Effects Of Salt Content On The Quality And Microbial Communities Of Spontaneous Fermented Toona Sinensis Paocai

Toona sinensis is a kind of woody vegetable with strong aroma and rich in nutrients and functional ingredients.However,toona picking is seasonal,and toona is difficult to keep fresh,which cannot meet the perennial demand of consumers.Fermented foods have a long shelf life and unique flavors,but due to different fermentation conditions,the microbial diversity in fermented vegetables is different,which affects the sensory and nutritional quality of fermented foods.This article analyzes the physical and chemical properties,biological activity and flavor of toona paocai with 4%salt content(TSPC4),toona paocai with 6%salt content(TSPC6),and toona paocai with 8%salt content(TSPC8)during the fermentation process.Evaluate the quality characteristics of Spontaneous fermented toona paocai is expected to provide a basis for enriching the types of toona processed products and the industrialized production of toona fermented foods.The main findings are as follows:(1)TSPC4 has the fastest acid production rate,the largest acid production,and the shortest maturity period.Its color is better than TSPC6 and TSPC8,its total phenol content and antioxidant activity are better than TSPC6 and TSPC8,and the total number of microorganisms and lactic acid bacteria is the highest;salt content It has no obvious effect on the total flavonoid content in TSPC.The nitrite content of mature TSPC is far lower than the national hygiene standard.TSPC has significant antibacterial effects on four common pathogens.TSPC8 has the strongest antibacterial ability against Staphylococcusaureus,Salmonellaenteritidis,and Listeriamomocytogenes;TSPC4 has the best antibacterial ability against Escherichia coli.(2)The content of lactic acid and acetic acid in mature TSPC4 are both the highest.The content of malic acid and ascorbic acid in TSPC is greater than that some common vegetables.Glu is the amino acid with the highest content in TSPC.Compared with other TSPCs,TSPC8 has the highest Glu content;the total amount of amino acids and essential amino acid content of TSPC8 are also higher than TSPC4 and TSPC6.In TSPC,umami amino acids and sweet amino acids contribute more to flavor than bitter amino acids.TSPC8 has the largest variety of volatile flavor substances at maturity,up to 62,and its total amount of volatile compounds is also the highest.The flavor markers of TSPC with different salt content are different,the characteristic volatile compounds of mature TSPC4 are 2-mercapto-3,4-dimethyl-2,3-dihydrothiophene and 2,4-dimethyl-thiophene;the characteristic volatile compounds of TSPC6 are ethyl acetate,1,2-propenyl disulfide,cis-3-hexenol;the characteristic volatile compounds of mature TSPC8 are cubaene,?-pinene,eucalyptol,4-terpene alcohol,etc.Sensory evaluation found that TSPC8 is better than TSPC4 and TSPC6 in terms of taste,aroma,shape and texture,but its color is relatively dull.(3)Proteobacteria and Firmicutes are the two main phyla of TSPC species.Lactobacillus and Weissella are the dominant genus of TSPC4;Lactobacillus is the most dominant genus in the whole fermentation process of TSPC6;while in the fermentation process of TSPC8,Lactobacillus and Lactococcus occupy relative abundance respectively The first and second place.LEfSe analysis found that salt content is one of the main factors affecting the microbial flora structure of natural fermentation toona sinensis.(4)Spearman correlation was used to analyze the correlation between 49 genera and 108 compounds in TSPC.The results show that microorganisms have the most important influence on amino acids,with a correlation of 100%,followed by organic acids.There are three organic acids,lactic acid,acetic acid,and ascorbic acid are related to microorganisms.18 genera in TSPC4 are related to 27 flavor substances;28 genera in TSPC6 are related to 33 flavor substances;35 genera in TSPC8 are related to 34 flavor substances.The flavor substances related to Lactobacillus are the most.(5)Based on the above conclusions,TSPC4 has large acid production,fast acid production rate,short fermentation time,high total phenol content and strong antioxidant capacity.It has the largest number of lactic acid bacteria in the fermentation process;and TSPC8 has high amino acid content and rich volatile compounds.the sensory quality is better.Therefore,in industrial production,the appropriate amount of salt can be selected according to production requirements.