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Stability of high cell density brewery fermentations during serial repitching
Pieter J Verbelen1, Tinne M L Dekoninck, Sebastiaan E Van Mulders
1The Centre for Malting and Brewing Science, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Kasteelpark Arenberg 22, Box 2463, 3001, Heverlee, Belgium. Pieter.Verbelen@biw.kuleuven.be
Biotechnology Letters
|July 1, 2009
Summary
Higher pitching rates in beer fermentation boost productivity but require yeast preoxygenation. Preoxygenation ensures yeast stability and flavor quality during serial repitching in high cell density fermentations.
Area of Science:
- Brewing Science
- Yeast Physiology
- Fermentation Technology
Background:
- Increasing volumetric productivity in beer fermentation is often achieved using higher pitching rates (inoculum size).
- High cell density fermentations can lead to decreased yeast net growth, impacting physiological stability across generations.
- Maintaining yeast health and performance is crucial for consistent beer production and quality.
Purpose of the Study:
- To investigate the impact of oxygen conditions (wort aeration and yeast preoxygenation) on high cell density brewery fermentations.
- To evaluate yeast physiological and beer flavor stability over eight generations of serial repitching.
- To determine the necessity of adequate yeast growth for sustainable high cell density fermentations.
Main Methods:
- Comparison of high cell density fermentations with conventional fermentations.
- Application of different oxygen conditions: wort aeration and yeast preoxygenation.
- Evaluation of yeast physiological parameters (growth, viability, age) and flavor compounds (acetaldehyde, diacetyl) over eight generations.
Main Results:
- High cell density yeast populations adapted faster to fermentation conditions when preoxygenated.
- Yeast preoxygenation was essential for maintaining physiological and flavor stability in serial repitching.
- Non-preoxygenated yeast resulted in inadequate growth, reduced viability, increased yeast age, and elevated levels of acetaldehyde and diacetyl.
Conclusions:
- Adequate yeast growth is essential for sustainable high cell density fermentations and serial repitching.
- Yeast preoxygenation is a critical factor for ensuring yeast stability and desirable flavor profiles.
- Optimizing oxygen conditions supports the economical and technical viability of high-density brewing processes.
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