Development of an analytical method for the quantification of compounds responsible for the green character of wines: influence of ripeness on their levels

Abstract

Red wines can sometimes exhibit undesirable green, herbaceous, and vegetative aromas, negatively impacting their sensory profile and consumer acceptance. While certain grape varieties, such as Cabernet Sauvignon, are known for their green pepper notes due to the presence of pyrazines, these aromas are increasingly appearing in non-pyrazinic grape varieties with each vintage. This phenomenon may be linked to climate change and winemaking decisions aimed at avoiding excessively high alcohol levels. Beyond pyrazines, some studies have associated these green notes with the presence of specific carbonyl compounds [1, 2]. Traditionally, due to their poor chromatographic and spectrometric properties, these compounds have been analyzed using derivatizing agents [3], which require tedious analytical procedures. Furthermore, these methods shorten the operational lifetime of chromatographic columns. To address this, the objective of this work was to develop an analytical method to quantify carbonyl compounds while avoiding any derivatization steps. The proposed method includes a first extraction step using solid-phase extraction (SPE) prior to injection into a two-dimensional gas chromatographic system coupled with a mass spectrometer. Two different strategies for extracting the compounds were studied: deposition of 100 µL into Tenax tubes or the use of stir bar sorptive extraction (SBSE). Several parameters have been optimized, including breakthrough volume, elution conditions, solvent purge with Tenax tubes, and extraction conditions with SBSE. Good repeatability values, around 10% relative standard deviation, were found with both strategies. However, the repeatability worsened with the repeated use of the same Tenax tubes. This issue, along with the fact that better detection limits were achieved with SBSE, led to the decision to analyze real wine samples exclusively with this last strategy. Several wines made from the same grapes harvested at different ripeness levels were analyzed to study the evolution of carbonyl compounds with ripeness.

References

[1] Arias-Pérez, I., Sáenz-Navajas, M. P., de-la-Fuente-Blanco, A., Ferreira, V., & Escudero, A. (2021). Food Chemistry, 361, 130081.

[2] Mozzon, M., Savini, S., Boselli, E., & Thorngate, J. H. (2016). Italian Journal of Food Science, 28(2), 190–207.

[3] Zapata, J., Mateo-Vivaracho, L., Cacho, J., & Ferreira, V. (2010). Analytica Chimica Acta, 660(1–2), 197–205.