Smoke tainted wine – what now?

Abstract

Wines made from grapes exposed to smoke from bushfires that burned during the 2019/20 Australian grape growing season were subjected to various amelioration techniques, including: the addition of activated carbons, molecularly imprinted polymers (MIPs), or a proprietary adsorbent resin (either directly, or following fractionation by membrane filtration); spinning cone column (SCC) distillation; and transformation into spirit or vinegar, via fractional distillation or fermentation by acetic acid bacteria, respectively. The efficacy of treatments was determined by comparing volatile phenols (VPs) and their glycoconjugates, as chemical markers of smoke taint and changes in the intensity of fruit and smoke-related sensory attributes in wines, distillate, and vinegar samples. In brief: activated carbons can remove free and glycosylated VPs from smoke-tainted wines to some extent, without stripping desirable wine aroma and flavour. MIPs were also effective in removing VPs but not VP glycoconjugates. In contrast, adsorbent resin removed both free (<90%) and bound VPs (<30%). However, membrane filtration followed by resin treatment of the resulting permeate removed >95% of VPs. SCC distillation alone cannot remediate smoke taint, but smoke-related attributes were significantly diminished when ‘stripped wine’ was treated with activated carbon and blended with its corresponding condensate. Fractional distillation yielded ‘heart’ distillate fractions that were considered suitable for spirit production. Lastly, the potential for smoke-tainted wine to be transformed into vinegar was also demonstrated. The choice (and success) of each treatment ultimately depends on the extent to which wine is tainted, but the cost of harvesting and processing smoke-affected grapes should be considered when evaluating the economic return of remediation.