Soy Sauce Fermented From Koji By Aspergillus Oryzae And Monascus Sp. With Corn Starch Cake As The Main Raw Material

Corn starch cake is rich in protein and carbohydrate contents.The total protein and carbohydrate amounts in corn starch cake were 23-30% and 20-30% respectively.The heavy metal amounts meeted the requirements of food grade.Corn starch cake was in large output and low price,but it has not been used reasonably until now.In this article,we mainly studied the production of valuable products by using the corn starch cake as raw material via microbial fermentation to realize the recyling of resources.In this article, we studied the characters of soy sauce fermented by Aspergillus oryzae and Monascus sp.,which were cultured by corn starch cake as raw material.The main purposes were to reduce the cost of soy sauce,and solve the utilization problem of corn starch cake.Koji cultivation by Aspergillus oryzae with corn starch cake as main material was investigated.The optimized culture conditions were as follows:the forced filling rate:28 g/500 mL Erlenmeyer flask; inoculum volume:10%;intial water content:50%,the bran amount:16 g(dry basis),the rate between corn starch cake and soybean:8:2; fermentation temperature:30℃; fermentation time:72 h.The neutral protease activity could reach to 3000 U/g(dry basis), glucoamylase activity:80 U/g(dry basis). The protease activity meeted the requirement for industrial production.Submerged fermentation of Monascus pigment by Monascus sp.with corn starch cake as main material was inverstigated.The optimized results were as follows:experimental microorganizm:9903A;liquid volume:85 mL/500 mL; corn starch cake (dry basis):7.5%; nitrogen:corn steep liquor and its concentration was 8%; Zn2+ and Mn2+ concentration were 0.06 g/L and 0.03 g/Lrespectively;inoculation volume:10%(v/v); cultivation fermentation:32℃; cultivation time:9d; speed:180 r/min. On these conditions, the color value of Monascus fermentation broth could reach to 230 U/mL.The amino nitrogen content and total nitrogen content reach to 0.71 g/100 mL and 1.19 g/100 mL respectively, the reducing sugar in the soysauce is 1.32 g/100 mL.The physical and chemical indexes all meet the requirements of the National Standard for soy sauce. But the color ratio and red relex of the soy sauce were not very well,becauce the yield of Monascus pigment produced by submerged fermentation with corn starch cake was low.The stability of red pigment in soy sauce maintain good effect during storage.It is concluded that the Monascus pigment added during the fermentation of soy sauce would be better for application.The addition amount was 0.2%(m/v) (the color value of the monascus pigment was 8760 U/g). Monascus pigments will be degraded and unstable on the effect of light.In order to maintain the stability of Monascus pigments in the soy sauce,this paper studied that soy sauce should be stored avoiding light.