Smoke taint is the term given to the objectionable smoky, medicinal, and ashy characters that can be exhibited in wines following vineyard exposure to bushfire smoke. This study sought to investigate the stability of smoke taint by determining changes in the composition and sensory properties of wines following 5 to 6 years of bottle aging. Small increases in guaiacol and 4-methylguaiacol (of up to 6 μg/L) were observed after bottle aging of smoke-affected red and white wines, while syringol increased by as much as 29 μg/L. However, increased volatile phenol levels were also observed in control red wines, which indicated that changes in the composition of smoke-affected wines were due to acid hydrolysis of conjugate forms of both naturally occurring and smoke-derived volatile phenols. Acid hydrolysis of smoke-affected wines (post-bottle aging) released additional quantities of volatile phenols, which demonstrated the relative stability of glycoconjugate precursors to the mildly acidic conditions of wine. Bottle aging affected the sensory profiles of smoke-affected wines in different ways. Diminished fruit aroma and flavor led to the intensification of smoke taint in some wines, but smoke-related sensory attributes became less apparent in smoke-affected Shiraz wines, post-bottle aging.
Keywords: acid hydrolysis; bottle aging; cultivars; guaiacol glycoconjugates; smoke taint; volatile phenols; wine.