From Wikipedia, the free encyclopedia
A nut can be both a seed and a fruit.
A nut in botany is a simple dry fruit with one seed (rarely two) in which the ovary wall becomes very hard (stony or woody) at maturity, and where the seed remains unattached or unfused with the ovary wall. Most nuts come from pistils with inferior ovaries (see flower) and all are indehiscent (not opening at maturity). True nuts are produced - for example - by some plants-families of the order Fagales. Note that not all true nuts are edible; some (e.g. birch, alder, hornbeam, wingnut) are too small to be worth eating. Others, like the tanoak (Lithocarpus densiflorus), are bitter due to tannins and require extensive leaching before they are edible.
- Order Fagales
- Family Juglandaceae
- Walnut, Butternut (Juglans)
- Hickory, Pecan (Carya)
- Wingnut (Pterocarya)
- Family Fagaceae
- Chestnut (Castanea)
- Beech (Fagus)
- Oak (Quercus)
- Stone-oak, Tanoak (Lithocarpus)
- Family Betulaceae
- Alder (Alnus)
- Birch (Betula)
- Hazel, Filbert (Corylus)
- Hornbeam (Carpinus)
Culinary definition and uses
A nut in cuisine is a much less restrictive category than a nut in botany, the term being applied (or misapplied, depending upon the viewpoint) to many seeds that are not true nuts. Any large, oily kernel found within a shell and used in food may be regarded as a nut. Because nuts generally have a high oil content, they are a highly prized food and energy source. A large number of seeds are edible by humans and used in cooking, eaten raw, sprouted, or roasted as a snack food, or pressed for oil that is used in cookery and cosmetics. By the same token, nuts (or seeds generally) are a significant source of nutrition for wildlife. This is particularly true in temperate climates where animals such as jays and squirrels store acorns and other nuts during the autumn to keep them from starving during the winter and early spring.
Some fruits and seeds that are nuts in the culinary sense but not in the botanical sense:
- Almond is the edible seed of a drupe - the leathery "flesh" is removed at harvest.
- Brazil nut is the seed from a capsule.
- Candlenut (used for oil) is a seed.
- Cashew nut is a seed.
- Coconut is a dry, fibrous drupe.
- Corn nut is a roasted or deep fried maize seed.
- Horse-chestnut is an inedible capsule.
- Macadamia nut is a creamy white kernel (Macadamia integrifolia).
- Peanut is a legume and a seed.
- Pine nut is the seed of several species of pine (coniferous trees).
- Pistachio nut is the seed of a thin-shelled drupe.
See also: List of edible seeds
Nuts versus seeds
As mentioned previously, the term nut is sometimes used on seeds, but nuts and seeds are not the same thing. A nut is a seed, but not all seeds are nuts. A seed comes from fruit and can be removed from the fruit. A nut is a compound ovary that is both the seed and the fruit, which cannot be separated.
Besides seeds, others that are mislabeled as nuts include legume (separate hard seeds), drupe (contains endocarp which contains seeds) and capsule (dried fruit that splits to release seeds).
Allergy to nuts is a relatively common and often very serious problem. For people with nut allergy, exposure to surprisingly small amounts of nut fragments (e.g. minor cross-contamination of otherwise nut-free products in a food processing factory) can cause fatal anaphylactic shock.
Allergy to peanuts is the most common; some evidence suggests that some peanut allergies may be related to the use of peanuts in baby foods; if given to very young children who are not yet able to digest all the components of peanuts fully, the body will then react against those components. As the peanut is a member of the pea family unrelated to other nuts, individuals with allergies to peanuts may not be allergic to other nuts, and those with allergies to other nuts may not be allergic to peanuts. A common term applied to nuts, used to distinguish peanuts from nuts, is "tree nuts".
Several epidemiological studies have revealed that people who consume nuts regularly are less likely to suffer from coronary heart disease. Recent clinical trials have found that consumption of various nuts such as almonds and walnuts can lower serum LDL cholesterol concentrations. Although nuts contain various substances thought to possess cardioprotective effects, scientists believe that their fatty acid profile is at least in part responsible for the hypolipidemic response observed in clinical trials.
In addition to possessing cardioprotective effects, nuts generally have a very low glycemic index (GI). Consequently, dietitians frequently recommend nuts be included in diets prescribed for patients with insulin resistance problems such as diabetes mellitus type 2.
- See also Chart of nutritional properties of nuts and oily seeds
The "nut" of the horse-chestnut, (Aesculus hippocastanum), is also known as a conker. Conkers are inedible but are collected and used in an old children's game, also known as conkers, in which a nut is threaded onto a strong cord and then each child attempts to break their opponent's conker by hitting it with their own. A related species, Aesculus californica, was formerly eaten by the Native Americans of California in times of famine. It must be leached to remove poisonous constituents before eating.
- Photos of some nuts
- Nut crackers
- Nutra-Smart.net Health Benefits of Nuts
- Linus Pauling Micronutrient Information Centre Nuts
- American Journal of Clinical Nutrition Nuts and their bioactive constituents: effects on serum lipids and other factors that affect disease risk