Impact of Cu Fractions on the Light-Induced Spoilage Aromas of Chardonnay Wine at Variable Riboflavin Concentrations

Despite the known ability of copper(II) to suppress sulfidic aromas, particularly the Cu fractions associated with organic acids and Cu(I) thiol species, the action of these copper fractions on the accumulation of light-induced sulfidic aromas in bottle-aged white wine is unknown. Chardonnay wine, containing different concentrations of riboflavin and copper(II), was exposed to fluorescent light for 6.5 months. The Cu fractions were measured by colorimetry, volatile sulfur compounds by gas chromatography-sulfur chemiluminescence detector (GC-SCD), and volatile aldehydes by gas chromatography-mass spectrometry (GC-MS). The protective Cu fractions inhibited light-induced sulfidic odor accumulation; however, light exposure accelerated the loss of these Cu fractions, and this loss was further accelerated with elevated riboflavin concentration. Upon depletion of the protective Cu fractions, the presence of copper sulfides led to an elevated hydrogen sulfide concentration with further light exposure. The results demonstrated that Cu(II) offers transient protection against the deleterious effects of short-term light exposure but can promote reductive characters with long-term light exposure.