Osmotolerant yeasts isolated from Tokaj wines

Area of Science:

• Oenology
• Microbiology
• Fermentation Science

Background:

• Tokaj Aszu wine production involves complex yeast fermentation.
• Aszu essence can be contaminated by undesirable yeasts, impacting quality.
• Understanding yeast physiology is crucial for optimizing wine production.

Purpose of the Study:

• To isolate and characterize yeasts from Tokaj Aszu wine and Aszu essence.
• To investigate the osmotolerance and other physiological traits of these yeasts.
• To assess the potential impact of these yeasts on wine fermentation and quality.

Main Methods:

• Isolation and culturing of yeasts from wine and essence samples.
• Physiological characterization including osmotolerance, ethanol tolerance, cell size, and morphology assessment.
• Comparative analysis of yeast isolates against known Tokaj Aszu strains.

Main Results:

• Isolated yeasts were identified as physiological races of Saccharomyces cerevisiae.
• High osmotolerance was confirmed as an inherited trait, not adaptive.
• No correlation was found between osmotolerance and ethanol tolerance, cell size, or morphology.
• An Aszu essence yeast isolate showed similar traits to the Tokaj Aszu strain, indicating competitive potential.
• High thermosensitivity was observed in the Aszu essence isolate.

Conclusions:

• Saccharomyces cerevisiae strains with inherent osmotolerance are key players in Tokaj Aszu fermentation.
• Contaminant yeasts in Aszu essence can possess characteristics similar to desirable wine strains.
• The identified thermosensitivity offers a method for selective elimination of undesirable yeasts, improving essence quality.