Comparison of methods for the analysis of smoke related phenols and their conjugates in grapes and wine
Article first published online: 12 MAY 2011
© 2011 Australian Society of Viticulture and Oenology Inc.
Australian Journal of Grape and Wine Research
Volume 17, Issue 2, pages S22–S28, June 2011
How to Cite
WILKINSON, K.L., RISTIC, R., PINCHBECK, K.A., FUDGE, A.L., SINGH, D.P., PITT, K.M., DOWNEY, M.O., BALDOCK, G.A., HAYASAKA, Y., PARKER, M. and HERDERICH, M.J. (2011), Comparison of methods for the analysis of smoke related phenols and their conjugates in grapes and wine. Australian Journal of Grape and Wine Research, 17: S22–S28. doi: 10.1111/j.1755-0238.2011.00147.x
- Issue published online: 30 MAY 2011
- Article first published online: 12 MAY 2011
- Manuscript received: 18 January 2011, Revised manuscript received: 20 February 2011, Accepted: 3 March 2011
Background and Aims: Australian grape growers and winemakers have typically relied on guaiacol and 4-methylguaiacol measurements to determine smoke exposure of grapes following bushfires or prescribed burns. However, the guaiacol and 4-methylguaiacol content of grapes does not always correlate with the extent of taint in resultant wines. This study compared several methods for the analysis of smoke related phenols and their conjugates in grapes and wine, to determine their capacity as diagnostic assays for smoke exposure.
Methods and Results: Smoke-affected grapes were sourced from commercial vineyards exposed to bushfire smoke and from experimental field trials involving the application of smoke to grapevines, and small-scale wines were made from a number of these samples. Several analytical methods were applied to grapes and wine to determine the concentration of smoke related phenols and their conjugates. Strong correlations were observed between the glycoconjugate content of smoke-affected grapes and the concentration of guaiacol and 4-methylguaiacol released following acid hydrolysis of juice.
Conclusions: Where smoke-affected grapes contain low or non-detectable levels of guaiacol and 4-methylguaiacol, analytical methods that quantify their glycoconjugate forms (either directly or indirectly) provide a better indication of the extent of smoke exposure.
Significance of the Study: This is the first study to compare different methods for assessing smoke exposure in grapes and wine, through analysis of free and bound guaiacol and 4-methylguaiacol. These methods will allow grape growers and winemakers to more reliably assess smoke exposure of grapes, enabling better informed decisions to be made with regards to harvesting and processing smoke-affected grapes.