Studies On Optimization And Fermentation Characteristics Of Saccharomyces Cerevisiae From Circum-bohai Sea Region

Saccharomyces cerevisiae plays a key role in the quality of wine.In order to screen out high-quality native Saccharomyces cerevisiae,111 strains with typical yeast characteristics were isolated from grape fruits,root soil and home-brewed fermented mash of farmers in four provinces and eight cities of Bohai Rim region.Through the fermentation ability test,endurance test and basic fermentation performance test of 111 isolated strains,three strains of yeast with good comprehensive fermentation performance were screened out,namely JL1,RG4 and RB1.JL1 and RB1began to ferment within 12h,while RG4 began to ferment within 36h.All the three strains could tolerate 16%alcohol and 41?high temperature.In addition,JL1 can tolerate400mg/L SO₂,60%glucose and p H 2.0 acidity.RG4 can withstand 400mg/L of SO₂,50%glucose and p H 2.5;RB1 tolerates 350 mg/L of SO₂,50%glucose,and p H 2.5.In terms of basic fermentation performance,the three strains showed high alcohol yield,high ester yield and low foamability.JL1 is low production hydrogen sulfide,RB1 and RG4 is middle hydrogen sulfide.The three strains of Saccharomyces cerevisae JL1,RG4,RB1 and commercial yeast were separately fermented Cabernet Sauvignon wine at room temperature,and the dynamic indexes of reducing sugar,alcohol content and total acid were monitored.After the fermentation,the reducing sugar of Saccharomyces cerevisae JL1,RG4,RB1 and commercial yeast fermentation broth were all reduced to less than 4 g/L.The alcohol content was 9.8%vol?12%vol.The total acidity of all the wines ranged from 5.5 g/L to 6.0 g/L,which met the fermentation requirements.Combined with sensory evaluation scores and physical and chemical indicators,JL1 was retained as the optimal yeast for subsequent tests.The selected yeast JL1 was identified and classified as Saccharomy cescerevisiae by WL nutrient AGAR medium.The selected native yeast JL1 and commercial yeast RA were used to separate ferment Cabernet sauvignon grapes.After the fermentation,the alcohol content,reducing sugar,total acid,tannin,anthocyanin,total phenols,chroma and tone values,aroma analysis and sensory evaluation were detected in each wine.Results The anthocyanins,total phenols and chroma of JL1 fermented Cabernet Sauvignon wine were higher than those of commercial control bacteria,but the tannin content and sensory evaluation were slightly lower than that of commercial control bacteria,and the sensory evaluation was lower than that of commercial control bacteria.GC-MS method was used to determine the aroma substances in different wines.The results showed that the varieties and quantities of aroma substances in the selected native yeast JL1 fermented Cabernet Sauvignon wine were lower than those in the Cabernet Sauvignon wine fermented by commercial yeast RA.The selected local Saccharomyces cerevisiae and non-Saccharomyces cerevisiae were co-fermented Cabernet Sauvignon grapes at the ratios of 3:7,5:5 and 7:3,respectively,and scored by sensory evaluation.Results The sensory scores of the three wines were all higher than that of JL1 fermented Cabernet Sauvignon alone.Cabernet sauvignon wines mixed with the ratio of 5:5 and 7:3 had higher sensory scores than those fermented by commercial control bacterium RA alone.