Effects of oak aging on quality and sensory attributes of wines produced from smoke-exposed grapes

Abstract

Wildfires are becoming increasingly prevalent due to climate change. During wildfire events, volatile phenols (VPs) are released in fresh smoke from the combustion of wood lignin. These compounds are absorbed through grape berry skins and are rapidly glycosylated. Wines produced from smoke-impacted grapes can display medicinal, smoky, and retro-nasal ashtray-like characters. Once grapes are exposed, few effective mitigation strategies exist to remediate these sensory defects. In addition, matrix differences among grape varieties and winemaking styles influence smoke expression, as well as potential synergistic effects among VPs. In this study, serial dilutions of non-impacted and impacted wines (intentionally smoked post-harvest) were used to create wines with varying smoke levels in Cabernet Sauvignon and Chardonnay. Oak barrel aging (12 months in new French or American oak) was evaluated as a mitigation strategy, with stainless steel-aged wines serving as controls. Free and total VPs, along with individual bound glycosides, were quantified using GC-MS and LC-QqQ-MS, respectively. Descriptive analysis assessed sensory attributes, and Wine CualityTM was used to evaluate overall quality. A linear relationship was observed between VP and glycoside concentrations and the proportion of smoke-impacted wine in each blend. Wines with higher VP levels also received higher smoke intensity ratings from the sensory panel. Overall, barrel-aged wines showed reduced ashy aftertaste and lower intensities of smoke-related attributes in both varieties. Stainless steel wines were fruitier but expressed stronger smoke characters. Oak-aged wines received higher quality ratings and fewer smoke-related off-flavors than stainless steel counterparts. At very low dilutions of smoke-impacted wine, quality ratings increased in both aging treatments despite measurable increases in VP markers. Oak-aged Cabernet Sauvignon containing low levels of smoke-impacted wine was rated higher in quality than the non-impacted control, a trend less evident in Chardonnay. These findings enhance our understanding of how varying levels of grape smoke exposure influence wine sensory properties and demonstrate that oak barrel aging may serve as a viable strategy to mitigate the overall perception of smoke-related attributes across different wine matrices and taint levels. It also shows the potential use of Wine CualityTM as an alternative method for quality assessment.

References

Mirabelli-Montan, Y. A., Marangon, M., Graça, A., Mayr Marangon, C. M., & Wilkinson, K. L. (2021). Techniques for mitigating the effects of smoke taint while maintaining quality in wine production: A review. Molecules, 26(6). https://doi.org/10.3390/molecules26061672

Parker, M., Jiang, W., Coulter, A. D., Siebert, T. E., Bilogrevic, E., Francis, I. L., & Herderich, M. J. (2024). Prevalence of wildfire smoke exposure markers in oaked commercial wine. American Journal of Enology and Viticulture, 75(1), 0750017. https://doi.org/10.5344/ajev.2024.23076

Parker, M., Osidacz, P., Baldock, G. A., Hayasaka, Y., Black, C. A., Pardon, K. H., Jeffery, D. W., Geue, J. P., Herderich, M. J., & Francis, I. L. (2012). Contribution of several volatile phenols and their glycoconjugates to smoke-related sensory properties of red wine. Journal of Agricultural and Food Chemistry, 60(10), 2629–2637. https://doi.org/10.1021/jf2040548