A walnut is the nut of any tree of the genus Juglans (Family Juglandaceae), particularly the Persian or English walnut, Juglans Regia. Technically a walnut is the seed of a drupe or drupaceous nut, and thus not a true botanical nut. It is used for food after being processed while green for pickled walnuts or after full ripening for its nutmeat. Nutmeat of the eastern black walnut from the Juglans nigra is less commercially available, as are butternut nutmeats from Juglans cinerea. The walnut is nutrient-dense with protein and essential fatty acids.
Walnut meats are available in two forms; in their shells or shelled. The meats can be as large as halves or any smaller portions that may happen during processing, candied or as an ingredient in other foodstuffs. Pickled walnuts that are the whole fruit can be savory or sweet depending on the preserving solution. Walnut butters can be homemade or purchased in both raw and roasted forms. All walnuts can be eaten on their own (raw, toasted or pickled) or as part of a mix such as muesli, or as an ingredient of a dish. For example, walnut soup and walnut pie are prepared using walnuts as a main ingredient. Walnut Whip, coffee and walnut cake, and pickled walnuts are more examples.
Walnut is the main ingredient of Fesenjan, a khoresh (stew) in Iranian cuisine. Walnuts are also popular in brownie recipes, as ice cream toppings, and walnut pieces are used as a garnish on some foods. Nocino is a liqueur made from unripe green walnuts steeped in alcohol with syrup added.
Walnut oil is available commercially and is chiefly used as a food ingredient particularly in salad dressings. It has a low smoke point, which limits its use for frying.
In 2014, worldwide production of walnuts (in shell) was 3.46 million tonnes, with China contributing 46% of the world total (table). Other major producers were (in the order of decreasing harvest): United States, Iran, Turkey and Mexico.
The average worldwide walnut yield was about 3.5 tonnes per hectare in 2014. Eastern European countries had the highest yield, with Slovenia and Romania each harvesting about 19 tonnes per hectare.
In 2014, the United States was the world’s largest exporter of walnuts, followed by Turkey. The Central Valley of California produces 99 percent of total United States commerce in English walnuts.
Walnuts without shells are 4% water, 15% protein, 65% fat, and 14% carbohydrates, including 7% dietary fiber (table).
In a 100 gram serving, walnuts provide 2,740 kilojoules (654 kcal) and rich content (more than 19% of the Daily Value or DV) of several dietary minerals, particularly manganese at 163% DV, and B vitamins (table).
While English walnuts are the most commonly consumed, their nutrient density and profile are generally similar to those of black walnuts.
Unlike most nuts that are high in monounsaturated fatty acids, walnut oil is composed largely of polyunsaturated fatty acids (72% of total fats), particularly alpha-linolenic acid (14%) and linoleic acid (58%), although it does contain oleic acid as 13% of total fats.