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Old 01-22-2013, 12:17 PM   #1
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Default Is this true about rehydrating dry yeast

saw this on a message board...wondering the validity. I have never rehydrated dry yeast since my first batch. I haven't seem to have any problems.


"Jamil says you lose 50% cell count by not rehydrating. Mr Malty calcs are based on rehydration when using dry yeast.


person's question...

What's the difference between rehydrating with water and rehydrating with wort (as you pitch dry into it)?"


message boards' answer....

Osmotic pressure. As the yeast begin to absorb water, initially the cell membrane cannot control what flows across the boundary. Everything flows in and out of the cell upsetting the needed balance of nutrients and salts inside the cells. This immediately kills roughly 50% of the cells.

Even with plain water it is still important to rehydrate at the right temperature (95 - 105F). Too cold or hot will also kill the cells.

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Old 01-22-2013, 12:19 PM   #2
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Yes, this topic has been discussed with much debate before. Search it....

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Old 01-22-2013, 12:20 PM   #3
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Yep, that's true. On the Danstar website, Clayton Cone goes into quite a bit of detail on the topic.

Yeast pitching rates are one of those things that won't jump up and slap you in the face if they're off, but the truly best beer requires careful attention to them.

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Old 01-22-2013, 12:23 PM   #4
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I did some poking around on HBT, but most of what I saw turned into the liquid vs dry debate. Thanks for the insights.

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Old 01-22-2013, 12:31 PM   #5
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Try using Google as your search engine. I usually get several HBT threads with google search, or use the site within search (i.e within HBT).

http://www.homebrewtalk.com/f13/rehy...cessary-62514/

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Old 01-22-2013, 01:04 PM   #6
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I've pitched dry yeast and had fermentation start within 24 hours and had good beer in the end.

I've pitched rehydrated yeast and had the same results.

But anymore I always rehydrate in water temps that the yeast maker states on the package.

I guess look at it this way, the yeast expert that packaged the yeast recommends it so why not follow the experts advice???

I also try to get that rehydrated yeast down within 10 degrees of the wort before pitching as well to keep it from getting shocked in anyway.

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