Taint in grapes and wine as a consequence of vineyard exposure to bushfire smoke has resulted in significant financial losses for grapegrowers and winemakers in Australia, Canada, South Africa and the USA. Several volatile phenols have been identified in wines made from fruit harvested from smoke-affected grapevines; but the accumulation of smoke-derived volatile phenols in glycoconjugate precursor forms has also been demonstrated. The taint, characterized by objectionable ‘smoky’, ‘smoked meat’, ‘dirty’ and ‘ashy’ aroma and flavor attributes, is thought to be influenced by the duration and phenological timing of smoke exposure. However, the concentration of smoke taint marker compounds and intensity of smoke-related sensory attributes in wine might also depend on cultivar, and fruit maturity at harvest. This paper describes trials undertaken to determine to the extent to which smoke taint develops in wines made from smoke-affected grapes (i) from different grape varieties and (ii) harvested at different maturity levels (i.e. at total soluble solids of 16-20 °Brix vs. 22-25 °Brix). Three white grape varieties (Chardonnay, Sauvignon Blanc and Pinot Gris) and four red grape varieties (Shiraz, Cabernet Sauvignon, Merlot and Pinot Noir) were exposed to smoke under experimental conditions (for 1 hour) at approximately 7 days post-veraison. The impact of smoke exposure on wine sensory properties was evident, irrespective of grape variety, and descriptive sensory analysis readily differentiated control (unsmoked) and smoked wines. In a related trial, grapevines from two white grape varieties (Chardonnay and Sauvignon Blanc) and two red grape varieties (Shiraz and Merlot) were exposed to smoke at two levels of maturity. Smoke-related sensory attributes were more apparent in Sauvignon Blanc wine made from early-harvested fruit and in Chardonnay wine made from late-harvested fruit, only; whereas Merlot and Shiraz wines exhibited smoke taint irrespective of fruit maturity. The implications of these research findings for industry, with respect to detecting and assessing smoke tainted grapes and wine, will also be presented.

Impact of vineyard exposure to smoke on wine composition and sensory properties

251st National Meeting (2016)

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