| Bagongshan sufu is made from soybean and fermented for several months in an open environment.The post-leavening period of sufu is an important stage for the quality change of its flavor and nutrition.Therefore,the study of microorganism and flavor nutrition in the post-leavening process of sufu in Bagongshan has an important role in the monitoring and optimization of the development of high-quality sufu.In this paper,Bagongshan sufu was taken as the research object.The headspace solid-phase microextraction-gas chromatography-mass spectrometry combined technology was used to optimize the extraction conditions of Bagongshan sufu and the post-fermentation of Red sufu,White sufu and Oil sufu was studied.The types and contents of volatile flavor substances in different stages of three kinds of sufu were analyzed by reverse phase high performance liquid chromatography and OPA pre-column derivatization ultraviolet detection.And its physical and chemical properties were analyzed and compared.Bacterial colony changes were analyzed use high-throughput sequencing.The main results were as followed:(1)By optimizing the extraction conditions of flavor substances,the optimal conditions for extraction of Bagongshan sufu were as followed: the extraction temperature was 60 ℃,preheating time 20 min and 40 min extraction time.According to the flavor test,the Red sufu in the post-leavening period contains 50 kinds of volatile flavor substances,mainly 20 kinds of ester compounds and 9 kinds of alcohols;the White sufu in the post-leavening period contains 64 kinds of volatile flavor substances,mainly 26 kinds of ester and 10 kinds of alcohols;Oil sufu contains50 kinds of volatile flavor substances,mainly 19 kinds of esters,8 kinds of alcohols and 6 kinds of acids.OAV analysis showed that the main flavor substances were phenethyl alcohol,1-octen-3-ol,ethyl acetate,etc.,and the main content of aroma substances was Red sufu > White sufu >Oil sufu.(2)The content of free amino acids in sufu at different stages were determined.Among them,the total free amino acid content increases with the fermentation,and the content of free amino acids is White sufu > Red sufu > Oil sufu.The protease activity of the three kinds of sufu was detected by the forolin method,and the protease activity relationship was White sufu > Red sufu > Oil sufu in the beginning and middle of post-leavening period,and later the Red sufu > Oil sufu > White sufu.The physical and chemical properties ofthe three kinds of sufu were analyzed,and the three kinds of sufu had obvious differences in moisture,salt content,acidity and amino acid nitrogen.(3)The high-throughput sequencing method was used to analyze the bacterial colonies,and it was found that the dominant bacterial groups in sufu were Bacillus,Enterobacter,Acinetobacter and Tetralococcus etc.The Spearman correlation analysis of the flavor nutrition and bacterial flora of sufu in the post-leavening period showed that the amino acids were mainly related to a variety of core bacterial groups.Enterobacter is negatively correlated with most fragrance compounds;Bacillus is positively correlated with a variety of fragrance ester compounds;other strains,such as Lactococcus and Acinetobacte are also provided in the post-leavening period of sufu Good flavor.In summary,the research of this paper focuses on solving the main flavor nutrients and core microorganisms in the post-leavening period process of sufu and their interrelation.The research results can provide a research basis for the fixed-point regulation of sufu fermentation,and have guiding significance for the industrial production of high-quality sufu. |
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