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Old 12-22-2013, 07:54 PM   #1
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Default Fermentis rehydration instructions

The Fermentis website seems to have contradictory instructions for rehydration. If you go to the “Tips & Tricks” section, it shows:

Rehydrate the dry yeast into yeast cream by sprinkling it in ten times its own weight of water or wort. Gently stir and leave for 30 minutes. Finally, pitch the resultant cream into the fermentation vessel.
The rehydration step is done in a vessel outside the fermenter. The objective is to allow the yeast to recover all its functionalities before pitching.
Ale yeasts optimum rehydration temperature: 25 – 29C (77 – 84F)
Lager yeasts optimum rehydration temperature: 21 - 25 (69 - 77F)
After rehydration bacterial contamination can develop in the slurry. Follow our recommendations of maximum time between rehydration in sterile water and pitching depending on the storage temperature of the rehydrated yeast.
Stored at 4C – Pitch within 18 hours
Stored at 20C – Pitch within 6 hours
Stored at 25C – Pitch within 4 hours
Water or Wort?
Fermentis yeast can be rehydrated with sterile water or sterile wort.
After the wort has been boiled for at least 15 minutes, collect the volume required for rehydration and leave to cool to the required temperature. Rehydrate the yeast for 30 minutes. Pitch immediately into the tank after checking the temperature of wort, in order to avoid foam.
Don’t forget your rehydration essentials.
Respect recommended rehydration temperatures to assure the yeast membrane fluidity
Water or wort, whatever you choose make it sterile
Do not use chlorinated water it will kill the yeast
Do not use demineralized water

But going to the US-05 page (S-04 is the same), you see:

Sprinkle the yeast in minimum 10 times its weight of sterile water or wort at 27°C± 3°C (80°F ± 6°F). Leave to rest 15 to 30 minutes.
Gently stir for 30 minutes, and pitch the resultant cream into the fermentation vessel.
Alternatively, pitch the yeast directly in the fermentation vessel providing the temperature of the wort is above 20°C (68°F). Progressively sprinkle the dry yeast into the wort ensuring the yeast covers all the surface of wort available in order to avoid clumps. Leave for 30 minutes, then mix the wort using aeration or by wort addition.

I’ve emailed Fermentis twice but haven’t gotten an answer. I’ve looked through old threads but can’t find anything about the contradictory instructions.

I think probably any combination of these techniques would be fine. Does anybody have a more definitive answer?

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Old 12-22-2013, 08:16 PM   #2
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Rehydrate with warm water, not wort, for best results. Sprinkle the dry yeast over the water without letting it clump and let it sit for 15 minutes. Stir. If it is still more than 10° F warmer than your wort, add a little bit of wort to slowly lower temp 5-10° at a time. Repeat once or twice if necessary. Pitch.

Check out the Dry Yeast FAQ sticky, it goes over rehydration among other things and has the process listed in Yeast by Chris White and JZ.

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Old 12-22-2013, 09:20 PM   #3
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What he said.

It’s a question of timing. They’re saying that if you do this ahead of time, you should probably stick it in the fridge. Ideally you would time this so it’s ready when you need it.

The temperature is not critical. “Yeast” says 95F-105F, I wouldn’t go over that. It should be warm sterilized water, that is critical.

I boil the water, then pour it into a flask. A measuring cup will work. Let it cool. When it’s no longer warm to the touch, about 90F, add the yeast. The water will continue to cool. Give it about 15 minutes to soak up the water then swirl it around a bit.

At this point cool it to pitching temp, it’s liquid yeast now. “Yeast” says ± 15°F, but I go for 5F.

Salinté

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Old 12-23-2013, 04:15 PM   #4
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Quote:
Originally Posted by boydster View Post
Rehydrate with warm water, not wort, for best results. Sprinkle the dry yeast over the water without letting it clump and let it sit for 15 minutes. Stir. If it is still more than 10° F warmer than your wort, add a little bit of wort to slowly lower temp 5-10° at a time. Repeat once or twice if necessary. Pitch.

Check out the Dry Yeast FAQ sticky, it goes over rehydration among other things and has the process listed in Yeast by Chris White and JZ.
Good FAQ - thanks. I've been using the method from the Yeast book (essentially the same as the Danstar instructions), but the contradictory instructions from Fermentis bother me. I brewed yesterday and tried the Fermentis Tips & Tricks method to see if I can tell a difference. I even used spring water instead of tap water since they instruct against using chlorinated water.
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