It seems difficult to talk about wine without giving its legal definition: "Product obtained exclusively by the total or partial alcoholic fermentation of fresh grapes, whether or not crushed, or of grape must, a living liquid, wine can be affected by diseases, it ages, it dies" (RIP 😭).
1) the seeds of the grape
Its role: It can be considered as the framework of the cluster. It constitutes the nourishing link between the grapes and the stump (elements taken from the soil) and between the grapes and the leaves, real laboratories involved in the formation of sugars (by photosynthesis).
Its constitution: While chewing a piece of stalk several sensations are felt:
° A bitter, unpleasant taste that dries the mouth; it is due to the presence of TANINS that can confer the wine of Astringency. Tannins are very important because they intervene in the quality and conservation.
° An acid flavour, due to the main organic acids it contains and that we will find in the wine (tartaric, malic and citric acids). These elements are also involved in the preservation of the wines and give them freshness.
° The fibrous matter that remains in the mouth is essentially made up of cellulose. The stalk also contains mineral matter (especially potassium salts).
The constitution of the wine is different depending on whether all or part of the stems were used during maceration. This applies only to red wines, as in principle there is no maceration for white wines. Some winemakers practice a light skin contact maceration on certain white grape varieties, to obtain a better aromatic intensity; this is what Americans call "skin contact".
2) The seeds
The seeds consists of 3 essential parts: the skin, the pulp and the seeds.
° The skin: It is covered with a waxy material: the bloom, which is the white deposit on the skin. It ensures impermeability and retains the yeasts brought by the wind and insects. The skin is very important in winemaking because it contains colouring matter and, for certain grape varieties, aromatic substances. The colouring matters are contained in the film: Anthocyanes for red wines and Flavones for whites. There are a few exceptions, the so-called "Cépages teinturiers". For the latter, which are very rare, the colouring matter is present in the pulp.
By pressing a bunch of red grapes between the hands, the juice obtained is colourless. At this moment, three possibilities can be considered:
1) To let the juice ferment alone, to obtain a white wine, as it is practiced in Champagne. By pressing a grape lightly in order to recover only the juice without transferring the pigments present in the skin, we obtain a white of blacks .
2) Let the juice and skins ferment together. After a certain time of maceration, the colour of the skin is transferred into the juice. Some farms are equipped to heat all or part of the harvest and obtain a better dissolution of the colouring matter (thermovinification).
3) Separate the liquid from the skins as soon as it reaches the colour of a rosé wine, then let it ferment on its own. In this case we obtain a rosé by "saignée de cuvée" or "rosé de saignée".
Aromatic substances: in certain grape varieties, the aromatic substances are located in the skins (Riesling, Muscat, etc.). The aromas are constant for each grape variety, but their intensity varies according to the vintage, the nature of the soil, etc.
3) The Pulp
The pulp or flesh is the most important part of the grape berry.
Composition: water 70 to 80%, sugars (mainly glucose and levulose) 100 to 300g per litre of must, organic acids, mineral salts, nitrogenous compounds (essential for the life of the yeasts, vitamins.
The importance of sugars: The sugar content is very low in green grapes. It increases after venison (change of colour of the grapes). At harvest time, the increase can be 4 to 5g of sugar per day. You should know that it takes on average 17g of sugar to obtain an alcoholic degree, it is easy to determine the date of the harvest.
During alcoholic fermentation the sugar contained in the must is essentially transformed into ethyl alcohol (or ethanol), the degree of a wine depends therefore on the sugar content of the grapes. This richness is not constant from one year to another, it is the sunshine, which favours or not photosynthesis.
Acids are as important as sugars. Their content varies according to the grape varieties, the region, the year and maturity. Grapes essentially contain the following acids: tartaric acid, malic acid and citric acid. If an excess of acidity can be a defect, a lack of acidity is also a defect.
foot treading in the 15th century
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