Direct NMR evidence for the dissociation of sulfur-dioxide-bound acetaldehyde under acidic conditions: Impact on wines oxidative stability

Abstract

SO₂ reaction with electrophilic species present in wine, including in particular carbonyl compounds, is responsible for the reduction of its protective effect during wine aging. In the present study, direct ¹H NMR profiling was used to monitor the reactivity of SO₂ with acetaldehyde under wine-like oxidation conditions. The dissociation of acetaldehyde bound SO₂ was evidenced suggesting that released free SO₂ can further act as an antioxidant. EPR and DPPH assays showed an increasing antioxidant capacity of wine with the increase in the concentration of acetaldehyde sulfonate. The presence of acetaldehyde sulfonate in wines was correlated with the overall antioxidant activity of wines. The first evidence of acetaldehyde bound SO₂ dissociation provides a completely new representation of the long-term protection efficiency of SO₂ during bottle aging.

Keywords: Aldehydes; Antioxidant activity; Chardonnay; Oxidation; White wine.