🍷 Wine colour

Wine colour is the colour of a wine, which comes mainly from phenolic compounds and changes as the wine ages. Red wines contain more polyphenols (1–5 g/L) than white wines (0.2–0.5 g/L), and rosé wines fall in between.

In red wine the pigments are anthocyanins, which are responsible for the red colour of grapes and red wines. Their colour depends on pH, sulfur dioxide and copigments: at low pH they take the red flavylium form, and the colour shifts toward violet or blue as pH rises. Copigmentation with other phenolics generally stabilises the colour. White wines contain no anthocyanins; flavonols affect their colour only slightly, while hydroxycinnamic acids are easily oxidised and associated with browning.

Colour changes with age. Monomeric anthocyanins give young red wine its colour, but their concentration declines steadily during maturation and ageing. Pyranoanthocyanins, mostly yellow to orange, and polymeric pigments shift the hue from purple-red in young wines to brick-red in aged ones.

The OIV defines how to measure it: Resolution OENO 1/2006 describes a spectrophotometric method that calculates chromatic characteristics from the CIE 1976 trichromatic components X, Y and Z and imitates the colour sensation of real observers. Colour is described by tonality (the colour itself: red, yellow, green or blue), luminosity and chromatism (intensity of colouring), with the CIELab coordinates L* (0 is black, 100 is colourless), a* (positive red, negative green) and b* (positive yellow, negative blue).