| Watermelon sauce beans are a local specialty food in Heze region,made by natural fermentation of fresh watermelon and soybeans as raw materials.At present,there are few research reports on watermelon sauce beans,mainly focusing on the production methods and nutritional analysis of soybean sauce.There are no reports on the microbial diversity,metabolic product changes,and flavor composition of watermelon sauce beans at different fermentation stages.In this study,fresh watermelon and soybeans were used as raw materials and watermelon jam beans were obtained through natural fermentation.high-throughput sequencing technology,ultra performance liquid chromatography-mass spectrometry(UPLC-Q-ExactiveMS)technology and headspace solid phase microextraction(HS-SPME-GC-MC)technology were used to study the changes of microbial diversity,metabolites and flavor substances during the fermentation of watermelon jam beans,Provide theoretical basis for the research and development and standardized production of Heze watermelon sauce beans.The main research content and results are as follows:1.Study on the changes in bacterial community structure of watermelon sauce beans under different fermentation periods.Using 16S rRNA gene sequence analysis technology,the bacterial diversity during the fermentation process of watermelon and soybean sauce was analyzed and studied.The results showed that a total of 576579 effective sequences and 1385 OTUs were obtained from the three groups of samples fermented for 2,15,and 30 days,annotated into 22 phyla,50 classes,114 orders,178 families,and 3 18 genera.Firmicutes is a dominant phylum,with the main dominant bacteria being and Tetragonococcus.2.Study on the structural changes of fungal communities in watermelon and soybean sauce during different fermentation periods.Using ITS gene sequence analysis technology,the diversity of fungi during the fermentation process of watermelon and soybean sauce was analyzed and studied.The results showed that a total of 753942 effective sequences and 91 OTUs were obtained from the three groups of samples fermented for 2,15,and 30 days.Annotated to 6 phyla,11 classes,25 orders,39 families,and 43 genera;In the whole fermentation cycle of watermelon sauce beans,Ascomycota is the absolute advantage category,and Aspergillus is the dominant genus.3.Metabolite analysis was conducted on watermelon sauce beans during the fermentation process using a high-performance liquid chromatography-mass spectrometry(HPLC-MS)method.A total of 263 differential metabolites were identified among the samples collected on days 2,15,and 30 of fermentation,with nucleosides having the highest relative content(12.94%),followed by esters(4.71%)and organic acids(3.53%).The metabolite content remained relatively stable during the later stage of fermentation compared to the mid-stage,indicating that the late fermentation stage is the optimal period for nutrient enrichment in watermelon sauce beans.4.Volatile compounds in watermelon sauce beans were analyzed during different fermentation stages using headspace solid-phase microextraction(HS-SPME).A total of 49 flavor substances were detected among the samples collected on days 2,15,and 30 of fermentation,including 9 alcohols,8 esters,3 acids,2 aldehydes,3 ketones,3 olefins,2 ethers,and other compounds.Alcohols,esters,and acids were the major volatile components in watermelon sauce beans,with 1-octen-3-ol,1-hexanol,methyl palmitate,ethyl linoleate,and adipic acid being the most abundant compounds.The content of alcohols and acids decreased gradually as the fermentation time increased,while the ester content initially increased and then decreased.In summary,bacterial fermentation was the dominant process during the entire fermentation process,while fungal diversity was only enriched in the early stages.The major metabolites in watermelon sauce beans were nucleosides,alcohols,and organic acids,and the main volatile flavor substances were alcohols,esters,and acids. |
PDF Full Text Request