Combined effect of berry density and harvest date on the accumulation of phenolic compounds during ripening of ‘Italia’ table grape cultivar.

In the last years, consumers are increasingly demanding for healthy foods. Table grapes are considered an important source of bioactive compounds and therefore their presence in the market should be as long as possible while preserving the phenolic quality. The aim of this study was to determine the influence of berry heterogeneity in the vineyard and harvest date on the phenolic profile of Vitis vinifera L. cv. “Italia” table grapes during ripening. Grapes were harvested for five consecutive weeks and the single berries were densimetrically sorted. The results showed that this cultivar is rich in phenolic compounds with health-promoting properties, particularly at early harvest stage (341 and 178 mg/kg berries of total phenols in skin and pulp, respectively). Caftaric acid and p-coumaroyl-glucose were the most abundant compounds in the skin (28.95 – 51.93 mg/kg) and pulp (6.39 – 17.18 mg/kg), respectively. The evolution of phenolic compounds during berry ripening was modelled using response surface methodology according to the combined effect of sampling date and berry density. The regression models were highly significant for protocatechuic acid, catechin, epicatechin and t-resveratrol in the skin, and total hydroxycinnamoyl tartaric acids in the pulp (R ≥ 0.80). These models could be a valuable tool for better exploitation of maximum accumulation of phenolic compounds in the vineyard. An adapted sampling strategy could be implemented to increase the content of specific bioactive phenolic compounds, thus promoting the nutraceutical quality of fresh table grapes and ready-to-eat fruit salads.