Optimization Of Fermentation Proceess For Purple Sweet Potato Wine And Study On The Stability Of Anthocyanins From Purple Sweet Potato Wine

In this work,the purple sweet potatoes were used as raw material to ferment purple sweet potato wine.Using semi-solid fermentation method,a kind of nutritious purple sweet potato wine was obtained.Screening of yeast strains suitable for purple sweet potato wine and the optimization of saccharification and fermentation conditions were investigated in this experiment.The storage stability of anthocyanins in purple sweet potato wine was also examined.The results and findings were summarized as follows:1.In order to select the fine yeast strain,5 yeast strains were identified by morphology study,fermentation power experiment and ethanol tolerance experiment.The Angel alcohol active yeast for yellow rice wine was chosen as the fine yeast for ferment purple sweet potato wine,because it has regular cell morphology,showed strong fermentation power through the purple sweet potato saccharification liquid medium,and still had fine fermentation stability in high ethanol environment.2.Enzymolysis method was used as the saccharification method.The optimization of saccharification conditions was investigated.Purple sweet potato mash was reached through consequent treatment with a-amylase and glucoamylase.The optimal saccharification process is:liquified for 3.0 h with 0.6%a-amylase at 65? and pH 7.0,saccharified for 1.0 h with 1.2%glucoamylase at 60? and pH 3.5.3.The fermentation conditions were optimized by single factor experiments and orthogonal experiment.The result is:fermented for 7 days with 1.7%Angel alcohol active yeast for yellow rice wine at 22? and pH 3.8.Under this fermentation conditions,the alcoholicity of sample wine was 15.4%vol and the anthocyanin content was 112.73 mg/L.The physiochemical indexes of the purple sweet potato wine were all accord with the standards of traditional yellow rice wine in GB/T 13662-2008.The physicochemical standards for purple sweet potato wine were made.The free amino acids in purple sweet potato wine were determined.Results showed that the purple sweet potato wine contained 19 kinds of free amino acids,the total content of free amino acids was 17.68 mg/100mL.Content of 10 minerals were analyzed,the content of Mg?Ca and Se is higher than the common yellow rice wine.4.The effects of storage temperature,pH and light on the storage stability of anthocyanins in purple sweet potato wine were examined.Results showed that the degradation of anthocyanins during storage followed a first order reaction.Anthocyanins in purple sweet potato wine were stable at 5? and 25?,and easy to degrade at 37?.Anthocyanins in purple sweet potato wine had a higher stability at low pH.At pH 3.5,anthocyanins were most stable.Anthocyanins in purple sweet potato wine were stable in dark,and were significantly decreased in daylight lamp and diffused light during 60 d.Storage in dark or in brown glass bottle can reduce degradation of anthocyanins by diffused light.