewed wine with low methanol content, technological conditions in the process of enzymatic hydrolysis were optimized with response surface and orthogonal test; Analyzed effects of different fermentation conditions on the purple sweet potato wine quality and methanol content in the end. results were as follows:(1) Some nutritions in the Japanese purple potato king, chestnuts ipomoea, Yuzi263, Ningzi1like starch, protein, pectin and so on were determined and analyzed, the results show that Japanese purple potato king is more suitable to purple sweet potato wine as raw material because its water (56.94%)and pectin (2.93%)content are lower, starch(5.813g/10g),reducing sugar(3.76%), anthocyanins(268.33mg/kg) content are higher.(2) The pretreatment conditions of raw material before fermentation were investigated. The antioxidative effects of different color fixative were compared; The influences of feed liquid ratio on soluble solids content in pulp and subsequent process were studied; Response surface test was designed through the Minitab software to optimize the parameters of pectinase hydrolysis; the optimized research on liquefaction and saccharification conditions were in progress. Finally determined that Citric acid is used as color fixative, response time is1.5h. Appropriate feed liquid ratio is1:2; pectinase hydrolysis conditions was optimized by response surface and the optimum technology suggested as follows:pulp initial pH3.5, pectinase addition is5u/g, enzymolysis temperature and time are50℃and60min respectively, the pectin content in pulp (DW) which are used for fermentation can be reduced from6.88%to1.2%after dealing with pectinase; Through the orthogonal test,the optimal conditions for liquefaction were determined as pulp initial pH6.0, amylase addition of3u/g,reacting1h under90℃,the soluble solid content of pulp can up to15.5Brix after liquefaction with above conditions; the optimal condition for saccharification are pulp initial pH5.0, glucoamylase addition of400u/g,reacting2h under55℃, the reducing sugar content of pulp can up to9.57%.(3) The effects of fermentation pH, yeast addition and fermentation temperature on the quality of purple sweet potato wine and methanol content were studied through the single factor and orthogonal test, compared affect of methanol content in final product with pectinase treatment or not.the parameters for brewing purple sweet potato wine were optimized as fermentation pH4.0,yeast addition of0.6g/L, fermentation temperature of25℃, the purple sweet potato wine obtained under the above conditions was featured by clear and transparent appearance, glossy, pure aroma, coordinating taste, the whole quality is best and also has the typical style of the purple sweet potato wine, methanol content of wine less than0.1g/L which was significantly lower than that of potato alcohol(1.2g/L),fruit alcohol(0.4g/L) in the national standard and the wine without pectinase treatment(0.34g/L).