Smoke exposure effects on red wines: how much is too much?

Abstract

Increasing wildfire frequency in the United States has led to the indirect impact of smoke in vineyards, affecting grape quality and wine sensory attributes, commonly called “smoke taint”.¹ During a smoke event, grapes absorb volatile phenolic compounds, which are subsequently glycosylated, leading to potential negative sensory impacts in the resulting wines.² During the 2024 harvests, Vitis vinifera L. cv. Cabernet Sauvignon, Barbera, and Zinfandel grapes were intentionally exposed to various levels of smoke to establish threshold levels of free and bound volatile phenols in grapes that lead to noticeable changes in the sensory characteristics of their vinified wines. The wines were made using commercial practices at the UCD winery and stored until a complete sensory descriptive analysis (DA)³ and chemical analysis. All wines are analyzed for volatile phenols and their glycoconjugates concurrently using GC-MS/MS and LC-MS/MS, respectively.^4,5 Previously, in 2023, a DA panel evaluated Cabernet Sauvignon grapes. Judges rated highly smoked exposed grape (HE) samples higher for “astringency” and “vicious” mouthfeel as well as “smoky,” “cooked meat,” and “rubber” aroma, which correlated with significantly elevated levels of all volatile phenols analyzed compared to other treatments. However, HE grape samples were rated lower for “fresh and fruity” aromas than all other treatments, indicating that smoke suppresses fruit aromas in grape samples. The low (LE) and medium (ME) exposed grapes were not able to be sensorial differentiated from the control grape samples, even though ME grape and wine samples were significantly higher in all volatile phenols. For the wines, the trained DA sensory panel evaluated aroma orthonsal and the five “smoke taint” retronasal, in addition to tastes and mouthfeels. ME wines showed higher levels of “smoky,” “meaty,” “cigar box,” “wood,” and “old ashtray” aromas than LE and CE wines, with HE wines most affected. Preliminary results indicate high smoke exposure causes distinct sensory differences in grapes and wines. Similarly to 2023 wines, the presented project investigates three 2024 vintage red varietal wines. It shows the possible sensory profiles in response to different smoke levels in an experimental system that exposes grapes to various smoke levels. The aim is to develop threshold levels in common wine varietals of free and bound volatile phenols that can lead to unfavorable sensory attributes in the final wines.

References

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[2] 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. Contribution of Several Volatile Phenols and Their Glycoconjugates to Smoke-Related Sensory Properties of Red Wine. J Agric Food Chem 2012, 60 (10), 2629–2637. https://doi.org/10.1021/jf2040548.

[3] Lawless, H.; Heymann, H. Sensory evaluation of food: Principles and practices; Springer New York: New York, NY, 1998;

[4] Noestheden, M.; Thiessen, K.; Dennis, E. G.; Tiet, B.; Zandberg, W. F. Quantitating Organoleptic Volatile Phenols in Smoke-Exposed Vitis Vinifera Berries. J Agric Food Chem 2017, 65 (38), 8418–8425. https://doi.org/10.1021/acs.jafc.7b03225.

[5] Caffrey, A.; Lerno, L.; Rumbaugh, A.; Girardello, R.; Zweigenbaum, J.; Oberholster, A.; Ebeler, S. E. Changes in Smoke-Taint Volatile-Phenol Glycosides in Wildfire Smoke-Exposed Cabernet Sauvignon Grapes throughout Winemaking. Am J Enol Vitic 2019, 70 (4), 373–381. https://doi.org/10.5344/ajev.2019.19001.