Isolation, Identification And Selection Of The Yeasts From Traditional Fermentation Soybean Paste In Heilongjiang Province

Fermentation soybean paste is one of the most important traditional fermentation soybean products in China that is being populared increasingly for its nutrition and health care role. It is welcomed at meals all the time. Nowadays most products were produced by natural fermentation, so the quality of soybean paste is insTab. and not safe enough. In the mean while people have a strong desire to improve the flavor, nutrition and security of the products. In order to shorten the fermentation period, improve the technology and get better product, this project studied the whole fermentation process of the traditional fermentation soybean paste, and some good strains were selected for the industry.Microorganisms play a leading role in the whole fermentation progress of soybean paste. As is reported the yeast have heavy correlations to the flavor and the quality of the soybean paste. So investigating the species of the yeasts and their functions will be very useful to improve the technology and quality of the soybean-paste. In the present thesis, the samples of soybean paste in. Heilongjiang province were investigated, then the yeasts in the paste were isolated and identificated. At last the alcohol and whole ester were taken as the main indicatrix, and four strains of the yeasts were screened from nature fermentation soybean paste. Their fermentation properties and component changes during the fermentation period were studied. The main results are as following:1. The microorganism of a representative traditional fermentation soybean paste was analyzed. The changes of microorganism system were analysed, and also the changes of physical and chemical properties were studied. The optimum time of sample gathering of traditional fermatation soybean paste was at the midanaphase of the whole fermentation process (20-30 days).2. Twenty-four Soybean paste products were studied in Heilongjiang province, fifty-eight strains of yeast were isolated and all of them were identified. They belong to eight generas. There were twelve strains of Hansenula consisted of one strain of H.subpelliculosa, four stains of H.anomala, three stains of H.sydowiorum and two stains of Hansenula ciferrii. Among the fifteen strains of Candida, five of them belong to C.lambicus, and eight of them belong to others. Another three stains of yeast belong to Zygosaccharomyce, all of them are Z.majors. There are four stains of Debaryomyces hansenii and eight stains of Geotrichum candidu. There are eight...