Article on the physiology and fermentation performance of various lager yeast strains and Saccharomyces eubayanusPosted in News on May 22nd, 2013 by suregork
An article on the physiology and fermentation performance of various lager yeast strains and Saccharoyces eubayanus that I co-authored has been accepted for publication in the Yeast journal and the article was just released online. We found that the fermentation performance of Frohberg strains in wort were superior to that of Saaz strains and S. eubayanus, but the Saaz strains and S. eubayanus were the least sensitive to cold (growth at 10 °C). Surprisingly, it was found that fermentation performance of S. eubayanus was limited by the inability to take up maltotriose. This explains the poor attenuation levels I also saw in my S. eubayanus homebrew. Here is the abstract:
Two distinct genetic groups (Saaz and Frohberg) exist within the hybrid Saccharomyces pastorianus (S. cerevisiae x S. eubayanus) taxon. However, physiological/technological differences that exist between the two groups are not known. Fermentative capability of the parental S. eubayanus has likewise never been studied. Here, 58 lager strains were screened to determine which hybrid group they belonged to, and selected strains were characterized to determine salient characteristics. In 15 °P all-malt wort fermentations at 22 °C, Frohberg strains showed greater growth and superior fermentation (80 % apparent attenuation, 6.5 % alcohol by volume in 3-4 days) compared to all other strains and maintained highest viability values (>93 %). Fermentation with S. eubayanus was poor at the same temperature (33 % apparent attenuation, 2.7 % ABV at 6 days and viability reduced to 75 %). Saaz strains and S. eubayanus were the least sensitive to cold (10 °C), though this did not translate to greater fermentation performance. Fermentation with S. eubayanus was poor at 10 °C but equal or greater to that of the Saaz strains. Performance of Saaz yeast/S. eubayanus was limited by an inability to use wort maltotriose. [14C]- Maltotriose transport assays also showed negligible activity in these strains (≤ 0.5 µmol/min/g dry yeast). Beers from Saaz fermentations were characterized by 2 – 6 fold lower production of the flavour compounds methyl butanol, ethyl acetate and 3-methylbutyl acetate compared to Frohberg strains. Higher alcohol and ester production by S. eubayanus was similar to that of Frohberg strains.
- Gibson, B.R., Storgårds, E., Krogerus, K., Vidgren, V., (2013) Comparative physiology and fermentation performance of Saaz and Frohberg lager yeast strains and the parental species Saccharomyces eubayanus. Yeast. In Press. DOI: 10.1002/yea.2960