Changes in Metal Ion Concentrations in a Chardonnay Wine Related to Oxygen Exposure during Vinification

Abstract

The impact of oxygen exposure during winemaking on metal ion concentrations in wine were investigated throughout the winemaking process in a Chardonnay wine. The concentrations of Al, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Sn, and Zn were determined using inductively coupled plasma-mass spectrometry. Oxygen exposure significantly impacted 13 metal ions at different phases of winemaking. However, only the concentrations of Cr, Cu, and Fe were impacted by early oxygen exposure during pressing, with lower Cr and Cu concentrations in wines that were aerobically pressed and lower concentrations of Fe in wines that were inertly pressed. The sequestering of Al, Cu, Ni, and Zn by wine lees was significantly affected by oxygen treatment, with lees collected from wines that were treated oxidatively sequestering significantly greater amounts of Cu and Zn and removing these metals from the wine supernatant. The metal ion that was most affected by oxygen exposure during pressing and handling was Cu, with significantly lower Cu measured in wines that were produced under oxidative conditions. It is known that elevated Cu concentrations have negative implications for wine aroma and flavour. This study demonstrated that oxygen management during winemaking significantly impacts metal ion concentrations in lees and wine, which may decrease the risk of developing taints and faults.

Copper(II) and Sulfur Dioxide in Chardonnay Juice and Shiraz Must: Impact on Volatile Aroma Compounds and Cu Forms in Wine

“…The concentrations of Cu and SO 2 at each sampling time point are shown in Tables 1 and 2. As expected, the concentrations of total Cu for each sample (i.e., control, LCu, HCu, LSO2, and HSO2) decreased dramatically in both Chardonnay and Shiraz wines (i.e., compare J/M to PAF, Tables 1 and 2) as a consequence of fermentation. The observed decrease in concentration was greater than 90% and 70%, respectively, consistent with the results previously reported by Bekker et al [42], Rousseva et al [35], and Vystavna et al [43]. After cold stabilization (PCold for Chardonnay, PB for Shiraz), an additional reduction in total Cu concentration was evident in both wines (Tables 1 and 2).…”

“…For the Chardonnay wine, the Cu treatments to the juice resulted in higher Cu concentrations in the final wine (i.e., compare control to LCu to HCu at PAF, Table 1). The bentonite treatment of the Chardonnay wines also removed 18%-44% of total Cu from the wine, as observed by Bekker et al [42], but LCu and HCu samples still contained more than triple the total Cu than the control at PB. After 15 months of bottle aging, there were trends of lower total Cu concentrations, but the differences were not generally significant (p ≤ 0.05, Table 1).…”

“…After cold stabilization (PCold for Chardonnay, PB for Shiraz), an additional reduction in total Cu concentration was evident in both wines (Tables 1 and 2). This was most likely due to the removal of Cu associated with the further settling of yeast lees and grape solids [42]. For the Chardonnay wine, the Cu treatments to the juice resulted in higher Cu concentrations in the final wine (i.e., compare control to LCu to HCu at PAF, Table 1).…”

“…After the cold stabilization (PCold for Chardonnay), the concentrations of H 2 S dropped to below its odor threshold of 1.1 µg/L [37] in all of the Chardonnay treatments. This may have been a consequence of the oxidative wine production process [42], the removal of some colloidal sulfide (e.g., complexed to Cu) during racking, and volatile H 2 S losses.…”

“…This may have been a consequence of the oxidative wine production process [42], the removal of some colloidal sulfide (e.g., complexed to Cu) during racking, and volatile H2S losses. It is interesting that the decrease in bound Cu (i.e., sulfide bound) with bentonite treatments (Table 1) did not show equivalent decreases in H2S ( Figure 1A).…”