Isolation Of Specific Yeast Strain For Soybean Paste Fermentation And The Optimization Of Fermentation Technology

The paper made a research on the fermented process of traditional soybean sauce, which was mainly investigating the miso and soy sauce by making using of the features of aroma yeast. The growth curve of yeasts in miso medium:delayed period from beginning to the6hours; accelerated period from the6th-12th hours, logarithmic growth period from the12th-27th hours, the stable period from the27th-36th hours, and recession period after the36th hours. The growth curve of yeasts in soy sauce:delayed period from the beginning to6hours, accelerated period from the6th-15th hours, logarithmic growth period from the18th-27th hours, the stable period from the30th-39th hours and recession period after the39hours. By the test of yeast, it separated strain Y2named WJ01which was suitable for soy sauce production. The breeding way of strain Y2was unilateral budding, its cell was spherical and single colony was white. The surface of the strain Y2was smooth and moist, thick texture, regular edge. It was not easy to form pseudohyphal. The strain Y2produced ascospores, maked glucose ferment and maltose, and its strong alcoholic fermentation being different from nitrate growed in18%salt environment and breeded well in10%salt matrix environment. The strain Y2was not suitable in high temperature. According these features above and retrieval table, this strain was Zygosaccharomyces rouxii.Compared with the strain WJ save in lab, I choosed the strain in the culture medium of very low bean sprouts liquid and nurture it for its strong ability in producing ester and alcohol, in recovering power, fermenting power. Finally, I determined WJ01used for production due to the test in a very low temperature.The best growth condition in soy sauce culture medium was NaCl with the dense of6%-8%. pH4-5, and glucose with the dense of about5%. The final optimized soy sauce miso medium was soy sauce juice7%, glucose with the dense of7.8%. pH4.5and added NaCl with the dense of7%.In order to determine the optimal proportion of two strains, a L9(33) orthogonal experiment design was conducted to study the proportion of lactic acid bacteria and saccharomycetes. The results were that lactic acid bacteria and saccharomycetes were inoculated into soybean paste in the10days, however, the inoculation concentration of both was5×106cfu/g and5x105cfu/g respectively. The taste, chemical and physical characteristic and flavors of that fermented by lactic acid bacteria saccharomycetes, were better than that only fermented by single Aspergillums oryzae.This paper described the formation mechanism of pea sauce color, smell, taste, through orthogonal test optimized conditions of soybean sauce fermentation40days, research on the effects of water added, salt added, fermentation temperature, the time of koji making and combined with sensual evaluation, obtain the best technology parameter, the optimum process conditions for salt added,added water quantity was56%, added salt component was10%,fermentation temperature was40℃, the time of koji making was40h. Further studied the effect of different time of koji making on amino acids of significant differences. The Result proved that the highest of amino acid content after40hours.