| Rice wine is a traditional brewed wine in China,and it is favored by consumers in its outstanding characteristics such as high nutritional value and good flavor.However,the production of traditional rice wine was precluded by the quality instability of the wheat Qu,which limited the development of the rice wine.In this paper,the strains with excellent fermentation performance were screened from wheat Qu,and rice wine was prepared by multi-strain mixed fermentation.The quality of rice wine was controlled under the condition of original flavor.At the same time,the effects of enzyme preparation on rice wine fermentation,and the effect of enzymatic hydrolysate of rice wine lees into rice mash on rice wine fermentation were studied.The main findings are as follows:Three moulds strains were screened by using transparent zone method,polyacrylamide gel electrophoresis method and testing rice method.The initial identification was Rhizopus chinonsis R01,Aspergillus niger A20,and Mucor pusillus M05 by observation of colony morphology and mycelium morphology.The isolated and purified yeast were tested for ester production experiment,alcohol resistance,high sugar tolerance,fermentation capacity,alcohol production performance and effects of aroma compounds in rice wine produced by yeast strains.Saccharomyces cerevisiae S10 was screened,which had growth uniformity,high physiological patience,rich in ester,and high fermentation capacity,its alcoholic-producing ability was higher than other one.Rice wine was produced by mixed moulds starter fermentation.The influence of mixed moulds starters on enological parameters,free amino acids(FAAs),flavor compounds,and sensory characteristics of rice wine were investigated,respectively.Results indicated that the contents of ethanol,amino acid nitrogen,umami and sweet FAAs in rice wine obtained from rice fermentation using starter of simultaneous inoculation of R.chinonsis R01,A.niger A20,M.pusillus M05 and S.cerevisiae S10(RAM-S)were higher than that of Control one.In addition,flavor compound data revealed that the aroma of rice wine using different starters mainly differed in the amounts of alcohols and esters.Partial least square regression(PLSR)analysis demonstrated RAM-S wine had the best sensory characteristics with higher contents of esters,nitrogen-containing,umami and sweet amino acids.The influences of enzyme preparation on the fermentation progress and flavor compounds of rice wine were investigated,respectively.The results showed that the alcohol content in rice wine was 15%(v/v)by adding α-amylase and glucoamylase.The amino acid nitrogen content in rice wine was 0.43 mg/mL by adding acid protease,which was 14.28% higher than the control it.The fermentation efficiency and contents of alcohol,amino acid nitrogen,and total free amino acid and volatile compounds in rice wine adding three kinds of enzyme preparations were improved and increased;their contents were 49.22,26.59,85.54 and 25.71% higher than the control one,respectively.The effects of pretreatment methods and enzymatic hydrolysis conditions of protease of rice wine lees,the influence of enzymatic hydrolysis conditions of rice wine lees protein and the addition form and amount of enzyme hydrolysates on the fermentation of rice wine were explored.The results showed boiling water bath for 5 min was beneficial to the dissolution of yeast protein and the dissolution rate of yeast protein was increased by 48.21% compared with that of Control.The rice wine lees were hydrolyzed by alkaline protease(1000 U/g)at 50 °C for 2 h with pH 10.0 at the substrate concentration of 6%.Rice wine was produced using protease hydrolysate mixture of lees with the amount of 2.0% as adjuvant together with rice mash.Amino acid nitrogen and free amino acid content in the base liquor were 0.521 g/L and 3.553 g/L,respectively,which were 391.51% and 404.69% higher than those of the control,respectively. |
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