Evolution and sensory contribution of ethyl acetate in sweet wines

Abstract

Ethyl acetate (EtOAc) is the main ester present in all wines, generally produced by yeasts during alcoholic fermentation and sometimes by bacteria during barrel ageing. Its odor is characterized by solvent notes, which give wines their acescent note [1]. Empirical observations have shown that in sweet wines, this note is often perceptible when tasting in the bottle, whereas it is not present at the end of barrel ageing. The perception of acescence is explained by an increase in EtOAc of the order of 100 to 150 mg/L after bottling in sweet wines. This phenomenon has also been observed in red wines, but its extent remains limited and unexplained [2]. The aim of this study is to establish the concentrations of EtOAc found in sweet wines and to study its sensory influence on their olfactory perception.

To assay the levels of EtOAc in a sensitive and precise way, an HS-SPME-GC/MS method was developed in the laboratory. A quantitative comparison was carried out between samples of wines made from Botrytis cinerea and “passerillage”. The results revealed great variability in EtOAc, with concentrations ranging from 90 to 300 mg/L, highlighting both an estate effect and a vintage effect. The origin of such high levels compared to other types of wine is unexplained in the literature, and certainly have a non-negligible impact on the sensory space of sweet wines [3]. As EtOAc perception is matrix-dependent, its detection threshold has been determined here at 136 mg/L in a botrytized sweet wine by two different panels. To complement these sensory data and further investigate the contribution of EtOAc, a concept of complexity threshold was introduced and investigated, on the same model as the detection threshold. Samples containing the 95 and 115 mg/L EtOAc additions were judged significantly more complex than the wine with no addition. These results showed that EtOAc can play a role in wine complexity. Both concentrations were infra-threshold, demonstrating that EtOAc has an indirect influence on olfactory perception. When EtOAc was clearly detected, the wine loses complexity and may even be rejected. These results provide a better understanding of the influence of EtOAc on the sensory space of sweet white wines.

References

[1] Ribereau-Gayon, J. (1973). Oeno one, 7 (2), 79-92.

[2] Cassino, C., Tsolakis, C., Bonello, F., Gianotti, V., Osella, D. (2019). Food Reasearch International., 116, 566-577.

[3] Sarrazin, E., Dubourdieu, D., Darriet, P. (2007). Food Chemistry, 103 (2), 536-545.