Introduction
The post-fermentation phase plays a key role in wine quality, as yeast viability and acetaldehyde production affect sensory attributes and stability. This study evaluated the impact of nitrogen supplementation, cooling strategies and sulfur dioxide (SO₂) addition timing under winery conditions using Glera grape juice.
Methods
Two commercial Saccharomyces cerevisiae strains were tested in pilot-scale fermentations involving a decanting rest, two rackings (with either fast or slow cooling), and bottling, all in presence of wine lees. Nitrogen was supplied as ammonium (NH₄⁺) or as a combination of ammonium and amino acids (MIX). Yeast viability and acetaldehyde concentrations were monitored throughout post-fermentation and 67 days after bottling, with yeast cells remaining in contact with the wine. Mixed statistical models were applied to separate treatment effects from strain variability.
Results
MIX supplementation significantly improved yeast viability without increasing acetaldehyde concentration. Fast cooling and no SO₂ addition were associated with a higher number of viable cells and lower acetaldehyde concentration, whereas SO₂ addition increased the acetaldehyde concentration regardless of addition timing. Acetaldehyde concentration ranged from 12.1 to 36.2 mg/L across treatments.
Conclusions
Improving nitrogen management and post-fermentation cooling can positively influence wine quality by preserving yeast viability and limiting acetaldehyde concentration. The persistence of viable cells into the post-fermentation phase suggests their potential role in oxidation protection and wine maturation.