Postharvest stilbenes and flavonoids enrichment of table grape cv Redglobe (Vitis vinifera L.) as affected by interactive UV-C exposure and storage conditions

• Cold storage and UV-C improved health-promoting compounds content in Redglobe.
• Consistent level of piceids and quercetins was observed in treated grapes.
• Cyanidin and peonidin raised up to threefold after UV-C and 24 h of storage.
• A preferential synthesis of cyanidin over peonidin would seem provoked by UV-C.

Flavonoids and stilbenes are secondary metabolites produced in plants that can play an important health-promoting role. The biosynthesis of these compounds generally increases as a response to biotic or abiotic stress; therefore, in order to achieve as high phenolic accumulation as possible, the interactive effects of storage conditions (temperature and time) and UV-C radiation on polyphenols content in postharvest Redglobe table grape variety were investigated. During a storage time longer than 48 h, both cold storage (4 °C) and UV-C exposure of almost 3 min (2.4 kJ m−2) positively enhanced the content of cis- and trans-piceid (34 and 90 μg g−1 of skin, respectively) together with quercetin-3-O-galactoside and quercetin-3-O-glucoside (15 and 140 μg g−1 of skin, respectively) up to three fold respect to control grape samples. Conversely, catechin was not significantly affected by irradiation and storage treatments. With regard anthocyanins, the highest concentrations of cyanidin-3-O-glucoside and peonidin-3-Oglucoside were observed in Redglobe, stored at both room temperature and 4 °C, after 5 min (4.1 kJ m−2) of UV-C treatment and 24 h of storage. Gathered findings showed that combined postharvest treatments can lead to possible “functional” grapes, within normal conditions of market commercialization, responding to the rising consumers demand to have foods that support and promote health.