A first approach towards the relationship between grape skin cell-wall composition and anthocyanin extractability Original Research Article

The composition of skin cell-walls from four different grape varieties (Vitis vinifera L., cv. Cabernet Sauvignon, Merlot, Syrah and Monastrell, the later harvested in three different locations) has been studied, trying to correlate those differences found in cell-wall composition among varieties with their degree of ripeness and with the easiness of anthocyanin extractability. The results of an anthocyanin extractability assay showed that the anthocyanins from Monastrell grape skins might be more difficult to extract than those from the other varieties. The study of the cell-wall composition showed some differences in uronic acids, cellulosic glucose, proteins and polyphenol content of cell-walls among varieties, and also differences between the Monastrell grapes cultivated in different locations were detected. Little differences could be found among the different samples regarding the non-cellulosic neutral sugars. In trying to look if differences in the extractability index were related to cell-wall composition and to help to clarify some of the mechanism involved in the anthocyanin extractability, a multiple regression analysis was conducted. The results showed that a model could be built up explaining a high percentage of the variability in the extractability index, using the content of the different components of the skin cell-wall as independent variables. Following this approach, the differences on the easiness of anthocyanin extractability in grape samples could be based in differences in pectin and cellulose content, but also, differences occurring on arabinoxylan, arabinogalactan and xyloglucan could be of importance.