Studies On Screening Of Saccharomyces Cerevisiae And Brewing Technology Of Purple Sweet Potato Wine

Purple sweet potato has been paid increasing attention at home and abroad due to its richness inanthocyanins and potential benefits for human health. In this dissertation, isolation and screening ofyeast strains suitable for fruit wine production was carried out and the physiological properties ofselected yeast strains were investigated. The purple sweet potato wine was produced with the selectedyeast strain. The results and findings were summarized as follows:Eighty-four yeast strains were isolated from the soil in fruit orchard and some fruits surface. Of which,thirty-two Strains which had the capacities of carbon oxide and alcohol production were screened out.And ten of thirty-two strains could ferment to make the fermented, mash strong aroma and good mouthfeeling. Through SO₂ tolerance test, two strains of N-1 and N-2 were obtained. It was found that withinseven fermentation inoculated with N-1 and N-2, 7.5 % and 9.2 % of the alcoholic concentration (v/v)were obtained, respectively and in the malt worts with the alcoholic concentrations of 16% and 19 %(v/v) and 160 mg/L of SO₂, both could ferment, producing CO₂ and strong aroma. Their physiologicalproperties were observed. The results showed that the optimum temperatures for the growth of N-1 andN-2 were 28℃and 32℃, respectively, and the optimum initial pH Value were all 6.0. Under thoseoptimum conditions, the maximum biomass was reached in 21 hour fermentation and the biomass of N-1was obviously higher than that of N-2. Those properties suggested N-1 and N-2 were all adapted to wineproduction.The viscosity of 0.6 PaS, 5 mg/mL of starch and 55 mg/mL of reducing sugars in purple sweet potatomash were reached through consequent treatment with pectinase, amylase and saccharifying enzyme, itwas suitable for yeast fermentation. The optimum fermentation process parameters for purple sweetpotato wine were 40% purple sweet potato mash, inoculation population of N-1 2.0×10⁷, temperature28℃, initial pH value 4.0. Based on the optimum conditions, the highest retention of anthocyanins,lowest content of reducing sugars and maximum alcoholic concentration in purple sweet potato winewere observed. This wine had bright red color, clearness, lower bitter with some characteristics of stickrice wine.