Effect Of Bottling Fermentation And Lees Aging On The Quality Of 'Italian Riesling' Sparkling Wine

Bottling fermentation is a traditional method to produce sparkling wines.In this process,acclimation of yeast is the premise to ensure the completion of second fermentation.Fermentation temperature,yeast strain and inoculation amount are the key factors affecting sparkling wine making,however,aging on lees is the most important progress to improve the final quality of sparkling wines.During aging process,the autolysis of yeast and other spontaneous biochemical reactions will change the chemical composition of sparkling wine,so as to the foaming characteristics and aroma quality.Therefore,study on bottling fermentation and aging on lees is an important approach to improve the quality of domestic sparkling wine.In this study,the optimum acclimation condition were determined by evaluating the performance of yeast acclimated in different conditions,Italian Riesling wine were used as base wine to study the effects of fermentation temperature,yeast strain and inoculation amount to secondary fermentation process and quality of sparkling wines.In addition,the quality of sparkling wines and the relationship between foaming characteristics and some components in wines were analyzed.The main results are as follows:1.In this experiment,oxygen condition,sugar content and nitrogen content in substrate during alcohol acclimation were controlled.Based on the comprehensive evaluation of biomass,capacity of flocculation,autolysis,gas production and tolerance of the activated yeast,the optimum activation condition for EC1118 in sparkling wine yeast were determined as follows:anaerobic,30 g/L sucrose,100 mg/L.?NH₄?₂HPO₄.2.The effects of fermentation temperature,yeast strain and inoculum concentration on bottling fermentation were different.When the temperature was 18?,residual sugar content of sparkling wines was lower than corresponding sample wines fermented at 14?by-0.78².29 g/L,CO₂ pressure was higher by 0.34⁰.91 bar.In particular,there is an significant difference between pressures of sample wines fermented by DV10 at two temperatures?P<0.05?.Besides,The pressure of sparkling wine were increased with the inoculation increase of three strains.3.The foam maximum height?HM?,stability height?HS?and stability time?TS?of spakling wines fermented at 14?were higher than those fermented at 18?.Among them,the HM,HS and TS of wines fermented by DV10 were highest and longest,but it was easier to be influenced by fermentaton temperature.In additons,total phenol content of sample wines fermented at 14?was higher than that at 18?by-0.04⁰.37 g/L,and there was no significant difference in color intensity between them.Among all the sample wines,the difference of the content of alcohol,total acid and volatile acid were nearly not significant.4.Effects of fermentation temperature,yeast strain and inoculation amount on contents and quantity of aroma components of sparkling wines were different.The total content of aroma components in sparkling wines fermented at 14?were higher than that of the corresponding wines at 18?by 112.06-683.09?g/L,especially esters and terpenes.Among them,samples wines fermented by DV10 showed the highest aroma content,and there are also differences among innoculation amounts.But DV10 and QA23 strain produced more undesirable flavor,such as octanoic acid and decanoic acid.Besides,1,2-octanediol,2-nonanone and nonanal were additionally detected from some samples fermented at 14?.5.Multivariate variance analysis showed that aging time,yeast strain and inoculation amount had significant effects on the foaming characteristics of sparkling wines.During bottling fermentation and aging on lees,CO₂ pressures in sample wines decreased at the begining and then increased,foaming capacity and stability were increased.Until 9^thh month,sample wines fermented by QA23 and EC1118?inoculation amount at 3×10⁶ and 5×10⁶cells/mL?had high CO₂ pressures,while wines fermented by DV10 and QA23 had good foaming capacity and foam stability respectively.These were related to the contents of protein,polysaccharide,?-amino acid,total phenol and total flavonoids in wines.Besides,residual sugar decreased gradually,while color intensity,alcohol content,total and volatile acid changed a little during this process.6.Principal component analysis of volatile compounds in sample wines during aging progress showed that 1-octanol,2-hydroxyoctanoic acid and 3-methyl-benzaldehyde were increased,while some esters of fruit flavor,alcohols and octanoic acid of undesirable flavor were decreasd during 3^6thh months.During 6^9thh months,some long-chain fatty acid,carbonyl compounds and?-farnesene recongnised as flower flavor were increased,but isoamyl lactate,butanedioic acid,diethyl,decyl alcohol,?-terpineol and citronellol were decreased.