It seems that these enzymes were active until the internal
temperature of the koji attained to 75°C. Furthermore, in the case of
heating at 75°C, the glucose concentration and amino nitrogen
content, which were substrates of Maillard reaction slowly decreased
with an increase in the number of days after the peak levels. These
decreases seem to correlate with the progress of the Maillard reaction.
Effect of stepwise heating on the antioxidant activity of
HP-koji These results suggested that the enzyme and Maillard
reactions by heating contributed together to enhance the antioxidant
activity of HP-koji. Therefore, we hypothesized that it was able to
increase antioxidant activity of HP-koji more effectively through 2
heating steps. First, the enzyme reactions are promoted at a moderate
temperature, such as 55°C, to facilitate the production of amino acid
and reducing sugar, which serve as substrates for the Maillard
reaction. Second, HP-koji is further incubated at a higher temperature,
such as 75°C, to promote Maillard reaction