Preliminary Research On Quality Of Broad Bean Paste

Soybean paste was one of the traditional fermented soybean products in our country. It was popular with many people by its nice taste in quality, rich nourishment, delicious flavor and the prospect of market was extensive. But there were many procedures in the production and the fermentation of soybean paste was a complex course of metablism of microorganisms. So it may cause some quality problems and the white particles was one of them which severely effects presentation quality of soybean paste. Another problem was that the production cycle of traditional fermentation was very long (about 4 months). Compared with high temperature fermentation (about 1 month), the flavor of soybean paste with traditional fermentation was better. Based on these facts, we have studied component of the white particles and the effect of the technological parameters on the content of tyrosine, and then we made soybean paste with the domesticate Aspergillus oryzae in order to reduce the content of tyrosine. Analyzed the microbial flora in the mature soy sauce mash of traditonal fermentation and volatile flavor compounds of the two production processes for the further improvement of flavor with high temperature fermentation.In this study, we concluded that:The white particles in soybean paste included a mass of tyrosine and a spot of phenylalanine. In order to decreased content of tyrosine in soybean paste, manipulation of technological parameter should be paid attention which include properly controlling starter proagation time and fermentation time, the amount of salt addition and water addtion. Moreover we added 14 mL glacial acetic acid to per kg koji to help to reduce the content of tyrosine with no influence to the flavor.Added tyrosine to wort medium to demesticate Aspergillus oryzae. The abilities of producing acidic or neutral protease of acclimated Aspergillus oryzae were separately decreasing compared to the productive Aspergillus oryzae. We applied acclimated Aspergillus oryzae to fermentation and used the same processing parameters as soybean paste manufacturing. At the intermediate stage of fermentation, amino acid produced by productive Aspergillus oryzae and acclimated Aspergillus oryzae were detected, we found that the content of tyrosine in soybean paste produced by the latter was remarkable decreasing. So using the acclimated Aspergillus oryzae to fermentation will help to prevent the formation of white particles.Culture-independent approach (Clone library technique based on small subunit rRNA gene) was used to analyze the bacterial 16s rDNA and fungal 18s rDNA of the sample. The results indicated that the bacteria existed in mature soy sauce mash belong to these genus: Staphylococcus,Lactobacillus and Tetragenococcus respectively. Similarities with the nearest species were from 98 % to 99 %. The fungi existed were Zygosaccharomyces, Rhizochaete, Aspergillus, Rhodotorula and Phaseoleae environmental sample, Similarities were 99 %.Headspace solid phase microextraction combined with gas chromatography-mass spectrometry (HS-SPME-GC-MS) was used to analyze the volatiles in mature soy sauce mash of traditonal fermentation and high temperature fermentation respectively. The results showed that the types of main volatiles in traditonal fermentation sauce mash were more than those in high temperature fermentation sauce mash including alcohols, aldehydes, esters, ketones, hydrocarbons, heterocycles, nitriles, acids, aethers, phenols. Relative contents of esters, aldehydes, hydrocarbons and heterocycles in traditional fermentation were more than those in high temperature fermentation.