Fermentation Performance Comparison Of Aspergillus Oryzae Rib40and3.042in Soy Sauce

The Japanese soy sauce is of distinctive flavor, and has become the most competitive product in international market. Affected by dietary habits, Japanese soy sauce tastes light and mellow, which is more suitable for dipping. Along with the integration of food culture, Japanese soy sauce becomes more and more popular among our consumers. In order to improve the quality of Chinese soy sauce and open the international market as soon as possible, comparative study of Chinese soy sauce and Japanese soy sauce is significant. The selection of koji species has great influence on the quality of soy sauce. In this paper, the fermentation performance differences between A. oryzae3.042and A. oryzae RIB40was compared, using low-salt solid-state and high-salt liquid-state two fermentation methods. The two meters including the koji spore numbers, koji preparation, physical and chemical indicators of the fermentation process, organic acids content, soy sauce flavor and the influence of adding yeast on the quality of soy sauce were compared. The study provided guidance for choosing soy sauce koji making strains to meet the needs of different kinds of soy sauce and fermentation methods.It was found that compared with A. oryzae RIB40, A. oryzae3.042had stronger spore ability, the spore number of72h was1.85times of A. oryzae RIB40in the study of koji growth, so A. oryzae3-042could be better adapt to the environment in production. The enzyme activity characteristics of the two meters Aspergillus were identified. The glucoamylase activity of A. oryzae RIB40was more prominent, therefore, when there was great amount of starch material, it could make better use of the substrate; A. oryzae3.042was characterized by high protease activity and balanced glucoamylase and cellulose activity, which could break down the raw materials that had bigger content of protein better.In low-salt solid-state process condition, at the end of the fermentation, A. oryzae RIB40had2.2g/100mL reducing sugar,10%higher than3.042, and0.73g/100mL ethanol,12%higher than3.042. The content of lactic acid of A. oryzae RIB40was about2.5times of3.042and the content of acetic acid was1.28times of3.042. The soy sauce of A. oryzae RIB40had a high content of alcohols and phenols, therefore, the soy sauce of A. oryzae RJB40was mellow, and A. oryzae RIB40had a high content of aldehydes and ketones. A. oryzae3.042had an advantage in esters, so the soy sauce of A. oryzae3.042was of more ester aroma.In high-salt liquid-state process condition, at the end of the fermentation, A. oryzae RIB40had higher ethanol content,0.89g/100mL,8%higher than3.042. The content of lactic acid was about2%higher than3.042, and the content of acetic acid was5.6%higher than3.042. In the high-salt liquid process condition, using A. oryzae RIB40and A. oryzae3.042to make koji, the results of the diffrence of soy sauce flavor was similar to that of low-salt solid-state process condition. The flavor of soy sauce from two Aspergillus strains was quite different:using A. oryzae RIB40to make koji, mellow flavor of the soy sauce was more prominent; while using A. oryzae3.042, the soy sauce was of more ester aroma.In addition, the study revealed that adding yeast caused the pH of sauce mash decreased rapidly, total acid content increased, sugar content reduced and the ethanol content increased. The results of flavor substances tests showed that the addition of yeast could significantly improve the relative content of alcohols and esters. Therefore, according to the product needs, appropriate strains can be selected in actual production.