Comprehensive study of the dynamic interaction between SO₂ and acetaldehyde during alcoholic fermentation

Area of Science:

• Enology
• Yeast Metabolism
• Wine Chemistry

Background:

• Sulfur dioxide (SO2) is commonly used in winemaking.
• Its impact on yeast metabolism and acetaldehyde production is complex.
• Understanding SO2's role is crucial for wine quality.

Purpose of the Study:

• To investigate the effect of initial SO2 content in synthetic grape juice on yeast metabolism.
• To analyze the production of acetaldehyde and its relationship with SO2 levels.
• To determine the influence of SO2 on wine aroma compound synthesis.

Main Methods:

• Fermentation of synthetic grape juice with varying initial SO2 concentrations.
• Measurement of yeast lag phase duration.
• Quantification of free and bound acetaldehyde.
• Analysis of volatile aroma compounds and redox equilibrium (NADPH/NADP+).

Main Results:

• Increased initial SO2 lengthened the yeast lag phase.
• A threshold SO2 concentration (30 mg L-1) established an equilibrium between SO2 diffusion and yeast production.
• Maximum free acetaldehyde accumulation occurred at this SO2 equilibrium.
• SO2 significantly altered the synthesis of sulfur-related and carbon volatile compounds, impacting aroma profiles.
• Only free acetaldehyde, not SO2-bound acetaldehyde, affected yeast metabolism.

Conclusions:

• Initial SO2 concentration critically influences yeast fermentation kinetics and acetaldehyde levels.
• SO2 affects both sulfur and carbon volatile compound synthesis through redox disruption.
• The equilibrium between SO2 diffusion and yeast production is a key factor in acetaldehyde accumulation and aroma development.