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Nut (fruit)

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Revision as of 12:30, 1 February 2010 by The Thing That Should Not Be (talk | contribs) (Reverted edits by 82.109.65.217 (talk) to last revision by Loupeter (Report Mistake) (HG))(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff) For other uses, see Nut.
Hazelnuts from the Common Hazel
Chestnuts
A walnut and a walnut core having been removed from the outer pithy fruit. Walnuts are not true nuts.

Nut is a hard shelled fruit of some plants that has an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts. Nuts are an important source of nutrients for both humans and wildlife.

Nuts are a composite of the seed and the fruit, where the fruit does not open to release the seed. Most seeds come from fruits, and the seeds are free of the fruit, unlike nuts like hazelnuts, hickories, chestnuts and acorns, which have a stony fruit wall and originate from a compound ovary. Culinary usage of the term is less restrictive, and some nuts as defined in food preparation, like pistachios and Brazil nuts, are not nuts in a biological sense. Everyday common usage of the term often refers to any hard walled, edible kernel, as a nut.

The grouping of many similar dry seeds and fruits under the single generic name "nut" is not followed in many other languages, which have only individual names for each type.

Botanical definition

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 attached or fused with the ovary wall. Most nuts come from the pistils with inferior ovaries (see flower) and all are indehiscent (not opening at maturity). True nuts are produced, for example, by some plant families of the order Fagales.

Order Fagales

Culinary definition and uses

Korean Pine nuts — unshelled, and shell, above; shelled, below

A nut in cuisine is a much less restrictive category than a nut in botany, as the term is applied to many seeds that are not botanically true nuts. Any large, oily kernel found within a shell and used in food may be regarded as a nut. Pistachios are seeds enclosed in a tough fruit, which do not split open enough to release the seeds.

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. Nuts (or seeds generally) are also 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 late autumn, all of winter, and early spring.

Nuts used for food, whether true nut or not, are among the most common food allergens.

Some fruits and seeds that do not meet the botanical definition but are nuts in the culinary sense:

Nutritional benefits

A graph detailing the nutritional properties of nuts and oily seeds.

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 Omega 3 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.

One study found that people who eat nuts live two to three years longer than those who do not. However, this may be because people who eat nuts tend to eat less junk food.

Nuts contain the all important fatty acids, linoleic and linolenic acids, which are critical for growth, physical and mental development, healthy hair and skin, blood pressure control, immunological responses and blood clotting. In addition, the fats in nuts for the most part are unsaturated fats, particularly monounsaturated fats. This type does not elevate blood cholesterol levels like saturated fats.

Furthermore nuts supply one of the best natural sources of vitamins E, F, and G (docopherol, an antioxidant), and are rich in protein, folate, fiber, and essential minerals such as magnesium, phosphorus, potassium, copper, and selenium.

Other uses

The nut of the horse-chestnut tree (Aesculus species, especially Aesculus hippocastanum), is called a conker in the British Isles. Conkers are inedible because they contain toxic glucoside aesculin. They are used in a popular children's game, known as conkers, where the nuts are threaded onto a strong cord and then each contestant attempts to break his opponent's conker by hitting it with his own. Horse chestnuts are also popular slingshot ammunition.

A related species, Aesculus californica, was eaten by the Native Americans of California during famines after the toxic constituents were leached out.

See also

References

  1. Alasalvar, Cesarettin; Shahidi, Fereidoon. Tree Nuts: Composition, Phytochemicals, and Health Effects (Nutraceutical Science and Technology). CRC. p. 143. ISBN 978-0-8493-3735-2.
  2. Black, Michael H.; Halmer, Peter (2006). The encyclopedia of seeds: science, technology and uses. Wallingford, UK: CABI. p. 228. ISBN 978-0-85199-723-0.
  3. "Common Food Allergens". Food Allergy & Anaphylaxis Network. Retrieved 2007-06-24.
  4. David Mendosa (2002). "Revised International Table of Glycemic Index (GI) and Glycemic Load (GL) Values". Retrieved 2007-11-23. {{cite web}}: Cite has empty unknown parameter: |1= (help)
  5. "ABC News: The Places Where People Live Longest". URL accessed January 18, 2007.
  • John Harvey Kellogg, "Nuts May Save the Race." The Itinerary of Breakfast. New York: Funk & Wagnalls Company, 1920. 165–203.

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