Kuri / Japanese Chestnuts

Japanese chestnuts are low in fat and rich in carbohydrates, making them a good source of energy, while also containing vitamin B1, which is essential for carbohydrate metabolism. These chestnuts are also composed of dietary fiber, which helps regulate the intestinal environment and promotes regularity. They are also rich in vitamin C. The vitamin C in Japanese chestnuts is wrapped in starch, so it is relatively resistant to degradation even when heated. These nuts are also rich in potassium, which helps to excrete sodium and keep blood pressure within normal ranges, making these chestnuts useful for preventing high blood pressure.
By eating Japanese chestnuts without peeling the brown layer just under the hard shell, you can consume the tannins contained in this inner skin. Tannins are a type of polyphenol that have antioxidant properties and are known to have anti-aging effects.

Storing Japanese chestnuts at low temperatures increases their sweetness, so it's best to keep them in the refrigerator for 3 to 4 days before cooking for deeper flavor. They can also be frozen, which softens the hard outer shell, making it easier to peel.

Chestnuts are encased in a hard outer shell called the "onikawa" and a thin inner skin called the "shibukawa." The onikawa corresponds to the fruit flesh of other fruits, while the edible part of the chestnut is the seed. When sold, the spiky outer husk (iga) has been removed, which is actually part of the chestnut’s skin.

If the outer shell has small holes, the chestnut may have been eaten by insects. Soaking chestnuts in plenty of water will make the damaged ones float, allowing you to separate these out before cooking.