Grape

A grape is the non-climacteric fruit that grows on the perennial and deciduous woody vines of the genus Vitis. Grapes can be eaten raw or used for making jam, juice, jelly, vinegar, wine, grape seed extracts and grape seed oil. Grapes are also used in some kinds of candy.

Description

Grapes grow in clusters of 6 to 300, and can be crimson, black, dark blue, yellow, green and pink. "White" grapes are actually green in color, and are evolutionarily derived from the red grape. Mutations in two regulatory genes of white grapes turn off production of anthocyanins which are responsible for the color of red grapes.^[1] Anthocyanins and other pigment chemicals of the larger family of polyphenols in red grapes are responsible for the varying shades of purple in red wines.^[2][3]

Grapevines

Main article: Vitis

Most grapes come from cultivars of Vitis vinifera, the European grapevine native to the Mediterranean and Central Asia. Minor amounts of fruit and wine come from American and Asian species such as:

• Vitis labrusca, the North American table and grape juice grapevines (including the concord cultivar), sometimes used for wine. Native to the Eastern United States and Canada.
• Vitis riparia, a wild vine of North America, sometimes used for winemaking and for jam. Native to the entire Eastern U.S. and north to Quebec.
• Vitis rotundifolia, the muscadines, used for jams and wine. Native to the Southeastern United States from Delaware to the Gulf of Mexico.
• Vitis amurensis Most important Asian species.

Distribution and production

Grape production in 2005

According to the Food and Agriculture Organization (FAO), 75,866 square kilometres of the world are dedicated to grapes. Approximately 71% of world grape production is used for wine, 27% as fresh fruit, and 2% as dried fruit. A portion of grape production goes to producing grape juice to be reconstituted for fruits canned "with no added sugar" and "100% natural". The area dedicated to vineyards is increasing by about 2% per year.

The following table of top wine-producers shows the corresponding areas dedicated to grapes for wine making:

Top Ten Grapes Producers — 11 June 2008
Country	Production (Tonnes)	Footnote
Italy	8519418
France	6500000	F
People's Republic of China	6250000	F
United States	6105080
Spain	6013000
Turkey	3923040
Iran	3000000	F
Argentina	2900000	F
Chile	2350000	F
India	1667700
World	7501872	A
No symbol = official figure, P = official figure, F = FAO estimate, * = Unofficial/Semi-official/mirror data, C = Calculated figure A = Aggregate(may include official, semi-official or estimates); Source: Food And Agricultural Organization of United Nations: Economic And Social Department: The Statistical Devision

Seedless grapes

Seedlessness is a highly desirable subjective quality in table grape selection, and seedless cultivars now make up the overwhelming majority of table grape plantings. Because grapevines are vegetatively propagated by cuttings, the lack of seeds does not present a problem for reproduction. It is, however, an issue for breeders, who must either use a seeded variety as the female parent or rescue embryos early in development using tissue culture techniques.

There are several sources of the seedlessness trait, and essentially all commercial cultivators get it from one of three sources: Thompson Seedless, Russian Seedless, and Black Monukka, all being cultivars of Vitis vinifera. Numerous seedless cultivars, such as Einset Seedless, Reliance and Venus, have been specifically cultivated for hardiness and quality in the relatively cold climates of north-eastern United States and southern Ontario.^[4] Bright green and elongated or round, the popular Sugraone grape offers a light, sweet flavor and distinctive crunch.

Contrary to the improved eating quality of seedlessness is the loss of potential health benefits provided by the enriched phytochemical content of grape seeds (see Health claims).^[5][6]

Raisins, currants, and sultanas

See also: Dried vine fruit

Raisins

In most of Europe, dried grapes are universally referred to as 'raisins' or the local equivalent. In the UK, three different varieties are recognized, forcing the EU to use the term "Dried vine fruit" in official documents.

A raisin is any dried grape. While raisin is a French loanword, the word in French refers to the fresh fruit; grappe (whence the English grape is derived) refers to the bunch (as in une grappe de raisins).

A currant is a dried Zante grape, the name being a corruption of the French raisin de Corinthe (Corinth grape). Note also that currant has come to refer also to the blackcurrant and redcurrant, two berries completely unrelated to grapes.

A sultana was originally a raisin made from a specific type of grape of Turkish origin, but the word is now applied to raisins made from common grapes and chemically treated to resemble the traditional sultana.

Health claims

Main articles: French Paradox and Resveratrol

French Paradox

Comparing diets among western countries, researchers have discovered that although the French tend to eat higher levels of animal fat, surprisingly the incidence of heart disease remains low in France, a phenomenon named the French Paradox and thought to occur from protective benefits of regularly consuming red wine. Apart from potential benefits of alcohol itself, including reduced platelet aggregation and vasodilation,^[7] polyphenols (e.g., resveratrol) mainly in the grape skin provide other suspected health benefits, such as:^[8]

• alteration of molecular mechanisms in blood vessels, reducing susceptibility to vascular damage
• decreased activity of angiotensin, a systemic hormone causing blood vessel constriction that would elevate blood pressure
• increased production of the vasodilator hormone, nitric oxide (endothelium-derived relaxing factor)

Although adoption of wine consumption is not recommended by some health authorities,^[9] a significant volume of research indicates moderate consumption, such as one glass of red wine a day for women and two for men, may confer health benefits.^[10][11][12] Emerging evidence is that wine polyphenols like resveratrol^[13] provide physiological benefit whereas alcohol itself may have protective effects on the cardiovascular system.^[14]

According to a Cancer Institute study, those who drank two standard alcoholic drinks per day increased the risk of mouth cancer by 75 per cent.^[15]

Resveratrol

Grape phytochemicals such as resveratrol, a polyphenol antioxidant, have been positively linked to inhibiting cancer, heart disease, degenerative nerve disease, viral infections and mechanisms of Alzheimer's disease.^[16][17]

Protection of the genome through antioxidant actions may be a general function of resveratrol.^[18] In laboratory studies, resveratrol bears a significant transcriptional overlap with the beneficial effects of calorie restriction in heart, skeletal muscle and brain. Both dietary interventions inhibit gene expression associated with heart and skeletal muscle aging, and prevent age-related heart failure.^[19]

Resveratrol is the subject of several human clinical trials,^[20] among which the most advanced is a one year dietary regimen in a Phase III study of elderly patients with Alzheimer's disease.^[21]

Synthesized by many plants, resveratrol apparently serves antifungal and other defensive properties. Dietary resveratrol has been shown to modulate the metabolism of lipids and to inhibit oxidation of low-density lipoproteins and aggregation of platelets.^[22]

Resveratrol is found in wide amounts among grape varieties, primarily in their skins and seeds which, in muscadine grapes, have about one hundred times higher concentration than pulp.^[23] Fresh grape skin contains about 50 to 100 micrograms of resveratrol per gram.^[24]

Anthocyanins and other phenolics

Anthocyanins tend to be the main polyphenolics in red grapes whereas flavan-3-ols (e.g., catechins) are the more abundant phenolic in white varieties.^[25] Total phenolic content, an index of dietary antioxidant strength, is higher in red varieties due almost entirely to anthocyanin density in red grape skin compared to absence of anthocyanins in white grape skin.^[25] It is these anthocyanins that are attracting the efforts of scientists to define their properties for human health.^[26] Phenolic content of grape skin varies with cultivar, soil composition, climate, geographic origin, and cultivation practices or exposure to diseases, such as fungal infections.

Red wine offers health benefits more so than white because many beneficial compounds are present in grape skin, and only red wine is fermented with skins. The amount of fermentation time a wine spends in contact with grape skins is an important determinant of its resveratrol content.[7] Ordinary non-muscadine red wine contains between 0.2 and 5.8 mg/L,^[27] depending on the grape variety, because it is fermented with the skins, allowing the wine to absorb the resveratrol. By contrast, a white wine contains lower phenolic contents because it is fermented after removal of skins.

Wines produced from muscadine grapes may contain more than 40 mg/L, an exceptional phenolic content.^[28][23] In muscadine skins, ellagic acid, myricetin, quercetin, kaempferol, and trans-resveratrol are major phenolics.^[29] Contrary to previous results, ellagic acid and not resveratrol is the major phenolic in muscadine grapes.

Seed constituents

Since the 1980s, biochemical and medical studies have demonstrated significant antioxidant properties of grape seed oligomeric proanthocyanidins.^[30] Together with tannins, polyphenols and polyunsaturated fatty acids, these seed constituents display inhibitory activities against several experimental disease models, including cancer, heart failure and other disorders of oxidative stress.^[31][32]

Grape seed oil from crushed seeds is used in cosmeceuticals and skincare products for many perceived health benefits. Grape seed oil is notable for its high contents of tocopherols (vitamin E), phytosterols, and polyunsaturated fatty acids such as linoleic acid, oleic acid and alpha-linolenic acid.^[33][34][35]

Concord grape juice

Commercial juice products from Concord grapes have been applied in medical research studies, showing potential benefits against the onset stage of cancer,^[36] platelet aggregation and other risk factors of atherosclerosis,^[37] loss of physical performance and mental acuity during aging^[38] and hypertension in humans.^[39]

Gallery

See also

• List of grape varieties
• Annual growth cycle of grapevines

Sources

Footnotes

External links

• Taxonomic listings for Vitis genus, US Department of Agriculture, Germplasm Resources Information Network
• Wild Grapes
• Major wine varieties
• SAFECROP - Proceedings of the 5th International Workshop on Grapevine Downy and Powdery Mildew
• World's Healthiest Foods, in-depth nutrient profile for grapes
• Information on virus diseases of wine grapes