Effect of dehydration process on mineral content, phenolic compounds and antioxidant activity of Cabernet Sauvignon and Merlot grapes

•The controlled dehydration process changes the chemical composition of red grapes.•Highest values for individual phenolic compounds are observed in dehydrated grapes.•Antioxidant activity is highest in dehydrated grapes than control samples.•Dehydration process increase the content of minerals of the grapes.

Cabernet Sauvignon and Merlot grapes were dehydrated under controlled conditions (7 °C and 35% relative humidity) and the effect of this process on the mineral composition, phenolic profile and antioxidant capacity was investigated. The grapes were analysed at the moment of harvest and then every 7 days until reaching 30% and 40% weight loss. A significant difference was observed between the chemical compositions of the control and dehydrated grapes. The dehydration process increased the soluble solids content, total acidity, total polyphenols, total monomeric anthocyanin content, colour intensity, individual phenolic compounds, antioxidant activity and elemental composition. Principal components analysis demonstrated the separation of the samples according to the different dehydration percentages, indicating that changes which occurred in the composition of the grapes are correlated with the percentage of water loss, which influences the final characteristics of the musts.