Stability of Passion Fruit Type Aromas in New Zealand Sauvignon blanc Wines

Abstract

3-Mercaptohexan-1-ol (3MH) and 3-mercaptohexan-1-ol acetate (3MHA) are volatile thiol compounds that contribute to the distinctive passion fruit-type aromas of Sauvignon blanc (SB) wines, but issues remain about the persistence of these aromas in the bottle. The evolution of 3MHA and 3MH, in relation to polyphenol and antioxidant content, has been monitored in 16 Marlborough SB wines bottled in a research winery under both cork and screwcap over two years. These wines were compared to seven commercially bottled Marlborough SB wines, which had initial concentrations of 3MH from 2000 to 11,000 ng/L, and of 3MHA from 200 to 2300 ng/L, the high 3MHA values being a feature of the Marlborough region. 3MHA was the least stable of the volatile thiols, and after 3 months the concentrations in the research wines had decreased by 40–70%, and had largely disappeared after 12 months. These trends were matched by the loss of glutathione and flavan-3-ols, while the hydroxycinnamates were more stable. In the commercial wines, with better control of oxygen entry at bottling, the 3MHA concentrations declined by 20–45% in the 3 months after bottling. By contrast the levels of 3MH were much more stable, with an average loss of 10% after 3 months, and 40% after 12 months in the research wines. In some cases in both research and commercial wines, a sizeable decline in 3MHA levels over the first 3 months was accompanied by a rise in 3MH levels, likely because of conversion by hydrolysis of 3MHA to 3MH. Closure type did not have a major impact on rate of aroma loss.