大豆麹を加えた味噌原料の熟成中の抗酸化性の変化

抄録

The antioxidant capacity of food is vital for maintaining our health, and miso is a food rich in antioxidants. We used soybean koji, the antioxidant content of which we expected to be high, as an ingredient of rice koji miso, and we examined the effect of the proportion of added soybean koji on the antioxidant capacity of miso during preparation and maturation. The oxygen radical absorbance capacity (ORAC) value was used as a measure of the antioxidant capacity of miso in this experiment. The ORAC value of soybeans was 10 or more times higher than that of rice. The ORAC value of rice did not change after immersion of the rice in cold water but increased by 3.2 times after the production of koji. The ORAC value of steam-boiled soybeans increased by 1.2 times after the production of koji, and that of crushed soybean koji was 1.6 times that of steam-boiled soybeans. The hydrophilic antioxidant content values were higher than the lipophilic antioxidant content values in both rice and soybeans. Maturation testing showed that the greater the amount of soybean koji used in the miso, the greater the increase in antioxidant capacity. The final ORAC value was 176.3 μmol TE/g for miso without soybean koji and 460.9 μmol TE/g for miso with soybean koji added at 60% of the total ingredient weight. The ORAC values after 8-weeks of maturation were 2.4 to 3.7 times those before maturation. Our results demonstrated that soybean koji can improve the antioxidant capacity of rice koji miso.