Nitrogen supplementation during wine fermentation, cooling rate and SO₂ addition timing influence yeast viability and acetaldehyde production in the post-fermentation process.

The post-fermentation phase of still wine plays a crucial role in determining wine quality. This study evaluates the impact of key winery practices (including nitrogen supplementation during fermentation, cooling methods, and SO₂ addition) on yeast lees viability and acetaldehyde production during the post-fermentation stage. Two commercial Saccharomyces cerevisiae strains with distinct technological characteristics were assessed under a real vinification protocol involving a decanting rest, two rackings, and bottling. Nitrogen was supplemented either as ammonium alone (NH₄+) or as a mix of ammonium and amino acids (MIX). In order evaluate the effect of the treatments independently to the yeast strain, statistical mixed models were applied. Results showed that generally MIX supplementation significantly enhanced yeast viability without increasing acetaldehyde levels. Fast cooling and absence of SO₂ addition after fermentation were associated with higher viable cell counts and lower acetaldehyde concentrations. Although SO₂ addition consistently increased acetaldehyde, the timing of its application did not significantly affect its final concentration. These findings suggest that optimizing nitrogen nutrition and post-fermentation cooling strategies can improve wine quality by modulating viable cells concentration and acetaldehyde production. Moreover, the observed persistence of viable yeast cells highlights the need for further studies on their role in oxidation protection and wine maturation, providing a foundation for refined fermentation management practices.