Optimization of Beer Fermentation with a Novel Brewing Strain Torulaspora delbrueckii Using Response Surface Methodology

MBAA TQ http://dx.doi.org/10.1094/TQ-54-1-0215-01 | VIEW ARTICLE
Maximilian Michel, Tim Meier-Dörnberg, Fritz Jacob, Hubertus Schneiderbanger, Korbinian Haselbeck, Martin Zarnkow, and Mathias Hutzler. Research Center Weihenstephan for Beer and Food Quality, Technische Universität München, Alte Akademie 3, 85354 Freising, Germany.
The use of novel brewing strains coming from the non-Saccharomyces sector adds new challenges but also new desirable aromas to beer. Some research teams have focused on screening new yeast species from biodiversity for their fermentation potential. The next step in creating novel brewing strains is the optimization of the fermentation process for the actual production of beer. Here a response surface methodology was used to adjust the fermentation process with a strain (T9, Torulaspora delbrueckii) found for potential use in a previous study. An oxygenation rate test was performed to investigate the oxygen requirement of the strain. Also, an evaluation of volatile flavor compounds and final flavor judgment by trained panelists were undertaken. The fermentation conditions were chosen according to prior testing at varying fermentation temperatures between 15 and 25°C and pitching rates due to relatively small cell sizes of between 50 × 106 and 120 × 106 cells/mL. Further, the optimal time of pitching from propagation in connection with viability, vitality, and cell count was investigated. The wort used was diluted to 12.5°P from wort extract for standardized conditions. Wort oxygenation until 10 mg/L of dissolved oxygen was found to be sufficient. Propagation cell counts reached up to 400 × 106 cells/mL in 28 h before viability decreased. Fermentation at 20°C and a pitching rate of 60 × 106 cells/mL led to the most desirable beer with a blackcurrant and honey-like flavor. A shift of flavor was found from honey-like at low temperatures to wine-like at higher temperatures.

Keywords: Torulaspora delbrueckii, Alternative yeast, Nonconventional yeast, Beer