Effect Of Yeast Extract On Fermentation Characteristics Of High-salt Liquid-state Soy Sauce

Soy sauce is a traditional condiment in China and is widely welcomed by consumers all over the world.However,soy sauce fermentation is affected by many factors such as raw materials,production technology and production environment,so it is difficult to ensure the quality stability of each batch of products.As a nutrient rich fermentation promoting factor,yeast extract can not only enhance the flavor attribute of soy sauce,but also maintain the micro ecological steady state in soy sauce system and accelerate the fermentation process.In this paper,five different yeast extracts were used in the high salt dilute fermentation soy sauce process.The addition amount of 1% of the mass of soybean was added at the initial stage of fermentation,that is,after koji and salt water were mixed for 24 hours,to explore the influence of different yeast extracts on the fermentation quality of soy sauce and its potential mechanism.The specific research results are as follows:(1)During soy sauce fermentation,bacterial diversity first increased and then decreased,and clock richness gradually decreased.Tetragenococcus,Lactobacillus,Staphylococcus and Bacillus are the dominant bacteria in soy sauce.The addition of yeast extract can improve the competitive advantage of Lactobacillus.At the end of fermentation,the abundance of Lactobacillus in the control group is 4.18%,while in the samples added with yeast extract,the abundance of Lactobacillus was 18.03-23.78%;(2)Compared with the control group,the content of reducing sugar in soy sauce added with yeast extract remained in the relatively stable range of 2.43-2.83 g/100 m L,and its formation was mainly related to Bacillus;(3)The total acid content of soy sauce added with yeast extract was increased,which was up to 11.76% compared with the control group.The formation of total acid was strongly positive with Tetragenococcus,Staphylococcus and Lactobacillus;(4)The content of amino acid nitrogen in soy sauce added with yeast extract also increased,ranging from 12.24-25.51%.Tetragenococcus,Staphylococcus and Lactobacillus had a strong correlation with amino acid nitrogen;(5)The content of soluble salt free solids in the control group was 14.78 g/100 m L,which was grade I soy sauce(>13.0 g/100 m L).The samples added with yeast extract reached the standard of special soy sauce(>15.0 g/100 m L).Its formation was strongly correlated with Staphylococcus,Enterococcus and Lactobacillus;(6)The addition of yeast extract accelerated the formation of volatile compounds related to amino acid metabolism,carbohydrate metabolism,lipid metabolism and other pathways,especially the malt flavor,caramel flavor and smoke flavor in soy sauce;(7)The addition of yeast extract promoted the accumulation of many amino acids,especially glutamate and aspartic acid,and significantly improved the umami of soy sauce;(8)Yeast extract affects the accumulation of metabolites by interfering with the activities of key metabolic enzymes,including branched chain amino acid transaminase,aromatic amino acid transaminase,alcohol dehydrogenase and triacylglycerol lipase.