| Lentinus edodes is one of the well-established edible mushrooms in China.Owing to its unique flavor and nutritional value,more and more processed products with Lentinus edodes as the main raw material are coming into people's life.Recently,the processing methods and influence on the flavor of Lentinus edodes have gradually become a research hotspot.However,it mainly focuses on the effects of drying,enzymatic hydrolysis,blanching and boiling on the content of flavor substances,and there are relatively few researches on the release of characteristic flavor by fermentation,especially the mechanism of flavor formation.Therefore,the fermentation strains of Lentinus edodes were screened,and the fermentation parameters were optimized in this paper.On this basis,the odor-active and taste-active compounds of fermentation broth were investigated,the changes of flavor substances in the formation process of Lentinus edodes were explored,and the theoretical basis was provided for the effective regulation of characteristic flavor of Lentinus edodes fermentation broth.The research contents were as follow:1.Theoretical screening and experimental verification of mushroom fermentation strains.The umami substances of fermented shiitake mushrooms using Saccharomyces cerevisiae,Aspergillus oryzae,Aspergillus niger and Lactiplantibacillus plantarum were investigated.The results showed that the four strains all had the ability to enhance the flavor of Lentinus edodes.And the contents of free amino acids and flavor nucleotides in the fermentation broth of Lentinus edodes fermented by Lactiplantibacillus plantarum were higher,which had the ability to enhance the flavor more obviously.2.The optimization of fermentation process.By comparing and analyzing the acidity,flavor substance content and equivalent umami concentration of fermentation broth under different fermentation conditions,using single factor and response surface analysis,the optimal parameters were determined: Shiitake mushroom pilei:fermentation time 4 d,powder amount 1.5 g,inoculation amount 4.5% and fermentation temperature 40?;Shiitake mushroom stipes: fermentation time 4 d,powder amount 1.5 g,inoculation amount 4.2% and fermentation temperature 30?.3.The changes of taste substances in the fermentation process.By evaluating the taste attributes of fermentation broth,analyzing the difference of taste of different samples,measuring the content of taste substances,analyzing the changes of taste substances,and determining the possible key taste substances through correlation analysis.The results showed that fermentation by Lactiplantibacillus plantarum changed the original single and light taste into complex and mellow taste.The fermentation broth with different fermentation time had different texture and taste characteristics.In the fermentation process,the contents of most flavorings(6 organic acids,17 amino acids,4 5'-nucleotides)increased;And correlation analysis showed that23 flavoring substances were highly correlated with taste attributes.4.The changes of aroma substances in the fermentation process.By evaluating the olfaction properties of fermentation broth,measuring the types and contents of volatile components,analyzing the difference and changes of aroma substances of different samples,and determining the possible key aroma substances through correlation analysis.The results showed that fermentation by Lactiplantibacillus plantarum could effectively improve the aroma,and changed the original characteristic flavor of Lentinus edodes into a variety of aroma with rich layers.The fermentation broth of Lentinus edodes with different fermentation time had different aroma characteristics.After HS-SPME-GC-MS analysis,71 volatile compounds were identified in all samples,including 11 aldehydes,4 ketones,7 acids,7 esters,6 alcohols,22 hydrocarbons,5 sulfur compounds,7 nitrogen-containing compounds and 2 other compounds.And correlation analysis showed that 25 compounds were highly correlated with olfactory attributes. |
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