Study On Fermentation Process Optimization And Fermentation Kinetics Of Mulberry Wine

In this thesis,Mulberries were taken as the research object to study the preparation process conditions of mulberry juice,fermentation process conditions,fermentation kinetic equation and clarification process of mulberry wine.The main research contents and results are as follows:(1)Preparation of mulberry juice.Explores the effect of four single enzyme,pectinase,cellulase,protease and xylanase on mulberry juice yield,and the pectinase and cellulase acted a good promoting role for mulberry juice yield;From single factor test and orthogonal test,the optimum enzymatic hydrolysis process were obtained: the ratio of pectinase and cellulase was 1:1.5,the addition amount was 0.2%,the enzymolysis temperature was 50 ℃ and the enzymolysis time was 2 h;Detected the main nutrients of the mulberry juice obtained from composite enzymatic hydrolysis and direct pressing,the results showed that the complex enzymes can not only improve the mulberry juice yield effectively,meanwhile had a good promoting effect on the dissolution of effective components from the mulberry juice.(2)Optimization of fermentation process of mulberry wine.Through single factor experiment,using sensory score,ethanol volume fraction and residual sugar content as indicators,the optimal levels of the initial sugar content,yeast inoculation and fermentation time were determined during the fermentation process of mulberry wine;Response surface optimization was carried out on the basis of single factor test.The process model equation of mulberry wine was obtained with sensory score as the index:Y=87.56+2.60A+0.75B-0.60C-0.90AC-0.95BC-5.41A2-7.21B2-1.45C2The optimized conditions were adjusted according to production needs and the actual production process,the optimization process was obtained: the initial sugar content was 200 g/L,the inoculated size was 0.3%,and the fermentation temperature was 25℃;Using SPME-GC-MS to analyze the volatile components of mulberry wine,the relative content of each substance was obtained by area normalization method: alcohols(41.87%),esters(30.21%),acids(2.25%),aldehydes(4.41%),ketones(10.76%),phenols,heterocyles and other substances were 7.83%.(3)Fermentation kinetics of mulberry wine.In the brewing experiment of mulberry wine,under the condition of 200 g/L initial sugar content,inoculated 5% activated yeast and cultivated at constant temperature of 28 ℃.After fermentation for 100 h,the ethanol content was 9.01%,the residual sugar content was 3.86 g/L,and the number of yeast was 2.83×108 CFU/m L;The yeast entered the logarithmic growth phase with 8 hours fermentation,and then it entered the stable growth phase after 24 h.The ethanol generated along with the growth of yeast.After fermentation to 72 h,sugar content decreased slowly,ethanol volume fraction was stable and the main fermentation was basically completed.Using Logistic model equations,a kinetic model for bacteria growth,substrate consumption and product generation during the brewing process of mulberry wine was established.The nonlinear regression and variance analysis of the equations were performed by origin9.0,and the R2 of predicted value and actual value were 0.974,0.988 and 0.991 respectively.The results had high fitting degree,suggested that the kinetic model can reflect the dynamic changes of bacterial count,substrate consumption and product generation during the fermentation of mulberry wine.(4)Clarification and quality index establishment of mulberry wine.In the thesis,through the single factor experiment,explored the use ratio and clarification effect of four clarifying agents,gelatin,chitosan,PVPP and bentonita.Made a comprehensive comparison by transmission rate and sensory evaluation,the results showed that the addition of 0.8 g/L chitosan had a better effect on clarification.The electronic nose was used to detect the volatile components from juice and clarify and non-clarify wine,the results were determined by PCA and radar chart analysis.The results showed that the mulberry wine had no significant changes in the flavor whether the clarifier was added or not.According to the loading analysis,aromatic components,nitrogen oxides,inorganic sulfides and ethanol compounds had a greater contribution in mulberry wine.Reference to the standards of NY/T 1508-2017 "Green Food-Fruit Wine",GB 2758-2012 "National Food Safety Standard for Fermented Liquors and Prepared Liquors" and GB/T 15038-2006 "Analytical Methods of Wine and fruit Wine",combined with the actual product,the quality standard of mulberry wine was established.