Study On Fermentation Technology Of Proso Millet Yellow Rice Wine By Liquefying Method

In recent years,the planting area of proso millet has been increasing,and the processing of proso millet rice wine has become the mainstream of related development products.However,the development of proso millet rice wine is restricted by the shortcomings of low utilization rate of millet raw materials,difficulty in filtering mash,serious contamination of bacteria and inconsistent taste of rice wine caused by traditional fermentation.Domestic research reports on the use of liquefaction and enzyme to brew yellow wine from rice have been reported.However,there is little report on the brewing of yellow wine by liquefaction using proso millet as raw material.In this study,the fermentation performance of different yeast strains was studied using proso millet as raw material,and yeast strain with good fermentation performance was screened.Then the effects of different protease treatments on the fermentation performance and quality of yellow wine were studied.Finally,the effects of different ultrasonic-assisted enzymatic hydrolysis methods on the fermentation of rice wine were studied,the optimal ultrasonic treatment methods and protease types were determined,which provided theoretical basis for the industrial production of proso millet rice wine.The main findings of this paper are as follows:（1）To study the fermentation performance of six kinds of laboratory-retained yeast strains,the effects of different yeast strains on free amino acids and volatile flavor substances of rice wine were investigated.The results showed that compared with the other five yeasts,the rice wine yeast 2（S2）fermented rice wine showed the highest CO₂ weight loss（77.8 g/L）,the highest ethanol yield（8.10%）and the lowest reducing sugar content（1.24 mg/mL）,the highest volatile aroma content（8509.32μg/L）,containing 41 kinds of aroma substance.Yellow wine yeast strain 2（S2）is strong in cell growth,and ethanol production,and has a lot of flavouring substances in finished wine.It is the most suitable strain for fermentation of proso millet rice wine in this study.（2）The effects of addingβ-glucanase and different proteases on yeast fermentation performance,rice wine amino acid content and wine flavor were investigated.The results showed that the weight loss of CO₂ treated by Neutrase was the highest（176.4 g/L）and the fermentation rate was the fastest.Novozym37071 treated in theβ-glucanase group had the highest FAN consumption（232 mg/L）and the highest ethanol yield（10.50%）,which improved the fermentation performance of rice wine.In the control group,the total content of free amino acids in Flavourzyme-treated rice wine was the highest（145.34 mg/L）.The addition of Novozym37071 in the control group and theβ-glucanase group produced the highest total volatile aroma components,which were 8875.77μg/L and 8415.61μg/L,respectively.The alcohol content and ester content are higher than other three proteases.The three proteases Flavourzyme,Novozym37071 and Neutrase could improve the fermentation performance and quality of proso millet rice wine.（3）The effects of different ultrasound-assisted enzymatic hydrolysis methods on the fermentation performance,free amino acids and volatile aroma components of proso millet rice wine were investigated.The saccharification experiments of proso millet mash were carried out by enzymatic saccharification,ultrasonic-assisted enzymolysis simultaneous treatment and ultrasonic pretreatment followed by enzymolysis,respectively.The results showed that the contents of soluble solids and FAN in saccharifying mash treated by ultrasonic-assisted enzymolysis simultaneous treatment and ultrasonic pretreatment followed by enzymolysis were higher than those of non-ultrasonic treatment.The fermentation performance of two kinds of ultrasound-assisted enzymatic hydrolysis were compared.The results showed that compared with other treatment groups,the FAN content of treatment by addingβ-glucanase and Flavourzyme was the highest at the end of enzymatic hydrolysis（303.58 mg/L）,and at the end of fermentation,the CO₂ weight loss of treatment by addingβ-glucanase and Flavourzyme was the highest（62.13 g/L）,the FAN consumption was the highest（101.15 mg/L）,the ethanol content was the highest（6.9%）and the total volatile aroma substance content was the highest（7577.86μg/L）.Finally,ultrasonic-assisted enzymolysis simultaneous treatment by addingβ-glucanase and Flavourzyme was suggested to be a better method in proso millet rice wine production.