Changes in the expression of proteins involved in stress response. Changes in the relative spot volumes of the proteins (Table 1) involved in stress responses during five different ripening stages from véraison until full ripening of cultivar Barbera grape berry skins. The véraison stage (0 DAV) was considered as the moment when 50% of the berries started to change colour. Proteins were grouped according to their functions. Values are the mean ± SE of six 2-DE gels derived from two independent biological samples analyzed in triplicate.