Chestnut flour is a nut flour made from ground European chestnuts, and has a distinctive texture and scent. This product has a relatively short shelf life, and is usually sold in the autumn and winter by international groceries and health food stores. The best chestnut flour is a light yellow to tan color, slightly clumpy in texture, and smells strongly of roasted chestnuts. This food should never have a sour odor or seem dusty, dry, or bland. Chestnut flour is associated with traditional baking in some parts of Italy, but, as this flour contains no gluten, it is safe for use by those with Celiac disease and others with gluten intolerance.
Most chestnut flour is made by grinding whole roasted chestnuts into a fine powder, which smells strongly of chestnuts and tastes slightly sweet, nutty, and oily. The fat content of this flour means that it spoils quickly, making it a seasonal product in many markets. You can purchase chestnut flour in the fall and winter at Italian grocery stores, specialty baking shops, and health food stores. It is sometimes available outside of the season if refrigerated or frozen, and should always be kept chilled to extend its shelf life.
You should look for a soft, even powder with a light yellow to light brown color and a very strong nutty scent and flavor. The oil in the flour may cause it to form soft clumps in the bag, but these should be easy to break apart with your fingers, even through the package. Never buy flour that doesn't have a detectable scent or which smells tart or sour; these characteristics indicate a stale or spoiled product. Sour-smelling chestnut flour also has a sour taste, which cannot be covered by cooking or flavorings.
This flour originated as a substitute for wheat flour in parts of northern Italy, where chestnuts were more readily available to the poor than grain. Chestnut flour works both in sweet and savory dishes, and may be accompanied by dried fruit, other nuts, or chocolate, as well as herbs or cheese. It is traditionally mixed with some wheat flour for use in cakes, pastas, and crepes, but can be used on its own by people who cannot eat gluten. As chestnut flour contains no gluten of its own, it does not rise in cakes or other baked goods without the addition of guar gum or other strengthening ingredients.