Study On Co-Fermentation Of Chinese Rice Wine With Pichia Kudriavzevii And Saccharomyces Cerevisiae

In this study,yeasts with strong tolerance and good fermentation performance were screened from 8 strains of Saccharomyces cerevisiaes(SC)and 10 strains of Pichia kudriavzevii(PK),respectively,which were applied in mixed fermented Chinese rice wine.Then the fermentation process was optimized and the effects of simultaneous and sequential inoculation on fermentation were investigated.Finally,the flavor substances and antioxidant activity of the fermented rice wine were analyzed.The specific research content is as follows:(1)18 yeasts were screened,the gas production performance showed that the strains except SC1,PK3 and PK6 had stronger gas production performance.Alcohol and the osmotic pressure tolerance test demonstrated that SC2,SC3 and SC4 can tolerate 16% alcohol and 2.0 mo L/L Na Cl,while PK4,PK5 and PK10 can tolerate 12%alcohol and 1.8 mo L/L Na Cl,they had higher alcohol and osmotic tolerance.Ability to tolerate high sugar concentration and low p H showed that SC2,SC3,PK4 and PK5 can tolerate 60% glucose and p H 1.5.The fermented rice hydrolyzate revealed that strain SC3 and PK4 had strong fermentation capacity,and produced more esters and less higher alcohols.Therefore,SC3 and PK4 not only had high tolerance,but also had good fermentation performance.(2)The liquid fermentation technology of Chinese rice wine was optimized by single factor and orthogonal test based on the total higher alcohol content,and the optimal process conditions were selected as follows: the addition amount of acid protease was 5 U/g,the fermentation temperature was 30 °C,and the ratio of material to water was 1:2(g/m L).At this time,the total higher alcohol content of the fermented wine sample was 403.42 mg/L.(3)To explore the effects of different inoculation methods on Chinese rice wine fermentation,the fermentation of Chinese rice wine was performented with single bacteria,simultaneous and sequential mixed bacteria of SC3 and PK4.The results showed that the fermentation with PK4 had the characteristics of long fermentation period and low alcohol content.The alcohol content of sample(SC3)fermented by SC3 single bacteria was higher,and the total higher alcohol content of SC3 sample was the highest,which was 443.35 mg/L.SC3 and PK4 mixed fermentation with 1:1000(1:1000)and 36 h in advance(S-36 h)had the lowest total amount of higher alcohols,which were 350.48 mg/L and 375.86 mg/L,respectively,while the content of ethyl acetate was higher,which were 77.19 mg/L and 90.35 mg/L,respectively.(4)The main flavor substances in Chinese rice wine were analyzed,it was found that the contents of organic acids in SC3 sample,1:1000 sample and S-36 h sample were measured by high performance liquid chromatography,which were 3.16 g/L,3.67g/L and 3.20 g/L,respectively.The volatile compounds in three wine samples were detected by headspace solid-phase microextraction-gas chromatography-mass spectrometry.There were more alcohols in the SC3 sample.The 1:1000 sample and S-36 h sample were rich in esters,especially ethyl acetate and phenethyl acetate.And ethyl hexanoate and β-damassterone were only detected in S-36 h wine sample.Finally,sensory analysis indicated that S-36 h sample wine had obvious floral and fruity aroma,harmonious taste and its quality was better than other samples.(5)The antioxidant activities of wine samples SC3,1:1000 and S-36 h were compared.The results demonstrated that the total phenolic content of the S-36 h sample was the highest and the reducing power was the strongest;the scavenging ability to DPPH free radicals and hydroxyl radicals were as follows: S-36 h sample > 1:1000sample > SC3 sample;the ability of clearing superoxide anion was: 1:1000 sample >S-36 h sample > SC3 sample.