Water-soluble plant pigments, which are found in almost all higher plants and give the flowers and fruits the red, purple, blue or blue-black color. They belong to the group of phenols (Polyphenols), as well as the large over 6,500 species of dye group flavonoids, The name derives from the Greek terms anthos (flower, flower) and kyáneos (dark blue). Anthocyanins are the glycosides (Sugar compounds) of the sugar-free anthocyanidins, the actual dye components. The attached sugar molecules (glycones) cause the water solubility of the color pigments. There are about 250 different anthocyanins known. In wine, it is mainly the glycosides of cyanidin, Delphinidin, malvidine. peonidin and petunidin.
The colors of anthocyanins are strong of PH value dependent. In the acidic environment the red color prevails, in the basic one are mainly blue and violet tones. Anthocyanins are light- and temperature-sensitive and prone to higher pH levels - below 3 they are the most stable. At pHs between 6 and 7 they are flavenols and are more blue, between 7 and 8 purple. From pH values above 8, the molecule is converted to a yellow chalcone. The anthocyanins of the grape form during the veraison in which the green grapes turn dark. The dyes are formed in most varieties only in the berry skin. Only with the Teinturiers (Dyeing grapes) is also part of the then dark pulp.
The colour of red wine is different depending on the proportions of available anthocyanins. Cyanidin and delphinidin give a color that goes into the blue area. That in blue grapes with more than 40% most commonly represented malvidin-3-glucoside causes deep red shades, which is why the red wines pressed from blue grapes ultimately appear predominantly red. However, the proportions of individual anthocyanins in the berries are specific to the variety. The smaller the berries, the more intense the coloring. This is because many small berries, often with a thick shell, have more pigmented shell surface overall than fewer but larger berries. The color intensity is also from the PH value depending on the wine. A very acidic wine with a very low pH is intensely bright red, while a slightly acidic 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 other flowers whose flower color is determined by the acidity of the soil.
oxidant have a decolorizing effect on anthocyanins. That's why too much sulfur dioxide cause a fading of the red color in the wine. Some anthocyanins are converted by metabolic processes in the grape into proanthocyanidins (tannin derivatives). In the bottle aging respectively. aging Anthocyanins also react with the tannins and are considered deep red depot (Sediment) precipitated. This thus causes the change and fading of the wine color during the aging process. The proportion of red decreases while it increases proportion of yellow relative. The red wine turns brownish and becomes lighter. Since each grape has a specific anthocyanin pattern, the dye profile can be used in part for grape identification. This is done by means of chromatography and spectrometry of grapes or wine.
A specific anthocyanin derivative is malvidin-3,5-diglucoside, which is found mainly in the American wild grape Vitis labrusca is included. However, the term "hybrid dye" or "direct carrier dye" is misleading because non-crossed and / or unrefined Labrusca vines also possess 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, but proves with its occurrence that the grapes in question contain American genes or a wine contains portions of a wine pressed from such grapes. Within the EU may hybrids without shares in European genes are not used for wine production (see below Quality wine-grape varieties ).
The INAO (Institut National des Appellations d'Origine) has a special chromatographic Method (HPLC) for the detection of malvidin-3,5-diglucoside with a maximum limit of 15 mg / l. However, the aim is to reduce it to a maximum of 2 mg / l for quality wines, but so far no agreement has been reached within the EU member states. In the new breed of fungus resistant varieties are resistant American vines used and thus also malvidin-3,5-diglucoside genes enters the varieties. Among others, these are Cabernet Carol. Cabernet Cortis. Medina (1), monarch. regent and rondo, For the latter two varieties, the limit is considerably exceeded at 200 to 300 mg / l. In Austria, since 2009, the quality wine examination for the award of the State test number routinely tested for malvidin-3,5-diglucoside to the limit of 15 mg / l. See a list of all wine ingredients below total extract,