Antioxidant
Japanese: 抗酸化物質（アンチオキシダント）
Substances that prevent damage from reactive oxygen species and radicals. Fermentation increases antioxidants such as melanoidins and isoflavones.
Antioxidants are substances that neutralize reactive oxygen species and free radicals, preventing oxidative cell damage. Vitamin C, vitamin E, and polyphenols are classic examples.
Fermentation has the effect of increasing antioxidants. Melanoidins from the Maillard reaction possess antioxidant activity, and research suggests longer-aged miso has greater antioxidant power. Soy isoflavones are also converted during fermentation into 'aglycone' forms that are more easily absorbed.
Darker miso tends to have higher antioxidant capacity—color change is not merely visual but also functional. Fermentation elevates the nutritional value of ingredients in invisible ways.