Wine bottle colour and oxidative spoilage: Whole bottle light exposure experiments under controlled and uncontrolled temperature conditions.

Exposure of a Chardonnay wine to light from a mercury vapour lamp under controlled temperature conditionsshowed that colour enhancement was dependent on bottle colour. The increase in colourationwas Antique Green < French Green < Arctic Blue < Flint, in agreement with the transmission characteristicsof each bottle type. Xanthylium pigments were identified as one component contributing to theobserved enhancement of colour. The presence of oxygen was shown to be a critical factor to initiatethe formation of these xanthylium pigments during light exposure. Without temperature control, winecolour development was highest in Antique Green and lowest in Flint. This alternate order reflects theability of the darker bottles to retain heat longer than lighter coloured ones as confirmed by surface temperaturedecay rates. Specific pigments contributing to the wine colour enhancement in uncontrolledtemperature/light exposure experiments could not be identified, although tentative evidence wasobtained for the presence of flavan-3-ol based compounds. The different bottle glass surfaces did notinfluence the rate of loss of dissolved oxygen or oxidation of ascorbic acid. The potential to developthe results obtained in this study to identify markers for light and/or temperature exposure of whitewines is discussed.