Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Considerations for Serial Repitching of Craft Beer-Relevant Ale Strains

72 views

Published on

Results from a yeast repitching project carried out by Escarpment Laboratories, as presented at the 2018 Brewing Summit in San Diego, CA.

Published in: Food
  • Be the first to comment

  • Be the first to like this

Considerations for Serial Repitching of Craft Beer-Relevant Ale Strains

  1. 1. Considerations for serial repitching of craft beer-relevant ale production yeast strains Isabelle Netto and Richard Preiss Escarpment Laboratories 8 Smith Ave, Guelph, Ontario, Canada
  2. 2. Who are we? • Escarpment Laboratories, Guelph, Ontario, Canada • Yeast supplier in Canada propagating many different yeasts for Canadian brewers • Research mandate @ Escarpment Labs • We want to give back to the brewing / science communities Richard Preiss Microbiologist & Cofounder Iz Netto R&D Biologist
  3. 3. • Breweries reuse liquid yeast cultures to reduce costs and increase production efficiency. • Yeast reuse often shortens lag phase and delivers more consistent fermentations. • Many breweries expect to repitch yeast for >8 generations with consistent results. Survey, Nov 2017 Yeast reuse/repitching in the craft brewery
  4. 4. Problems • Reports of inconsistent fermentation performance, viability and flavour in some yeast strains eg. the Vermont Ale and Old World Saison • Lack of empirical data concerning best practices for repitching of ale strains used by craft brewers. Most repitching studies center on industrial-scale lager production. !
  5. 5. Problems: ”Juicy IPA” specific • Vermont Ale and Foggy London Ale (and related commercial strains) typically used in this very popular craft beer style • Yeast strains are selected which accentuate hop aroma • Yeast management is challenging due to heavy pre- terminal dry hopping https://www.brewersassociation.org/communicating-craft/gabf-haze-craze/
  6. 6. Specific customer problems Customer 1 Customer 2 Customer 3
  7. 7. Study design 4 yeasts: Vermont Ale, Cali Ale, Foggy London Ale, Old World Saison generation: 1 2 3 4 5 6 7 8 9 10 11 12 Compressed air added Pure oxygen added 20L conical fermenters Gen 1 ~12.5ºP wort, 72.5ºF/22.5ºC, every 7 days yeast yield, viability, vitality Gen 2 generation: beer specific gravity sensory
  8. 8. Limitations • Hydrostatic pressure in small conicals very different from large scale industrial fermenters. • Yeast cells may be more stressed in large/tall fermenters • Cooling in pilot fermentors via internal coil, not glycol jackets • n = 1 for each fermentation generation (no statistical power)
  9. 9. 0 5 10 15 20 25 air oxygen ppmdissolvedoxygen Oxygenation Specs generation: 1 2 3 4 5 6 Compressed air added oxygen added 20L conical fermenters generation: Gen 1-3 Gen 4-12
  10. 10. Fermentation curves • One generation of Foggy London displayed an abnormal fermentation curve • Greatest inconsistency observed in the Saison yeast • Early generations inconsistent for Vermont Ale
  11. 11. Does fermentation rate change over yeast generations? • Specific gravity after 2 days consistent for most strains • The exception is the Saison yeast, which trended toward slower fermentation at later generations
  12. 12. Yeast cell yield • Cropped yeast cell count low by third generation • Quite variable – highlights importance for brewers to always perform cell counts • Improved and more consistent yields for Vermont and Cali Ale post- O2 1.0E+12 = 1 trillion cells
  13. 13. Impact of wort oxygen levels on harvested yeast viability • Cell viability (trypan blue stain) stabilized post-generation 3 • OWS, Vermont and Cali may have higher O2 requirements for optimal fermentation • Alternatively, this could be the yeast adapting to the fermentation environment dead live Image from Crowley, L. C., Marfell, B. J., Christensen, M. E., & Waterhouse, N. J. (2016). Measuring Cell Death by Trypan Blue Uptake and Light Microscopy. Cold Spring Harbor Protocols, 2016(7) +O2 +O2 +O2 +O2
  14. 14. Yeast viability / shelf life • Early generations (pre-O2) tended toward lower shelf life (faster viability drop) • Most clear in Vermont - viability drop in gens 1-3 (no added O2) vs. gen 4 and beyond (added O2)
  15. 15. Viability at 1 month cold storage • Properly oxygenated yeast maintains higher viability after 4 weeks of storage at 4ºC • Especially evident in Cali and Vermont • Occasional low viability values in Old World Saison, while Foggy London consistently high n.d.
  16. 16. Yeast vitality • Acidification Power (AP) Test • Proxy for yeast glycogen stores and proton efflux • For 3 of the 4 strains, AP over time is improved past Gen 3 • Vitality very low for Vermont Gen 1 yeast 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 1 2 3 4 5 6 7 8 9 ∆pH Weeks in Storage OWSaison Vitality Gen 1 Gen 4 Gen 8 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 5 6 7 8 9 ∆pH Weeks in Storage Vermont Vitality Gen 1 Gen 4 Gen 8 0 0.2 0.4 0.6 0.8 1 1.2 0 1 2 3 4 5 6 7 8 9 ∆pH Weeks in Storage Cali Vitality Gen 1 Gen 4 Gen 8 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0 1 2 3 4 5 6 7 8 9 ∆pH Weeks in Storage Foggy Vitality Gen 1 Gen 4 Gen 8
  17. 17. Sensory analysis
  18. 18. Sensory analysis
  19. 19. Perceived fruity and floral character decreases with repitching
  20. 20. What have we learned? • Some common craft beer ale strains are easier to repitch than others • Flavor intensity can decrease over serial yeast repitching • Wort DO seems to be very important to later yeast quality • Repitching issues in craft breweries could be improved by controlling and measuring wort dissolved oxygen • Know thy yeast strain! Strain added O2 vs. ferm rate added O2 vs. viability & vitality Ferm rate (over gen) Fruitiness (over gen) Vermont Ale n/a + n/a - Foggy London Ale n/a n/a n/a - Cali Ale n/a + n/a - Old World Saison -? + - -
  21. 21. Next directions • Smaller scale experiment with biological replicates • Detemine DO optimum for each yeast • Why do ale yeasts respond differently to added oxygen? • Are there other nutritional needs to optimize? • Are there clues among their genomes? Limitations to address • No statistical power • No comparison of gens 1-3 with and without added oxygen • Small sensory panel • Small fermentation vessels • No metabolite analysis (GC, HPLC – soon!) Whole genome sequencing will be a useful tool to identify, predict and control yeast behavior “Know Thy Yeast”
  22. 22. Cheers & thank you for listening! • Escarpment Laboratories, Guelph, Ontario, Canada • Yeast supplier in Canada propagating many different yeasts for Canadian brewers • Research mandate @ Escarpment Labs • We want to give back to the brewing / science communities Richard Preiss Microbiologist & Cofounder Iz Netto R&D Biologist
  23. 23. [supplemental] No major shifts in attenuation over 12 fermentations • No major changes were observed in the total attenuation by the yeast strains during repitching • No major trends in % attenuation after 24h 0% 20% 40% 60% 80% 100% 1 2 3 4 5 6 7 8 9 10 11 12 %Attenuation Generation Old World Saison Attenuation 24h Remaining 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 1 2 3 4 5 6 7 8 9 10 11 12 %Attenuation Generation Vermont Attenuation 24h Remaining 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100% 1 2 3 4 5 6 7 8 9 10 11 12 %Attenuation Generation Cali Attenuation 24h Remaining 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 1 2 3 4 5 6 7 8 9 10 11 12 %Attenuation Generation Foggy London Attenuation 24h Remaining
  24. 24. [supplemental] No major shifts in flocculation over 12 fermentations • [cells in solution at transfer] as proxy for flocculation • No major changes were observed in the flocculation by the yeast strains during repitching
  25. 25. [supplemental] Sensory analysis - heatmap • Does each strain have a distinct flavor profile? • Clustering analysis did not distinguish among the “clean” ale strains • At least our panel distinguished between the Saison and the ale strains!

×