Do white grapes really exist?

Anthocyanins are natural coloured pigments representing part of the protective mechanism of many plants, including Vitis vinifera L., and they have a considerable influence on wine quality. Moreover, the presence of anthocyanins in ripe berries is used as the accepted qualitative parameter for distinguishing red from white grapes, since these pigments are known to be present only in red berries. On the other hand, pyranoanthocyanins are important pigments for the colour stability of red wines and are known to be formed after berry crushing, during vinification and wine ageing. Scope of this work was to investigate the possible occurrence of anthocyanins in white grapes and pyranoanthocyanins in grapes generally. For this purpose a modern ULPC-MS/MS method was used, which was shown to be sensitive enough to detect and quantify anthocyanins in trace amounts. For the first time we provide clear evidence that the skin of international white grape cultivars (Chardonnay, Sauvignon Blanc and Riesling) contains measurable traces of anthocyanins. In addition, for the first time we report clear proofs about the presence of pyranomalvidin 3-O-glucoside (B-type vitisin) and carboxypyranomalvidin 3-O-glucoside (A-type vitisin) in fresh grapes and we quantify them.