Optimization of fermentation conditions for preparing walnut soy sauce

The low-salt solid- state fermentation technology of walnut soy sauce was studied with the formation of amino acid nitrogen as index and walnut meal as raw protein material.The single factor experiment was used to set up the simulated quadratic polynomial regression equation of prediction model about independent variable and response value by using Box- Benhnken central composite design and response surface analysis theory. The results showed that the optimum fermentation conditions were as follows: the ratio of brine and material was 1.65, fermentation temperature was 45℃, fermentation time was 6d.Under above conditions, the amino nitrogen content reached to 0.835g /100mL, which was equal to the predictable value.