How exactly does acidity affect yeast? - Home Brew Forums
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Old 03-13-2012, 11:21 PM   #1
Nateo
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I suspect it has something to do with the H+ ions interfering with proton ATPase and secondary active transport, but I'm not sure.


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Old 03-14-2012, 12:09 AM   #2
ajdelange
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Yeast are quite acidophillic. This is how they compete with bacteria i.e. by establishing a low pH in the wort. The corresponding pH drop can be used as an indicator that the fermentation is well underway.

Yeast are not damaged by washing down to pH 2. Beyond that is not so good for them. Exactly which enzymes it is that are denatured I do not know but it is doubtless denaturing of enzymes that does the harm.

 
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Old 03-14-2012, 12:23 AM   #3
Nateo
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Quote:
Originally Posted by ajdelange View Post
Yeast are not damaged by washing down to pH 2. Beyond that is not so good for them. Exactly which enzymes it is that are denatured I do not know but it is doubtless denaturing of enzymes that does the harm.
When you're acid-washing yeast, the yeast isn't transporting anything through the cell walls, right? The low pH would make it go dormant? Under normal circumstances, the yeast is able to maintain an internal pH that keeps the enzymes from being denatured at 2 pH, but under 2 something happens to change that?
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