Optimization of Koji-making Technology for Preparing Walnut Soy SauceThe koji-making technology was studied with the activity of neutral protease as index and walnut meal as raw protein material.The single factor experiment was used to investigate the effects of ratio of walnut meal,moisture content,steaming time and koji-making time on the activity of neutral protease.Based on single factor experiments,the koji-making technology was optimized by response surface methodology with four factors and three levels.The results showed the optimum koji-making conditions were as follows: the content of walnut meal was 55%,moisture content was 113%,steaming time was 32 min,time for koji-making was 32.9h.Under such conditions,the activity of proteases reached 1 002.87 U/g.