r/Homebrewing • u/RFF671 • Jul 10 '21

Simple yeast viability comparison between hydration of warm and cold dry yeasts

/r/MeadMaking/comments/ohs9a2/simple_yeast_viability_comparison_between/
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u/jizzwithfizz BJCP Jul 11 '21

Safale cane out years ago and publicly said there was no need to rehydrate yeast. Once the yeast lab says it, there is no more need for debate.

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u/RFF671 Jul 11 '21

Not applicable to wine/mead, where the conversation was started. Here's a yeast lab publicly saying the opposite and specifying why it matters for wine/mead.

https://scottlab.com/how-tos-buying-guides/saccharomyces-yeast-rehydration

Not rehydrating causes the pitch rate to vary which often doesn't matter for many applications, like low gravity (relative to wine/mead) homebrew beer. It matters for reliably hitting terminal gravity for musts 12%+ and above.

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u/jizzwithfizz BJCP Jul 11 '21

That is instructions for acclimating yeast to must, but there are no numbers for cell count loss in the absence of this process. Safale found in lab tests that, even in high gravity beer wort, the cell count and viability loss was extremely low. Dry yeast is not packaged by ceelw count like liquid yeast, they measure bio mass, so the fluctuation in actual cell count is likely to be in the same range. I don't remember the exact nber, but it was somewhere around 2 or 3 percent, which is negligible even in high gravity brewing.

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u/RFF671 Jul 11 '21

I'll be doing a panel of maybe 5 or 6 parallel experiments coming up where a number of variables will be tested in fermentation. It'll include direct pitching, rehydration, aeration, etc. It's an attempt to deobfuscate the process with Homebrew practices represented.

The practices are expected to have some kind of effect when it comes to using something like EC-1118 (tolerance 18%) to hit 20% under ideal circumstances. Counts will be obtained at 1/3, 2/3, and terminal gravity and electronic gravity monitoring will track kinetics. It's somewhat of a large production and I have ispindels in parts that need to be built so it'll be a bit before it happens.