The authors thank The Rhone Rangers for support in conducting the research.

What makes a quality glass of wine? This question has no single or simple answer. Common conceptions of what comprises a “good wine” include nebulous terms such as “balanced” and often incorporate the appearance attributes of the wine (color and clarity) and its aroma, flavor and mouthfeel.

 

Economic studies have sought to answer this question and include “wine finish” (the lingering taste and flavor after swallowing or expectorating wine)⁴ as a factor influencing wine quality.^2,6

Wine finish remains an understudied area of research, but it is closely related to the well-studied attributes of wine aroma and flavor. It is important to note that wine is composed of much more than just the volatile compounds themselves. These other wine components include sugars, acids, ethanol and tannin and are termed “wine matrix components.”

Specifically, tannin and ethanol have been shown to contribute to the perception of aroma and flavor in red wine, impacting the volatility and intensity of certain aroma compounds.^5,7,8,11

Thus, to investigate the role of wine finish on wine quality and impact of the wine matrix components on wine finish, a study was conducted using experienced wine consumers. These consumers evaluated a commercial Syrah adjusted to varying tannin and ethanol levels. The low ethanol treatment was 9% alcohol, and the high was 14% alcohol. Each treatment was also adjusted to a high and a low tannin concentration using grape extracted tannins to create a total of four wine matrix treatments falling within the concentrations typical of red wines.

These wine matrix treatments were spiked with one of three flavors of interest (2-phenylethanol [floral]), 3-isobutyl-2-methoxypyrazine [bell pepper] and oak lactone [coconut]). Consumers evaluated the duration of finish in each of these samples using a digital timer and then responded to questions regarding the intensity of the finish and their acceptance of that finish.

The impact of the wine matrix on flavor finish duration indicated that there was no interaction between the tannin and ethanol levels themselves and that, overall, ethanol had a more dramatic impact on the duration of finish as compared to the influence of tannin level.

For all three flavors investigated, consumers found the high ethanol samples to have a longer duration of finish (measured in seconds). In particular, high-ethanol samples spiked with floral, coconut and bell pepper finished on average 12.4 seconds, 6.8 seconds and 7.7 seconds later, respectively, than the low-ethanol counterparts.

These results support previous studies that found increased ethanol concentration, which increases the solubility of most flavor molecules in wine, resulted in a reduced concentration of flavor volatiles in the headspace, decreased aroma intensity and increased flavor intensity.^7,9

Tannin concentration only significantly impacted bell pepper finish, resulting in a finish that was 5.6 seconds longer in the high-tannin treatments compared to their low-tannin counterparts. A similar interaction between pyrazines and molecules with phenolic rings was observed by J. Aronson and S.E. Ebeler.¹ With more tannin (more phenol rings), the pyrazine molecule responsible for the bell pepper finish is held in solution due to this interaction, resulting in a longer bell pepper finish.

To ensure that consumers were evaluating the flavor finish as intended, participants were asked to indicate which flavor they believed to be dominating the finish in each sample. Results indicated that about 50% of the consumers were able to correctly identify either coconut or bell pepper in the finish of the wines spiked with either coconut or bell pepper flavors, respectively. This rate of identification was significant as compared to chance and did not vary due to tannin or ethanol. However, floral finish was much more difficult to correctly identify.

The acceptance of each sample varied as a result of both ethanol and tannin, but it also varied depending on the flavor composition of the wine matrix. Consumers rated the high-ethanol treatments as more acceptable for both floral and bell pepper compared to low-ethanol counterparts.

However, for the coconut flavor, there was no significant difference in acceptance for the finish of samples of different ethanol levels. This difference was attributed to differences among consumers—different people like different flavors in their wines.

The results here indicated that the consumers in this study liked the bell pepper and floral notes and were pleased when those notes were extended in the finish. The lack of significance with reference to coconut in the high-ethanol samples compared to the low-ethanol samples is likely the result of a polarization in preference.

Broadly speaking, consumers preferred the low-tannin samples more than the high-tannin samples. This speaks to the general preference of consumers for lower tannin wines that do not elicit such an astringent mouthfeel. This has been observed by others who also reported decreased acceptance for wines spiked with exogenous tannin.3 

Conclusion
The matrix does make a difference when it comes to the length of flavor finish. In particular, increased ethanol content elongates the finish duration. This impact on the finish is noteworthy because it, in turn, impacts the acceptability of a wine.

Winemakers can now take this new knowledge into account when making processing decisions that may impact the ethanol or tannin content in their wines.

Bibliography
1. Aronson, J. and S.E. Ebeler. 2004 “Effect of polyphenol compounds on the headspace volatility of flavors.” Am. J. Enol. Vitic. 55, 13–21.

2. Beneratello, L., M. Piacenza and S. Sacchetto. 2009 “Taste or reputation? What drives market prices in the wine industry? Estimation of a hedonic model for Italian premium wines.” Appl. Econ., 41, 2197–2209.

3. Harbertson, J., G. Parpinello, B. Heymann and M. Downey. 2012 “Impact of exogenous tannin additions on wine chemistry and wine sensory character.” Food Chem. 131, 999–1008.

4. Jackson, R.S. 2002 Wine Tasting: A Professional Handbook. p. 13,269, Elsevier, San Francisco, CA.

5. Knoll, C., S. Fritsch, S. Schnell, M. Grossmann, D. Rauhut and M. Dutoit. 2011 “Influence of pH and ethanol on malolactic fermentation and volatile aroma compound composition in white wines.” LWT –Food Sci Technol. 44 (10), 2077–2086.

6. LeCocq, S. and M. Visser. 2006 “What determines wine prices: Objective vs. sensory characteristics.” J. Wine Econ, 1, 42–56.

7. Robinson, A.L., S.E. Ebeler, H. Heymann, P.K. Boss, P.S. Solomon and R.D. Trenglove. 2009 Interactions between wine volatile compounds and grape and wine matrix components influence aroma compound headspace partitioning.” J. Agric. Food Chem. 57,10313–10322.

8. Rodriguez-Bencomo, J.J., C. Mun?oz-Gonzales, I. Andu?jar-Ortiz, P.I. Martin-A?lvarez, M.V. Moreno-Arribas and M.A. Pozo-Bayon. 2011 “Assessment of the Effect of the Non-Volatile Wine Matrix on the Volatility of Typical Wine Aroma Compounds by Headspace Solid Phase Microextraction/Gas Chromatography Analysis.” J. Sci. Food Agric. 91 (13), 2484–2494.

9. Secor, A.C. 2012 “Effects of ethanol, tannin and fructose on the sensory and chemical properties of Washington State merlot.” Pullman, Wash: Washington State University. dissertations.wsu.edu/Thesis/Spring2012/A_Secor_041012.pdf.

10. Villamor, R.R., M.A. Evans, D.S. Mattinson and C.F. Ross. 2013 “Effects of ethanol, tannin and fructose on the headspace concentration and potential sensory significance of odorants in a model wine.” Food Res. Inter. 50, 38–45.

11. Villamor, R.R., M.A. Evans and C.F. Ross. 2013 “Ethanol, Tannin, and Fructose Concentration Effects on Sensory Properties of Model Red Wines.” Am. J. Enol. Vitic. 64, 342–348.