Agriculture & Food, Volume 10, 2022

Abstract: Grape berries (Vitis vinifera L.) of “Muscat Hamburg” and “Sugraone Seedless”, soft and crisp variety, respectively, were harvested at seven developmental stages, from pre-veraison to ripening. During the first two stages and, in both varieties, a dramatic loss of firmness was observed, which was accompanied by a rapid increase in soluble sugar content and a decrease in acidity. Polygalacturonase, β- galactosidase, galactanase, pectin methylesterase, β-glucanase, α-galactosidase, β-glucosidase and xyloglucanase enzymatic activities in the berries of both varieties showed maximum activity during the pre-veraison and veraison stages, after which they decreased or remained more or less constant until the end of ripening. Throughout ripening, polygalacturonase and galactanase showed by far the highest activity of all the enzymes. During the first stages of ripening, polygalacturonase, galactanase, β- galactosidase and xyloglucanase activities were higher in the soft variety (“Muscat Hamburg"), while pectin methylesterase, β-glucanase and α-galactosidase were higher in the firm variety. The relationship between berry softening during ripening and the enzyme activities is discussed.