Chestnuts are produced by seven species of tree within the Castanea genus. They have creamy white sweet flesh which appears in a number of cuisines, most famously roasted as a holiday food. Chestnut trees also provide valuable timber. Chestnuts can be found for sale in a number of forms, depending on the region of the world that the consumer is in. During the winter, many countries in the Northern hemisphere have whole fresh chestnuts for sale, but chestnuts can also be found preserved in water or syrup, or ground into flour.
The Northern hemisphere holds a number of distinct chestnut species, which have intermingled due to human introduction of preferred trees to different regions. All of the trees in the genus are deciduous, meaning that they lose their leaves every winter. The leaves of chestnut trees are simple and broad, with lightly serrated edges. A related species, the chinkapin, native to the American Northwest, looks very similar. The trees produce catkins, which mature into chestnuts in the fall. Each individual chestnut is enclosed in a spiny husk, which cracks open to reveal the brown-hulled nut inside.
When selecting whole chestnuts, consumers should look for smooth, glossy specimens which do not rattle inside the hull. Depending on the region, whole fresh chestnuts can be found roughly between September and February. Before they are hulled, the nuts can be stored in a cool dry place, and after the hulls are removed, they should be refrigerated. Chestnut flour should be kept under refrigeration until use. It can be used in ethnic recipes, or much like conventional flour.
One of the most classic preparations for chestnuts is roasting. To roast chestnuts, the hulls are slit so that they will not explode during roasting, either in an oven or in a fire. They are placed in a pan, and roasted for approximately 25 minutes, until the hulls become darker and more brittle. Consumers should be advised that the chestnuts are extremely hot, and they should not be peeled immediately, despite the intoxicating aroma.
In some ethnic cuisines, a ground flour made from chestnuts is used. Chestnuts are also used in Italian gelato, and they can be found ground into pastes, used in desserts, added to stuffings, and in many other dishes. Savory chestnut dishes such as ravioli are popular in Italy, especially with delicate creamy sauces which enhance the natural flavor of the sweet nuts.