Study On Discrimination Technology Of Origin And Process Feature Of Pixian Broad-bean Paste

In this thesis,the differences in physicochemical properties and volatile components of bean paste from Pixian and non-Pixian production areas were investigated.The discrimination model of Pixian broad-bean paste was systematically established,and the key volatile components of Pixian broad-bean paste were identified.The changes of microorganisms and volatile components in the post-fermentation stage of Pixian broad-bean paste were studied.The main results are as follows:The differences in physicochemical properties of 20 different brands bean paste samples were analyzed.The reducing sugar,amino acid nitrogen,total acid,total ester and moisture contents were 1.73～7.77 g·（100g）^-1,0.42～1.13 g·（100g）^-1,0.28～1.43 g·（100g）^-1,0.47～0.63g·（100g）^-1,42.80～60.06%,respectively.The feasibility of tracing the origin of Pixian broad-bean paste by analyzing volatile compounds in different broad bean pastes was investigated.A total of 87 volatile compounds were detected in 105 bean paste samples from different manufacturing origins by headspace solid phase microextraction gas chromatography mass spectrometry（HS-SPME-GC-MS）.Using chemical metrology software to filter and analyze the data,the identification model based on volatile compounds was successfully constructed.Orthogonal partial least squares discriminant analysis（OPLS-DA）revealed 45 compounds with variable importance for the projection greater than 1.Using Fisher discriminant analysis,15 volatile compounds were further identified as effective traceability indexes.The overall correct discriminant rates of Fisher discriminating models were 95.9%,and all the samples in the validation set were correctly classified.The effects of the post-fermented bean paste on the changes of volatile compounds and microbial communities were investigated.A total of 119 volatile compounds were detected in the post-fermentation process of bean paste.With the progress of fermentation,the relative content of alcohols increased first and then decreased,while the relative content and quantity of esters increased continuously.High throughput sequence was used to analyze the changes of microorganism communities during the fermentation of bean paste.At the phylum level,Proteobacteria and Ascomycota were the dominant microorganism in fermentation period of bean paste.At the genus level,Wickerhamomyces was the dominant fungi in the post-fermented bean paste.Staphylococcus,Weissella and Bacillus were the dominant bacteria in the initial stage of fermentation,while Escherichia-Shigella,Tetragenococcus and Lactococcus were the dominant bacteria in the late stage of fermentation.