Impact of flavonoid and cell wall material changes on phenolic maturity in cv. Merlot (vitis vinifera l.)

In black berry varieties, the changes in flavonoid concentration and composition that occur in the last weeks before harvest only partially explain the improved sensory attributes linked with the progression of ripening. To better understand the factors involved in phenolic maturity of cv. Merlot, total and extractable anthocyanins and tannins were analyzed during late ripening, and the properties of skin cell wall material were determined. Over two consecutive years, both total and extractable anthocyanins increased until harvest, while minor variations in tannin concentration were found. A greater affinity of cell wall material for a commercial seed tannin was observed in the last ripening phases, preferentially involving high molecular mass tannins and galloylated forms. The increased anthocyanins could allow a more highly colored wine to be obtained with the progression of ripening, and the increasing affinity of skin cell wall material for seed tannins may play a role in the reduction of astringency. This research shows how different factors could influence phenolic maturity, confirming the original insights in Merlot.