Water-soluble plant dyes that are found in almost all higher plants and give the flowers and fruits the red, violet, blue or blue-black color. They belong to the group of phenols (Polyphenols), as well as the large group of dyes of over 6,500 species flavonoids, The name comes from the Greek terms anthos (blossom, flower) and kyáneos (dark blue). Anthocyanins are the ones glycosides (Sugar compounds) of the sugar-free anthocyanidins, the actual dye components. The attached sugar molecules (Glycone) cause the color pigments to be water-soluble. About 250 different anthocyanins are known. In the wine it is mainly the glycosides of cyanidin Delphinidine malvidine. peonidin and petunidine.
The colors of anthocyanins are strong from PH value dependent. In the acidic environment, the red color predominates, in the basic there are mainly blue and violet tones. Anthocyanins are sensitive to light and temperature and are susceptible to higher pH values - below 3 they are the most stable. At pH values between 6 and 7 they are present as flavenols and are rather blue, between 7 and 8 purple. From pH values above 8, the molecule is converted to a yellow chalcon. The anthocyanins of the grape form during the veraison, where the green grapes turn dark. In most varieties, the dyes are formed exclusively in the berry skin. Only with the Teinturiers (Dye grapes) is also a part of the dark flesh.
The colour of red wine differs depending on the proportions of anthocyanins present. Cyanidin and Delphinidin give a blue color. That in blue grapes Malvidin-3-glucoside, the most commonly represented with over 40%, causes deep red tones, which is why the red wines made from blue grapes ultimately appear predominantly red. However, the proportions of individual anthocyanins in the berries are specific to the grape variety. The smaller the berries, the more intense the coloring. This is because many small berries with often thick skins have a more pigmented skin surface than fewer, but larger berries. The color intensity is also from PH value dependent on the wine. An acidic wine with a very low pH is intensely bright red, an acid weak wine with a slightly higher pH has a darker color from purple to bluish. This phenomenon is evident in many plants, such as roses and also other flowers, the color of which is determined by the acidity of the soil.
oxidant have a decolorizing effect on anthocyanins. That's why too much sulfur dioxide cause the red color to fade in the wine. Some anthocyanins are converted into proanthocyanidins (tannin derivatives) by metabolic processes in the grape. In the bottle aging respectively. aging In a wine, anthocyanins also react with the tannins and are considered deep red depot (Sediment) failed. This causes the wine color to change and fade during the aging process. The red component decreases, while the yellow component increases relatively. The red wine turns brown and becomes lighter in color. Since each grape variety has a specific anthocyanin pattern, the color profile can also be used to identify grape varieties. This is done using chromatography and spectrometry of grapes or wine.
A specific anthocyanin derivative is malvidin-3,5-diglucoside, which is found primarily in wild American vines Vitis labrusca is included. The term "hybrid dye" or "direct carrier dye" is misleading, however, because unbredged and / or unrefined Labrusca vines also contain the dye. It gives the wine a typical orange-red color. In the varieties of the European species Vitis vinifera this substance is undetectable. Although it has no negative influence on the taste and is also harmless to health, it proves with its appearance that the grapes in question contain American genes or that a wine contains parts of a wine made from such grapes. May within the EU hybrids not used for wine production without shares in European genes (see under Quality wine-grape varieties ).
The INAO (Institut National des Appellations d'Origine) has a special one chromatographic Method (HPLC) for the detection of malvidin-3,5-diglucoside with a maximum value of 15 mg / l. However, the aim is to reduce the maximum to 2 mg / l for quality wines, but so far no agreement has been reached within the EU member states. In the new breed of fungal resistant varieties are resistant American vines have been used and thus Malvidin-3,5-diglucoside genes also come into the varieties. These are among others Cabernet Carol. Cabernet Cortis. Medina (1), monarch. regent and rondo, In the latter two varieties, the limit value of 200 to 300 mg / l is considerably exceeded. In Austria the quality wine test for awarding the State test number routinely tested for malvidin-3,5-diglucoside with a limit of 15 mg / l. See a list of all wine ingredients below total extract,