Effect of transient thermal shocks on alcoholic fermentation performance

Area of Science:

• Enology
• Yeast Physiology
• Fermentation Science

Background:

• Stuck and sluggish fermentations are significant issues in winemaking, causing economic losses.
• Extreme temperature exposure is an understudied factor contributing to fermentation problems.
• Understanding thermal impacts is crucial for optimizing winemaking processes.

Purpose of the Study:

• To identify thermal conditions causing stuck and sluggish fermentations.
• To investigate the impact of abrupt temperature changes on fermentation performance and yeast health.
• To evaluate the influence of yeast strain and nutrient availability on thermal stress response.

Main Methods:

• Fermentation trials using Saccharomyces cerevisiae strains (SBB11, T73, PDM) in synthetic grape must.
• Application of cold shocks (9°C and 1.5°C) and heat shocks (>32°C) at different fermentation stages.
• Assessment of fermentation performance, yeast viability, and vitality.
• Evaluation of nitrogen supplementation effects (diammonium phosphate addition).

Main Results:

• Cold shocks did not significantly affect fermentation performance.
• Heat shocks (>32°C) applied early in fermentation induced delays proportional to temperature increase.
• Fermentation delays were linked to reduced yeast cell vitality.
• Responses varied by yeast strain and nitrogen availability; nutrition improved post-heat shock performance.
• No stuck fermentations were observed under tested conditions.

Conclusions:

• Heat shocks, particularly in early fermentation stages, are a key factor in sluggish fermentations.
• Yeast strain and nutrient status modulate the impact of heat stress.
• Adequate must nutrition can mitigate negative effects of heat shock on fermentation performance.
• Further research into optimal temperature ranges and yeast management is warranted.