Looking for homebrewing gift ideas? Check out our previous gift guides here or here!
Also, if you enjoy BrewUnited, please consider doing your Amazon shopping via our affiliate link!
Also, if you enjoy BrewUnited, please consider doing your Amazon shopping via our affiliate link!
Jump to:
1
I have four questions regarding yeast derived phenols that I hope someone can shed some light on.
1. Does anyone know of any studies (published or unpublished) showing that stressing yeast fermentation via lack of oxygen, low pitching rate, or high gravity can cause phenolic off-flavors in beers fermented with POF- yeast? As far as I can tell, phenolic production is only tied to one or two genes, and yeast that have that gene will produce significant amounts of phenolics, while others will not. I know that genetic drift could maybe cause this, but outside of that can POF- be made to produce phenols?
2. Same question above, but for POF+ yeast. Does stress create more phenols?
3. Does anyone know of an extensive list of POF+/- yeasts from White Labs or Wyeast, including non-Belgian strains?
4. How many English Ale strains are POF+? I've heard claims that some English Ale strains are POF+, but I can't find direct evidence for that.
Thanks,
Dan
Posted 34 days ago.
Edited 34 days ago by DanABA
I replied to the thread on Facebook. I really hope you get some answers. These are fascinating questions.
Posted 34 days ago.
Yep, thanks for your help, Dan.
Posted 34 days ago.
Someone with more chemistry background can speak up here, but the way I understand it, phenolics aren't really produced by yeast per se. Yeast decarboxylate phenolic acids in wort to make phenols. So, to get to the root of your question, there can't be phenols without the right precursors in the wort. It doesn't matter what kind of stress you put the yeast under or if they're POF+/-. You can also get thermal decarboxylation, meaning you can make phenols in your wort simply by boiling without any interaction from the yeast. You can also get reduction in phenol levels through filtering with activated charcoal and fining agents. So if you're trying to set up some kind of experiment to answer these questions, you have to take some of these factors into consideration.
To answer some of your other questions - no, POF- yeast can't be made to make POF unless you have some serious genetic drift. Testing for POF is the way breweries often look for contamination, so if it were possible, this test would be invalid. I suspect you're asking about British strains specifically because of some old descriptors of British beers, right? Recall that until very recently, British brewers all used mixed pitches (even if they didn't know that) and the POF+ part was probably the Brett.
Posted 34 days ago.
Jump to:
1
