[an error occurred while processing this directive]
Chestnut is the fruit of the chestnut tree (Castanea), a native to temperate regions of the Northern Hemisphere. The fruit is contained in a spiny and sharp cupule called burr, 5-11 cm in diameter. The burrs are often borne in pairs or in clusters on the branch. Each burr contains one to seven nuts, according to species, varieties and cultivars. The burr will turn yellow-brown and split open in two to four sections when the fruits reach maturity, and fall to the ground.
The chestnut has a pointed end with a small tuft at its tip, and at the other end, a hilum - a pale brown attachment scar. In many varieties, the chestnut has one or two flattened sides. Each chestnut has two layer of skins. The outer layer is a hard, shiny, brown husk called pericarpus (in industry, this is called peel), and a second layer called pellicle or episperm, which is thinner and closely attached to the nut, following the grooves usually present on the surface of the nut. The grooves are of variable sizes and depths according to the species and variety. The nut consists of two cotyledons with a creamy-white flesh throughout, except in some varieties where there is only one cotyledon, and with episperm that is only slightly or not intruded at all. These varieties usually have one large, well-rounded (no flat surface) nut per burr, and these are called marron, such as 'marron de Lyon' in France, 'marron di Mugello' in Italy, or 'Paragon'.
Fresh chestnut has about 180 calories per 100g of of edible parts, much lower than that of walnuts, almonds (600 kcal/100g). The nut also contains no cholesterol and very little fat, mostly unsaturated, and no gluten. Chestnut has twice as much starch as the potato, and about eight percent of various sugars, mainly sucrose, glucose and fructose. It is also the only type of nuts which contains vitamin C, with about 40 mg/100g of raw product. The amount of vitamin C decreases with heating.