Gas Chromatography-Olfactometry (GCO) screening of odorant compounds associated with the tails-off flavour in wine distillates

Abstract

The development of off-flavours in wine distillates, particularly those associated with the tails fraction, is a key issue in the production of high-quality spirits. The traditional distillation of wine to obtain wine spirit is carried out discontinuously in a still, requiring the precise separation of the distillation fractions: heads, hearts, and tails, each with a distinct chemical composition [1]. The final fraction, known as the “tails,” is typically separated due to its heavy and unpleasant aroma, which is identified in the sensory evaluation of wine spirits [2] and is negatively correlated with overall wine spirit quality [3]. However, the specific compound or compounds responsible for this tails-off flavour have yet to be identified.

Therefore, this study aims to identify and characterize the volatile compounds responsible for the “tails-off” flavour in certain wine distillate tails fractions using Gas Chromatography-Olfactometry (GCO), an analytical technique that combines gas chromatography/flame ionization detector (GC-FID) with human olfactory detection, allowing for the direct identification of odorant compounds in complex matrices like wine distillates. A frequency detection method was applied using nine sniffers to evaluate the detected odour notes while the compounds were simultaneously eluted in the FID detector. This approach aids in identifying compounds with “tails” odour notes. In parallel, gas chromatography/mass spectrometry (GC-MS) was used to determine the exact identity of the compounds.

The initial results of this study reveal the presence of compounds with both pleasant and unpleasant odour notes in the tails fraction, originating from different chemical families. For example, the sniffers detected the presence of diacetyl, which imparts butter, caramel, and vanilla notes, as well as isovaleric acid, which has cheese and foot odour notes. However, no compound was detected in the analysed tails fraction with a distinct “tails” odour. Most of the compounds with heavy and unpleasant aromas belonged to the fatty acid family.

By identifying the specific odorant compounds responsible for the tails-off flavour, this research lays the groundwork for potential strategies in distillation process optimization, aimed at reducing off-flavour development and improving the overall sensory quality of wine-based distillates.

References

[1] Zanghelini, G., Giampaoli, P., Athès, V., Vitu, S., Wilhelm, V., Esteban-Decloux, M. (2024). Food Res.Int., 178, 113977.

[2] Penã y Lillo, M., Latrille, E., Casaubon, G., Agosin, E., Bordeu, E., Martin, N., (2005). Food Qual. Pref., 16, 59-70.

[3] Caldeira, I., Mateus, A.M., Belchior, A.P. (2006). Anal.Chim.Acta 563: 264-273.