Anthocyanins are classified by the position of hydroxyl and methyl groups on the second phenyl ring. Based on this, anthocyanins are separated into five groups; cyanins, petunins, peonins, malvins and delphinins.
The presence and concentration of each of the five groups of anthocyanins is varietal specific and changes with changing environmental conditions and viticultural practices. The proportion of five classes has a huge impact on the color and color stability in a wine.
Color and color stability are largely affected by the number of hydroxyl and methyl groups. The number of free hydroxyl groups is directly related to blueness; the number of methyl groups is directly related to redness. An example of this phenomenon is malvin. It is the primary anthocyanin in red grapes, and not surprisingly, it has the greatest degree of methylation and thus the reddest color.