Effects of prefermentative skin contact conditions on colour and phenolic content of white wines

Nine different white wines were elaborated by applying different skin contact times (2, 4, 6, 8, 12, 18 and 24 h) and temperatures (5, 10 and 20 °C). The colour (tristimulus colour parameters) and the phenolic composition of the musts and wines were determined at different winemaking stages. Although extended skin contact (maceration time ⩾12 h) increased significantly the levels of phenolics in the final wines, some of them were important compounds as antioxidant agents, such as caffeic acid. Related to wine colour, for longer skin contact periods (12, 18 and 24 h) at low temperatures (5 and 10 °C), it was found that the wines visually had an acceptable colour (L∗ values higher than 90 CIELAB units; a∗ values ranging from −0.86 to 1.32 units; b∗ values ranging from 5.40 to 21.30 units). So an exhaustive control of the skin contact conditions (time and temperature) is really important to reduce browning in white wines due to this vinification technique.