Chestnuts are part of a group consisting of about nine species of trees and shrubs in the Fagaceae family. Although the shell is very difficult to remove, chestnuts are edible. However, it is rare to eat them raw and can even be dangerous for certain people (see below).
Chestnuts are more traditionally eaten when roasted, especially around the holidays. Roasting chestnuts takes away the raw and bitter flavor and replaces it with a sweetened one instead. People tend to indulge in sweets around Christmastime and other holidays, so it's no surprise that roasted chestnuts became a tradition for many families.
The Nut As a Vegetable
The chestnut fruit from the tree takes a bit of work to get to the nut itself. The nuts are encased in a spiky husk enclosure, with two to three nuts per each prickly burr. When mature, the fruit falls to the ground and is then shelled off the husk to get to the thin, smooth-shelled nut. You will most likely be buying chestnuts already separated from the outer husk.
Although we refer to them as nuts, the meat inside is soft and starchy, more akin to grains rather than crunchy, like traditional nuts. It is the only nut primarily treated as a vegetable due to its starch content. The European varieties are a bit larger in size than the native American variety. Horse chestnuts (generally considered inedible) and water chestnuts are considered a completely different species.
Beware of Raw Chestnuts
Certain people with severe intestinal issues, kidney problems, liver disease, and those who are pregnant, should avoid raw chestnuts. These nuts are usually boiled or roasted before eating due to the high levels of tannic acid. Ingesting high levels of tannic acid can cause stomach irritation, liver damage, or kidney damage. Tannic acid is a particular form of tannin, which is a type of polyphenol. It is formed in nutgalls by insects on twigs of specific oak trees. Chestnuts should be cooked completely in order to avoid digestive discomfort.
How to Prepare Chestnuts
The nuts are cured for about a week to permit their starch to develop into sugar, thus sweetening the meat. The outer thin-shell, as well as the inner bitter brown skin, is removed before eating. Removing the skin in its raw state is virtually impossible, but with patience, the outer shell can be removed from the raw nuts. It is much easier and recommended to blanch or cook fresh chestnuts before removal of the shell and skin. Shelled and cooked nuts can be covered and stored away in the refrigerator for a few days. If kept in the freezer, chestnuts can be frozen for up to nine months.
Simply roasted chestnuts can be made at home in about 30 minutes. They can also be candied, boiled, grilled, grounded into a flour, or pureed and sweetened to create delicious desserts. Because of the high starch content in chestnuts, they also work as substitutes for potatoes or pasta, as done in Europe. Americans mostly use them for stuffings and desserts, however. For example, one easy chestnut stuffing recipe calls for fresh chestnuts, butter, onion, seasonings, and more to mix into a seasoned turkey for the holidays or a traditional Sunday dinner.