Oxidation
Japanese: 酸化
A chemical reaction in which a substance combines with oxygen or loses electrons. Deeply involved in changes to the color and aroma of fermented foods.
Oxidation is a chemical reaction in which a substance combines with oxygen or loses electrons. A cut apple turning brown and iron rusting are both forms of oxidation.
In fermented foods, oxidation has two faces. Acetic acid fermentation is the oxidation of alcohol itself—a beneficial reaction that creates vinegar. But the discoloration of miso or soy sauce exposed to air is also oxidation, degrading flavor.
The darkening of miso color during aging involves oxidation alongside the Maillard reaction. Controlling the relationship with oxygen is what determines the quality of fermented foods.