Preparation And Application Of Soy Sauce Active Dry Yeast

The soy sauce yeast can produce alcohol and esters which are important to the flavor of soy sauce. The soy sauce yeast are salt-tolerant yeasts, including Zygosaccharomyces rouxii (S yeast) and Torulopsis versatilis (T yeast). The soy sauce enterprise add fresh yeast that need low temperature preservation equipment and longer activation before using, which increases the cost of production. The appearance of dry yeast will solve this problem.Trehalose can protect biology when it is in the bad environment, so it is necessary to increase the intracellular content of trehalose before drying. This experiment used salinity stimulus and temperature stimulation to improve trehalose content. The results showed that the trehalose of S yeast and T yeast increased from 7.0% and 7.5% to 8.4% and 9.6% respectively under salinity stimulation and 40℃ heat shock for 30 min, S yeast and T yeast could increase from 8.4% and 9.6% to 10.1% and 10.9% respectively. What’s more, the level of trehalose of the mutant ones(S3-2,T3-5) could increase in salt and heat shock, but the trehalose content in the salt and heat stimulation was obviously lower than the original ones.This work discussed drying conditions. The washing water contained 2% salt, and the ratio of span 60 and polysorbate 80 was 1:1. Through the response surface analysis method to determine the strains drying temperature was 38℃, ultimately moisture content was 8%, and adding content of protective agents was 2.1% of the drying weight of yeast cell, then yeast viable rate could reach to 90%. The rehydration conditions were as follow:re-water temperature was 35; re-water liquid dosage was 20 times of dry yeast; the sugar concentration of re-water liquid was 8%; and re-water time was 60 min.The measurement of fermentation performance of dry yeast was to compare the main physical and chemical indicators (reducing sugar, amino nitrogen, total acid) and flavor substance of soy sauce with fresh yeast and dry yeast. The results showed that the fermentation performance of soy sauce dry yeast was well.