Influence Of Salt-tolerant Yeast On High-salt Soy Sauce Fermentation

The brewing technology of soy sauce mainly includes high salt liquid-state soy sauce fermentation and low salt solid-state soy sauce fermentation.Compared with the low salt solid-state fermentation,high salt liquid-state soy sauce fermentation has a long fermentiom time and high salt which can inhibit harmful microorganisms,so it can be fermented at room temperature.Usually,beneficial yeasts are added to the fermentation process to enhance the flavor and aroma of soy sauce.However,due to the different nature of various yeasts,adding different yeast and adding different time will have different effects on soy sauce products.In this paper,the different adding time and different combinations of salt tolerant yeast in high-salt liquid state fermentation of soy sauce was studied,in order to obtain the best means of adding yeast and improve the flavor and quality of soy sauce.Based on the laboratory strains,three strains of salt tolerant yeast(yeast ?,yeast ? and yeast ?)were identificaed for species.The results showed that the three kinds of yeast were Zygosaccharomyces rouxii(S1 yeast)and Z.rouxii(S2 yeast),Candida versatilis(C yeast).The basic characteristics of these three yeasts were studied.It was found that S1 yeast and S2 yeast began to enter logarithmic growth phase from tenth hours,and C yeast began to enter logarithmic growth phase from fourth hours.The salt tolerance of the three yeasts was analyzed.The results indicated that the salt tolerance of C yeast was the strongest,followed by S1 yeast and S2 yeast.In high-salt liquid state fermentation of soy sauce,the single and different combinations of yeast fermentation were added at 15th,30th and 45th d,respectively.The fermentation process of soy sauce fermentation group various physicochemical indexes(pH,total acid,amino nitrogen,total nitrogen,reducing sugar and salt index)were tracked and other indexes(soluble saltless solid,ammonium salt,color index,organic acid and flavor substances)were analyzed at the end of fermentation.The results showed that for adding a kind of yeast the best addition time of S1,S2 and C yeast was at 30th,45th and 45th,respectively.For various yeasts added at the same time,the best addition time of S1+S2,S1+C and S2+C was 30th d,30th d and 45th d.For various yeasts added at the different time,the best addition method was to add SI yeast at 30th d and to add S2 yeast and C yeast at 40th d.Compared with all the fermentation groups,it was found that for adding a kind of yeast S2 yeast was added at 45th d,whose the physical and chemical indicators were best and there were more flavor products(72 kinds)at the end of fermentation.For the two kinds of yeast,S2+C were added at 45th d and more flavor substances(74 kinds)was found at the end of fermentation.For the three kinds of yeast,the best adding method was that S1 yeast was added 30th d with S2 and C yeast were added at 45th d,and there were most kinds of flavor substances(78 kinds)at the end of fermentation.