The grape varieties are numerous, those of interest for human consumption are about ten and mainly belong to two species, the Vitis Vinifera of European origin and the Vitis Labrusca which belongs to the group of American vines.
In Italy, the varieties cultivated for food purposes, the so-called table grapes, mainly belong to the Italia, Vittoria and Regina varieties for the white grapes and Moscato d'Amburgo, Red Globe and Rosada for the red ones. From a nutritional point of view, table grapes, like all fruits, are characterized by a very high water content, over 80% of the edible part, and by the sugar content, about 15% by weight. Unlike other fruits, the fiber content is relatively low, equal to about 1,5% by weight. Completely negligible from a nutritional point of view are the contents of lipids and proteins. It is interesting to note how the sugars present in the pulp of ripe grapes are mainly monosaccharides of glucose and fructose, this characteristic makes grapes an even sweeter food than the carbohydrate content would suggest. From an energy point of view, grapes provide about 61 kcal/100g, a value that makes them one of the most energy-rich fruits when compared with those most commonly consumed in Italy such as peaches, plums, apricots, apples, pears or melons .
As regards the average content of micronutrients in table grapes, the very low sodium content and a moderate potassium content should be underlined. Much more scarce is the presence of other minerals and vitamins. Grapes also have an interesting content of total polyphenols concentrated, if we refer to the edible part, in the skin, which correspond to about 300 mgGAE*/100g of grapes.
The 'annoying' pips are also important
A separate note should be reserved for grape seeds, the often hated grape seeds, which are actually an interesting source of polyunsaturated fatty acids of the omega-6 series. In fact, grape seed oil is a delicate oil with a light color and a sweet and fruity taste which is characterized by the high content of linoleic acid, about 67%, and by the low content of saturated fatty acids, about 9%. Historically, its main uses are in the cosmetic and chemical industries for the production of paints. Its use in the kitchen is still modest although recently chefs and bloggers are proposing its use in some interesting recipes.
Throughout history, man soon understood that perhaps the best thing to do with grapes was wine. Testimonies of wine production date back to very ancient times and are located in Mesopotamia and the Far East. In Europe the culture of wine merges with classical mythology and reaches its peak with the Christian religion in which wine comes to represent the blood of Christ. In art, the quotations could be very numerous, one of all, a work by Michelangelo, "the drunkenness of Noah" scene from Genesis which is located in the Sistine Chapel.
From a nutritional point of view, the wine is characterized by the ethanol content, a product of the fermentation to which the grape sugars are subjected during winemaking. Although alcohol is not considered a nutrient, it provides plenty of energy, 7kcal/g. However, not everyone knows how to calculate the kcal starting from the alcohol content of a wine which expresses the alcohol content in ml/100ml of drink. To do this it is necessary to take into account the density of the alcohol to pass from the alcohol content to the grams and kcal contained.
During the vinification processes, particularly as regards red wines, numerous phenolic compounds are extracted from the pomace which will concentrate in the wines until they reach truly significant quantities, between 1 and 5 g/L. Another phenomenon, which contributes to enriching the wines with further phenolic compounds, is represented by possible passages in wooden barrels which release further compounds. The main phenols present in wines are catechins, anthocyanidins, phenolic acids, resveratrol and for the most part, about 60-70% of the total, from polymeric polyphenols such as condensed tannins or proanthocyanidins responsible for the characteristic astringency of red wines due to the ability to precipitate proteins rich in proline such as salivary proteins.
Polyphenols: the French paradox, red wine against cardiovascular diseases
There are numerous scientific publications which over the years have demonstrated the protective action of wine polyphenols against cardiovascular diseases, diabetes, metabolic syndrome, inflammatory states and oxidative stress. These observations led to the development of the concept known as the "French Paradox", to explain the phenomenon according to which the French populations, precisely thanks to the consumption of red wines, did not have a high incidence of cardiovascular pathologies despite the high consumption of saturated fats (butter ) in the diet. Of all the polyphenols in wine, the one that has always enjoyed the greatest popularity is certainly resveratrol, a molecule which, with studies conducted mainly in vitro and in animal models, has demonstrated interesting properties related to the maintenance of vascular, antioxidant, anti-aging functions . However, resveratrol represents less than 1% of all polyphenols in red wines, therefore, currently, the beneficial properties of wine polyphenols are attributed to the overall blend of polyphenols themselves and their metabolites.
More controversial is the effect of ethanol. On the one hand, abundant scientific literature recognizes that low doses of ethanol have a synergistic effect with that of polyphenols in reducing the relative risk of cardiovascular mortality, on the other, very recent studies believe these benefits are not sufficient to compensate for the increased risk of cancer due to ethanol consumption.
A dangerous fad, binge drinking
That ethanol was a carcinogen is certainly not new, the International Agency for Research on Cancer (IARC) included it in "Group 1", which includes all known carcinogenic substances for humans, already many years does exactly as it happened more recently for processed and processed meats. This does not mean that, although some authors propose that the only dose of alcohol without risk is the zero dose, alcoholic beverages, as well as processed meats, should be banned from our tables. The relative risk grows with the increase in exposure and the food guidelines today contemplate, among healthy eating habits, although they do not encourage it, a moderate consumption of alcoholic beverages, better if low-proof. A valid example of data collected to support of a low and moderate consumption of wine or beer is provided by the EPIC-Norfolk Prospective Population Study, published in 2008, in which the healthy behaviors capable of improving life expectancy include a consumption of alcoholic beverages between 1 and 14 units of alcohol per week.
To date, therefore, the heart of the problem remains linked to quantity, it is easy to talk about moderate consumption, understood as consumption between 1 and 2 units of alcohol per day (8-16 g ethanol/day**), much more difficult is to seriously educate at such moderate consumption. While on the one hand, the number of people who consume alcohol daily is decreasing, on the other, the number of people, mainly young people, who consume more than 6 units of alcohol in the same day, is increasing, a phenomenon known as binge drinking. drinking, exposing themselves to very serious health risks.
