The grape is the fruit of the vine (Vitis). The grape from the cultivated vine Vitis vinifera is one of the most cultivated fruits in the world, with 68 million tonnes produced in 2010, behind citrus fruits (124 million), bananas (102 million) and apples (70 million). It is in the form of clusters composed of many grains, which are botanically berries, small and light in color, for the white grape (greenish, yellowish, golden yellow).
It is mainly used for the production of wine from its fermented juice (we speak in this case of wine grapes), but it is also consumed as fruit, either fresh, table grapes, or dry, raisins which is mainly used in baking or cooking. We also consume grape juice. Berries also extract grape seed oil.
The main cultivated species are:
Vitis vinifera, native to south-eastern Europe and the Near East and the Caucasus, from which all the great grape varieties for wine and table grapes originate.
Vitis labrusca, native to North America, is used mainly as table grapes and a little bit for wine. During the attack on European vines by Phylloxera, European grape varieties were saved by grafting them on strains of Vitis labrusca.
Very incidentally, Vitis coignetiae is cultivated in Korea for its table grapes and for making wine. In China, Vitis amurensis is cultivated in the northeast (4000 ha in Jilin) for the production of wine.
Composition and nutritional value
Its high sugar content can cause sugar to crystallize over time. To decristallize a grape, simply immerse it in a liquid (alcohol, fruit juice or boiling water), until the sugar dissolves.
Rich in vitamins A, B and C, the grape contains many trace elements in a balance which is perfectly assimilated by the body. Each grape is covered with bloom rich in yeast.
It is a fairly energetic fruit with 278 kJ (= 65.6 kcal) per 100 g.
Biological propertiesEpidemiological studies on the beneficial effects of active grape compounds cannot be done directly because fresh grapes do not keep well and are not usually consumed regularly.
In the grape berry, most of the polyphenols (94%) are concentrated in the skin and the seeds. During red wine making, keeping the wort in contact with the skins and seeds (maceration) makes it possible to extract "the best of the grapes". The development of white wines or grape juice being done without this extraction operation, we can not hope to find in them all the phenolic potential of the grape.
A famous study by Renaud and Lorgeril (1992) has shown that a high consumption of saturated fat in Toulouse is abnormally associated with a low mortality rate from coronary heart disease. The authors proposed to explain this "French paradox" by the French habit of regularly drinking wine.
Several mechanisms have been proposed to explain the protective effect of grape polyphenols against cardiovascular disease:
- antioxidant activity,
- reducing LDL oxidation because we know that the oxidation of LDL-c lipoproteins (bad cholesterol) is an important step in the development of atherosclerosis. An intervention study18 of 31 people, who were given an alcohol-free red wine extract for two weeks, showed inhibition of LDL oxidation ex vivo. The efficacy of grape extracts on the atheromatous lesions of mice has also been shown to be effective19. The mice who took the grape polyphenol supplement for 10 weeks saw a 41% regression in the area of their atheromatous lesion (compared to the control or placebo mice). A randomized double-blind study20 in 40 patients with hypercholesterolemia showed that the reduction in the level of LDL-c and cholesterol was only obtained in patients consuming grape seed proanthocyanidols, if they were accompanied of taking chromium bound to niacin.
- inhibition of platelet aggregation. When platelet aggregation occurs at the level of an atheroma plaque, it can cause a blood clot (thrombus) that can clog brain vessels. A study of 10 people who were given various fruit juices for a week, showed21 that red grape juice significantly inhibited platelet aggregation unlike grapefruit or orange juice. This grape juice contained much more phenolic compounds than the other N 5 juices.
- modulation of the inflammatory cascade,
- improving endothelial function