Colour and phenolic compounds in sweet red wines from Merlot and Tempranillo grapes chamber-dried under controlled conditions

► Changes in colour and in monomeric and polymeric phenols during the vinification process have been studied. ► Chamber drying increased the sugar content to about 31.4 °Brix in Merlot and Tempranillo grapes. ► The drying process causes skin rupture, facilitating the access to the pulp of phenolic compounds. ► The end-product contained acceptable tannins, colour and phenolic compounds in comparison with commercial sweet red wines.