Koji is a term that describes the process of molds growing and producing enzymes that hydrolyze complex components in cooked materials into simpler compounds. In this study, the optimal conditions for the production of enzymes (amylase and protease) of koji incubation were determined by using the response surface methodology with the central composite design 22 + star. The experiments were conducted with two factors, including molds addition (X1) (0.02 ÷ 0.04%) and koji-making time (X2) (24 ÷ 36 hours), as well as incubation temperature (X3) (27 ÷ 33°C) and pH of koji (X4) (5.5 ÷ 6.5). The study results showed that the mycelium of Aspergillus oryzae developed a fairly thick layer on the medium at 0.030 ÷ 0.044% of molds addition and 30 ÷ 36 hours with pH 5.89 ÷ 6.12 and temperature 29.76 ÷ 30.24°C. The optimal conditions (molds addition, time, pH, and temperature) were 0.03%, 30 hours, pH 6.0, and 30°C, respectively. In these optimal parameters, amylase and protease activities were 61.35 and 12.27 U/g dry matter, respectively.
Key words: amylase; Aspergillus oryzae; Koji; oyster mushrooms; protease.
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