Photochemical glyoxylic acid production in white wine: Impact of light sources and ethanol concentrations

Exposing wine to light can cause photooxidation of tartaric acid to form glyoxylic acid, leading to detrimental wine development. The impacts of different light sources and the presence of ethanol on photochemical glyoxylic acid production in wine are unknown. A tartrate-buffer solution and commercially de-alcoholised Chardonnay, adjusted to different ethanol concentrations (0–12 % (v/v)), were exposed to three commonly used light sources for 1–2 weeks. The highest glyoxylic acid accumulation occurred under cool-white fluorescent lighting, followed by cool-white light-emitting diode (LED) and then yellow LED, which is consistent with increased emission intensities at wavelengths below 500 nm, especially those nearest to 340 nm. The presence of ethanol accelerated glyoxylic acid production but lowered the contribution of glyoxylic acid-derived spoilage pigments to wine colour. Of the light sources studied, yellow LED lighting produced the least photooxidative production of glyoxylic acid in white wine.