Study On The Browning And Control In The Brewing Process Of Chinese Wolfberry Wine

Wolfberry wine is a kind of health-care fruit wine fermented by yeast.It is rich in nutrients and is popular among consumers.However,wolfberry wine is prone to browning,which not only affects its color and flavor,but also reduces its nutritional value and restricts the development of the wolfberny wine industry.In this paper,the browning problem during the brewing proeess of wolfberry wine was studied.The main factors causing browning and the compound inhibitors controlling browning of wolfberry wine were studied.The main research contents were as follows:(1)Browning in the process of alcohol fermentationThe experiment determined the changes of polyphenol oxidase(PPO)and peroxidase(POD)activities during the fermentation of wolfberry wine,as well as the total phenolic,total flavones,10 phenolic compounds,Vc and Maillard intermediate product 5-hydroxymethyl furfural(5-HMF).It was found that enzymatic browning and non-enzymatic browning occured simultaneously during fermentation.Phenolic compounds were involved in both enzymatic and non-enzymatic browning reactions,which were the main causes of browning.Among them,rutin,chlorogenic acid,ferulic acid,p-hydroxybenzoic acid and p-coumaric acid were more abundant in the fermentation liquid,which had a greater influence on the browning degree.At the same time,the oxidative degradation of Vc and the Maillard reaction of sugars and amino acids were also involved in browning.(2)Browning in the process of wolfberry wine agingThe browning of wolfberry wine in the aging process was a continuation of the browiing factors in the fermentation process,but the enzymatic browning had less influence.The experiment was carried out to determine the changes of total phenolic,total flavones and 10 phenolic compounds,amino acids,total sugars,reducing sugars,Vc and 5-HMF in different aging stages.It was found that phenolic compounds were continuously oxidized and condensed to produce browning substances.Part of the sugars in the total sugars was converted into reducing sugars to participate in the maillard reaction.Using the path analysis,the total phenolic(X1O and total sugars(X2)were independent variables,and the browning degree(Y)was the dependent variable.The optimal regression equation was established:Y=5.809-0.853X1-0.667X2,the independent variables that affected browning degree were considered comprehensively.The direct path coefficients of total phenolic and total sugars on the browning degree of wolfberry wine were-0.682 and-0.345,it was concluded that total phenolic had a greater browning effect on wolfberry wine than total sugars.Through farther simulation experiments,it was concluded that rutin and chlorogenic acid had a greater effect on browning during aging,proline was the amino acid that had the most important influence on browning.(3)Study on compound browning inhibitor for wolfberry wineThrough single factor experiments,Four inhibitors,including glutathione,L-cysteine,sodium D-isoascorbate and EDTA-Na2 with better browning inhibition effect were selected for optimal compounding.The optimal formula of compound inhibitor was:glutathione 0.40 g/L,EDTA-Na2 0.61 g/L,D-isoascorbate 1.63 g/L,L-cysteine 0.72 g/L,and its predicted browning inhibition rate was 45.39%.The actual browning inhlbition rate was 46.72%,which was well fitted to the model.