The Studies Of Bean Sauce Fermentation

Bean sauce is one of the traditional fermentation soybean products in our country whichuse broad bean and flour as raw material, by metabolic action of microorganisms, the rawmaterial were decomposed, and alcohols, acids and other flavor substances were produced.The traditional sauce is popular for its unique color, smell, taste and its health functions. Butdue to traditional natural fermentation need a long fermentation period, the productionprocess was vulnerable to undesired microbes contamination, products have no stable qualityand there are some security risks.In this paper,9strains of mold were isolated from two traditional natural fermented beansauce koji from different areas.3strains were selected for the koji making test by measuringthe spores number, protease activity and the casein hydrolyzate ability. After the koji makingtest by single microorganism, the strain No.1was identified as the strain which played themain role in koji making. The test of koji making by muti-microorganism was done becausethe single types of flavor substances of koji. The strain No.1and No.9were determined as themold starters for mix-fermentation.The two mold starters were identified by using traditional morphological methodsthrough observing the morphological characteristics and microscopic characteristics of colonythrough direct observation, shell vial assay and coverslip inserts method. The strains No.1andNo.9were identified as Aspergillusoryzae and Aspergillussoja respectively. The results on thephysiological characteristics showed that the optimum growth temperature for both strainNo.1and No.9were30℃; the optimum pH range for strain No.1was6.0~7.0,and6.0~8.0forstrain No.9; the optimum carbon source for strain No.1was sucrose, strain No.9was notsensitive to carbon source; and the growth of strain No.1and No.9in the culture medium withyeast extract powder and peptone as nitrogen source were far better than the other nitrogensources; and the No.1strain’s protease production time focused on48~72h, the optimumtemperature for enzyme production was30℃, and the No.9strain’s protease production timefocused on24~48h, the optimum temperature for enzyme production was27℃in shakingculture condition,. The mold starter is the base of koji making. The best mold starter conditions weredetermined after measured the spore number of starter. The conditions for strain No.1waswater content45%, sample loading quantity15g, inoculation amount0.3%, culturetemperature28℃; and water content42%, sample loading quantity25g, inoculation amount0.3%, culture temperature28℃were the suitable conditions for strain No.9. The optimumkoji-making conditions by using mixed No.1and No.9strains(1:1) were that flour and beanweight ratio was1:10,cultured56h at28℃with2%inoculation quantity through singlefactor and orthogonal experiments.The optimum conditions for bean sauce fermentation werestudied by using the content of amino nitrogen and aflatoxin B1content as evaluation standard.The conditions for fermentation by synthesizing two results of the orthogonal test were12%conditions salt concentration, the ratio of material to liquid1:2, fermentation for30d at45℃.Studies were done on the changes of water content, pH, total acid, amino nitrogencontent, reducing sugar content, non-enzymatic browning reaction degreeof traditional naturalfermentation bean sauce and artificial inoculated fermentation bean sauce during fermentation.The results showed that bean sauce product quality of this study reached the level oftraditional natural fermentation products.