Study On The Formation And Application Of Flavor Substances In Multi-strain Fermentation Of Soy Sauce

Soy sauce, a important component of traditional condiment, is very popular to people in the diet of living for its long history. With the improvement of living standard, soy sauce with higher quality and functionality was more favorable. After China's accession to WTO, the domestic markets of soy sauce are facing the impact, and foreign markets are mainly occupied by Japan and South Korea. Therefore, in order to satisfy people's demand and enhance China's competitiveness of soy sauce, it is essential to strengthen the quality and flavor of soy sauce. In this study, the single Aspergillus oryzae fermentation process for soy sauce which appeared weak enzyme and poor soy sauce flavor was adapted by multi-strain fermentation.. Simultaneity, the backward fermentation process of low-salt was replaced by solid-state fermentation.And also a method assaying flavor elements was confirmed, which could provide a theoretical and practical basis to improve the flavor and quality of soy sauce.With protease activity as an target, the conditions impacting koji of Aspergillus oryzae were optimized. Effects of different fermentation conditions on the amino nitrogen and color rates were studied. The optimal conditions for protease-yielding by Aspergillus oryzae was 6:4 ration of soybean meal and wheat bran,90% of moisture content and 48h of fermentation. After 15-days fermentation, the amino nitrogen in soy sauce was tend to be stable, and the increase of color rate began to slow down. The amino nitrogen content of soy sauce was up to the peak value with 12% of salt water. And the deepest color of soy sauce was appeared with 10% of salt water. The content of amino nitrogen in soy sauce was improved with the increaseing of soybean meal. However,The content of wheat bran affected the color rate of soy sauce in certain extent.The volatile flavor substances in soy sauce were separated and assayed by solvent extraction method and gas chromatography external standard method respectively. And twelve species of flavor substances were all detected in soy sauce. At the same time, the concentration of salt, soluble salt-free solids, total nitrogen, amino nitrogen and total acid,5 kinds of physical and chemical indicators were measured, which had reached the national standard requirements. The utilization of raw protein and starch in soy fermentation had reached a greater level in the factory.The effects of adding Aspergillus niger, Monascus and yeast during Aspergillus oryzae fermentation were studied respectively. The results showed that the addtion of Aspergillus niger increased the content of amino nitrogen, reducing sugar and deepened the color of soy sauce. The addtion of Monascus improved the color of soy sauce and made soy sauce ruddy and bright. Simultaneously, the content of ethanol and ethyl acetate in soy sauce were improved, which made soy sauce more mellow. Yeast-added in soy sauce increased the content of ethanol and ethyl acetate, which strenthened the mellow flavor of soy sauce.A industrial fermentation process for high-quality soy sauce by solid-thin fermentation using multi-strain was successfully established. The changes of flavor compounds such as amino nitrogen, total nitrogen, reducing sugar, ethanol, ethyl acetate and acetic acid during multi-strain fermentation of soy sauce were studied, which would lay the foundation for the thin-solid fermentation with multi-strain and enhancement of flavor in soy sauce.