page_title: White wine
section_title: The grape berry
hierarchical_section_title: White wine / Components of the grape and the must / The grape berry
caption_attribution_description: Français&#160;: Raisin de cuve (destiné à la vinification). Jus blanc et pellicule coloréeEnglish: Dark-skinned grapes intended for wine production. The colour is in the grape skins while the juice is white.
context_page_description: White wine is a wine that is fermented without skin contact. The colour can be straw-yellow, yellow-green, or yellow-gold. It is produced by the alcoholic fermentation of the non-coloured pulp of grapes, which may have a skin of any colour. White wine has existed for at least 2500 years.
  The wide variety of white wines comes from the large number of varieties, methods of winemaking, and ratios of residual sugar. White wine is mainly from "white" grapes, which are green or yellow in colour, such as the Chardonnay, Sauvignon blanc, and Riesling. Some white wine is also made from grapes with coloured skin, provided that the obtained wort is not stained. Pinot noir, for example, is commonly used to produce champagne.
  Among the many types of white wine, dry white wine is the most common. More or less aromatic and tangy, it is derived from the complete fermentation of the wort. Sweet wines, on the other hand, are produced by interrupting the fermentation before all the grape sugars are converted into alcohol; this is called Mutage or fortification. The methods of enriching wort with sugar are multiple: on-ripening on the vine, passerillage, or the use of noble rot.
context_section_description: The grape berry is made of skin, flesh (or pulp), and seeds. The seeds are hard and are 2 to 5% by weight of the berry. The seeds contain 25-45% water, 34-36% carbohydrates, 13-20% fat (the grape seed oil), 4-6% tannins, 4-6.5% protein, 2-4% minerals, and 1% fatty acids. Their contribution in white wine is zero since they are removed in the pressing, in addition, the pressure is insufficient to extract anything from the seed.
  The skin is 6-12% by weight of the grape. It is coated on the surface with Pruinescence, a waxy coating that gives a matte finish to the colour of the grape and contains the yeast responsible for fermentation. The grape skin also contains volatile compounds in its deeper layers. These are responsible for the aroma of the grape and for the molecules that become the aroma of wine during fermentation: they are the "aroma precursors". In red grapes the film also contains anthocyanins or coloured matter which is from bright to purplish red. To produce white wine from red grapes it is necessary not to macerate the grapes, nor to press too hard on the harvest to avoid the dissolving of the anthocyanins in the grape juice. The skin contains a lot of cellulose, insoluble pectin and proteins, and organic acids: citric, malic, and tartaric acids. The skin of the Sauvignon blanc B grape has a pH of about 4.15. It also contains between 2 and 3% tannins.
  The flesh of the grape is the most important part – it is between 75 and 85% of the weight of the grape. It consists of large polygonal cells which are very thin-walled. With a low pressure the cells leak their contents: the wort. The flesh of the grape contains mainly water. The organic components are fermentable sugars (between 170-230 grams for a dry wine and between 200 and 300 grams per litre or even more for Fortified wines) and organic acids, especially malic acid and tartaric acid. Acids occur in larger amounts in the centre of the berry while the sugars are in greater proportion at the periphery. This heterogeneity in the distribution of sugars, acids, and inorganic compounds in the berry is used during pressing, especially in Champagne pressing. This process separates them as it happens and uses them to measure the progress of the "vintage", the first and second tailles, and finally the rebêches of insufficient quality to be made into AOC wine.
  The flesh is the major element of the wine, as it is the part that contains the highest proportion of liquid. The flavours are much less present than in the skin.
caption: Section of a grape berry with white juice and coloured skin.
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