Exploring the impact of ethanol removal in Nero d’Avola wine

Since the last 20 years, the wine industry has been facing to the climate change causing the increase of the sugar content of must and, consequently, the ethanol content in wine. This aspect is in contrast with the increasing consumers’ demand for low and free-ethanol wines which market has becoming more and more important. Different technologies are available for the partial or total removal of ethanol as distillation, evaporation under vacuum and membrane-based systems. The impact on wine composition can differ depending on the dealcoholisation approach, extend of ethanol removal and the wine subjected to the dealcoholisation (Sam et al., 2021). In this regard, further investigations are needed to expand the knowledge related to the effects of dealcoholisation applied to different wines generating additional evidences on this winemaking step of increasing application. On these bases, the research aimed to (i) evaluate the effects of removing different concentrations of ethanol on the chemical and sensory profiles of the wine and (ii) analyse the evolution of wine with lower alcohol content. Nero d'Avola wines (Sicily, Italy) produced in vintage 2024 in 4 different wineries were collected after the malolactic transformation and subjected to ethanol removal using a combined membrane-system consisting in nanofiltration and reverse osmosis technologies. The ethanol removal was carried out at -2% and -4% (v/v). After the dealcoholisation treatment, the wines were bottled and stored at 15±1°C up to 6 months. The sampling was also performed one month after the bottling. Aliquots of wines not subjected to dealcoholisation was bottled as control. The wines were characterized for general chemical composition (residual sugars, titratable acidity, tartaric acid, acetic acid, malic acid, lactic acid content, acetaldehyde, glycerol), flavonoids and anthocyanins, colour index, procyanidins (vanillin index) and tannins (methylcellulose index). The results showed the ethanol removal at -2% (v/v) led in modest decreases of titratable acidity (up to -14%) and tartaric acid (up to -10%), while at -4% (v/v) ethanol reduction the decreases of titratable acidity and tartaric acid were more pronounced (-31% and -34% as average for titratable acidity and tartaric acid, respectively). Acetaldehyde dropped (up to -68%) at the -4% ethanol in most of the wines. The applied dealcoholisation conditions on Nero d’Avola wines led also to relevant changes of the phenolic composition and colour index. In particular, a decrease of flavonoids was observed for the ethanol removal at -4% reaching -46% in comparison to the control wine. Similarly, the content of anthocyanins decreased resulting about halved after the ethanol removal at -4%. Nonetheless, negligible decreases of both flavonoids (up to -11%) and anthocyanins (up to -13%) were found for two wines considered in the study suggesting the specific wine features could cause a significant modification of its composition due to the dealcoholisation treatment. The colour intensity also declined in accordance to the anthocyanin decrease. As expected, sensory analysis revealed that wines with a -2% ethanol were fruitier and more floral, with higher olfactory intensity compared to those with a 4% reduction. The study provides further knowledge on the impact of dealcoholisation performed by a combined system for Nero d’Avola wine subjected to the ethanol removal for the first time, to the best of our knowledge. Further investigations are on-going to evaluate the evolution of partially dealcoholised wines as well as to evidence the sensory change occurring on Nero d’Avola, a key wine for the Sicilian wine industry.