Cryogenic fractionation as a post-fermentation strategy for partial dealcoholisation of red wine: impacts on acid balance, colour, and phenolics

A rise in popularity of no/low-alcohol beverages and increasing vineyard temperatures associated with climate change has driven research into and the subsequent improvement of dealcoholisation methods. Several studies focused on the effects of post-fermentation dealcoholisation methods have reported no significant effects to basic physio-chemical parameters, but volatile compounds are lost. Cryogenic fractionation is a potential method that preserves volatile compounds. There is limited published research regarding cryogenic fractionation and this study investigated whether it is an effective method for removing ethanol from wine. It also investigated any significant effects to chemical parameters. 750 mL of a commercially produced blend of Touriga Nacional, Touriga Franca, and Tinta Roriz at 12.5 % v/v was cryogenically treated at –15 °C. Fractionation of the thawing wine provided a 100 mL liquid fraction and 650 mL ice fraction, of 26.2 % v/v and 5.2 % v/v alcohol respectively. The chemical parameters of the ice fraction analysed were pH, TA, colour using the modified Somers colour and total phenols by Folin–Ciocalteu assays, and organic acid composition by HPLC. A one-way ANOVA and Kruskall–Wallis tests were performed, with post-hoc analysis using Tukey’s HSD and Dunn’s tests. Ethanol was significantly reduced to 5.2 % v/v. Tartaric acid concentration, TA, total phenolic concentration, and colour density were significantly reduced, however lactic acid concentration was significantly increased in the ice fraction. pH, malic acid concentration, and anthocyanin concentration were not significantly affected. The method implemented to carry out cryogenic fractionation was proven effective at partially but significantly removing alcohol from wine. KHT precipitation and a lack of lactic acid partitioning during the freezing of wine significantly altered TA but did not affect pH. KHT precipitation and the reduced solubility of anthocyanin-tannin co-pigments due to the temperatures of cryogenic fractionation is believed to cause a colour loss. This study demonstrates the potential of cryogenic fractionation to be used as an alternative method to effectively reduce alcohol in wine. Further work is suggested to establish a more comprehensive understanding of the impact on the wine beyond the chemical parameters and explore the viability of this method on a commercial scale.