Anthocyanin to tannin ratio

Impact Of Anthocyanin To Tannin Ratio On Wine Pigment Composition... 

In addition to the molecnlar strnctnre, the tan-nin/anthocyanin ratio also affects wine development. Color has been observed to change rapidly due to anthocyanin breakdown reactions when the medinm has a low tannin content (molar ratio T/A tannin polymerization reactions when the tannin concentration is much higher than the anthocyanin content (molar ratio T j A < 4). If a wine is to develop harmoniously, this ratio should be between 1 and 4, i.e. 500 mg of anthocyanins and 1-3 g of tannins per liter of wine. 

In stabilization reactions, several mechanisms lead to the formation of tannin-anthocyanin combinations, depending not only on the conditions in the medium (temperature, oxidation) but also on the type of tannins and the tannin/anthocyanin ratio. The color of the new pigments ranges from mauve to orange and is more intense at the pH of wine than that of free anthocyanins. It depends relatively little on the SO2 content of the medium. These molecules are not detected by chemical anthocyanin assays and are only very partially taken into account in the results. 

Rapid oxidation (Section 6.3.3) has an effect on all these molecules if they are not protected by a sufficient quantity of tannins. The molar ratio T/A must be at least 2, otherwise wine behaves like a pure authocyanin solution. There is a much lower risk of breakdown reactions under controlled oxidation conditions as malvidin, the main anthocyanin in wine, is not dihydroxylated and, consequently, is not very sensitive to slow oxidation. 

A wine s behavior dnring aging therefore depends on a whole series of factors related to its composition. These inclnde not only phenol content, but also the type of tannins and their structures, as well as the tannin/anthocyanin ratio and the polysaccharide concentration. Fnrthermore, the wine s initial composition changes dnring aging, developing complex new strnctnres likely to slow down the process of stripping. 

The tannin/anthocyanin ratio permits the two winemaking methods (direct pressing and drawing off) to be differentiated. This ratio diminishes as the maceration time increases and it is higher when the grapes are directly pressed. 

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