【Reading】こまい

【English Name】Aged Rice

Komai (old rice) refers to rice that remains in inventory even after the year in which it was harvested has passed. The rice crop year (November to the following October) serves as the standard for classification, and the distinction between new rice (shinmai) and old rice arises with November 1 as the turning point, though there is no strict definition established by law.

In its relationship to sushi, old rice is highly valued as a presence for use as shari. Because it has lower moisture content than new rice and possesses the property of allowing good vinegar penetration, it is not uncommon to see sushi restaurants use old rice alone, or blend it with new rice.

If storage conditions are favorable (particularly in a low-temperature environment), old rice up to about one year after harvest can maintain a quality close to new rice. However, once two years pass, deterioration progresses visibly, and from the decomposition reactions of lipids, components such as pentanal and hexanal are produced, giving rise to a distinctive smell called "komai-shu" (old-rice odor). A decline in water absorption and hardening of the grains when cooked also come to be observed.

Furthermore, as the years of storage increase, names that stack the character for "old" (ko) are given, such as ko-komai (two years prior) and ko-ko-komai (three years prior). Looking historically, in medieval and early-modern Japan, old rice—which had the property of increasing in volume when cooked—was traded at prices exceeding those of new rice. In 2025, Lawson sold rice balls (onigiri) bearing the name "vintage rice" for old rice, drawing great public interest.