Optimization Conditions of Koji Making by Aspergillus oryzae 1228 and Study on Soy Sauce Brewing

Using soya bean meal and wheat bran as material,Aspergillus oryzae 1228 was selected for koji making.By single factor test and orthogonal experiment,the optimum processing conditions of koji making were obtained.The brewing experiment of soy sauce was conducted by low-salt solid-state fermentation.The best conditions were as follows: soya bean meal to wheat bran ratio 6:4,water content 90%,inoculating scale 0.5% and koji making for 32 h.Under the optimized conditions,the neutral protease activity in koji was 1473 U/g.After 20 days for fermentation,the contents of amino acid nitrogen and soluble saltless solid were 6.90 mg/mL and 163.60 mg/mL respectively in the soy sauce.The soy sauce showed good flavor and color.