Isolation And Identification Of β-Glucosidases-Producing Non-Saccharomyces Yeast Strains And Its Influence On The Aroma Of Fermented Mango Juice

The aroma of fermented mango juice is mainly derived from the variety aroma components in the original fruit of mango,and its large number of aroma glycoside precursors in the peel-bound glycosides.The use of probiotics to further ferment mango juice to produce fermented mango juice can greatly improve the added value and economic benefits of mango products.The bound glycosides can be hydrolyzed byβ-glucosidase catalytic hydrolysis to release free volatile aroma glycosides,which make fermented mango juice exhibit typical aroma characteristics.Some nonSaccharomyces cerevisiae have strong extracellular enzyme production ability,and their mixing with lactic acid bacteria can enhance the complexity and regionality of the aroma of fermented mango fruit juice and improve the aroma sensory quality of mango juice.In this experiment,the purpose of this experiment was to select nonSaccharomyces cerevisiae with high yield of β-glucosidase from the vineyard soil of grapes growing all year round and applied it to the flavoring brewing process of fermented mango juice.(1)Preliminary studies have yielded the biological polymorphisms of isolated yeast strains in the soil environment of vineyards.Through the enrichment and cultivation of various soils in the vineyard,95 types of yeast were isolated.The strains producing β-glucosidase were screened by aesculin,and one non-Saccharomyces cerevisiae was isolated with lysine-containing plates.One strain(X1)has been selected and identified as Candida cf.sorbosivorans by internal transcriptional interval strip(ITS).(2)The physicochemical properties and adaptability of high-yielding strains,as well as some enzymatic properties,were studied.Experiments determined that the X1 strain was adapted to the fermentation environment of mango juice and the β-glucosidase produced was highly adaptable to the fermentation environment.Studies have shown that β-Glucosidase produced by X1 has a high enzyme retention rate between p H 3.0 to 5.4 and temperature 30 ℃ to 35 ℃.The changes of total sugar,total acid and other physicochemical indexes of mango juice before and after fermentation of X1 strain were studied.(3)The physicochemical properties of mango juice after fermentation were studied.After fermentation,the p H value of mango juice was 3.27,the soluble solids content was 12.59°Brix,the total sugar content was 118.73 g/L,the titratable acid content was10.55 g/L,the Vc content was 23.35 mg/100 g,the total phenol content was 74.1mg GAE/100 m L,and the total antioxidant capacity was 91.57 U/m L.(4)Based on non-targeted metabolomics methods,the changes of metabolites during the fermentation of mango juice were analyzed.C.cf.sorbosivorans X1 was active against phenols,terpenes,hexenes,and octenyl glycosides.The results showed that 41 metabolites in mango juice fermented by X1(X1FMJ)were identified as differential metabolites including 14 ester,4 hydrocarbons,3 aldehyde,5 ketone,4terpenoids,4 alcohol,1 aromatics,2 amine,1 acid and 3 heterocyclic compound.Through the analysis of the metabolic pathways of differential metabolites,5 key metabolic pathways were screened,namely tyrosine metabolism,phenylpropanoid biosynthesis,monoterpenoid biosynthesis,metabolic pathways,biosynthesis of secondary metabolites and Alpha-linolenic metabolism.These metabolic pathways have a promoting effect on the formation of FMJ flavor substances.