Determination of the impact of bottle colour and phenolic concentration on pigment development in white wine stored under external conditions.

The exposure to sunlight of a Sauvignon blanc wine stored in bottles of different colours has been examined. Wine in darker bottles (Antique Green and French Green) showed considerably more colour development than wine in clear (Flint) or lighter (French Green) bottles, provided a high concentration of catechin-type phenolic compounds was present. Xanthylium pigments were identified by LC-MS as one of the main contributing phenolic pigments to the increased colour in the dark bottles. This is the first observation of yellow xanthylium pigments in a white wine. A Principal Component Analysis of the variation in absorbance measurements at Day 59 of the exposure further confirmed the importance of bottle colour on the result. One component, dominated by the darker Antique Green and Classic Green, reflected the development of colour at 440 and 520 nm. The second component, to which the Flint and French Green bottles contributed the most, was based on a decrease in the 280 nm absorbance. The implication of these results for the safe storage of wine is discussed.