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Old 03-19-2013, 12:51 PM   #1
mfjoker
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Hello,

I am reading J. Palmer How to brew and here is what he says about this issue:

Re-hydrating Dry Yeast
Put 1 cup of warm (95-105F, 35-40C) boiled water into a sanitized jar and stir in the yeast. Cover with Saran Wrap and wait 15 minutes.
"Proof" the yeast by adding one teaspoon of extract or sugar that has been boiled in a small amount of water. Allow the sugar solution to cool before adding it to the jar.

but a bit after that we see such words

After the boil, the wort must be cooled to yeast pitching temperature (65-90 F [18-32 C]) as quickly as possible

So here comes the question: Is 95-105F, 35-40C temperature comfortable for yeast? Won't it kill yeast? Or we will be adding almost dead yeast to teh wort?

Have a nice brew day



 
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Old 03-19-2013, 12:58 PM   #2
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Read the manufacturer spec sheet most yeast prefer 80 degrees to 100 when rehydrating


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Old 03-19-2013, 01:02 PM   #3
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Reading manufacturer's PDF's,I see 90-105F more often than lower temps. I've rehydrated in 75-80F water,& found that 90F water works a bit more vigorously. I also rehydrate covered for 30 minutes. The critical step,however,is cooling it down to within 10 degrees of current wort temp so as not to shock the yeast with a larger temp differential. This keeps the yeast healthy & makes for a more vigorous initial fermentation.
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Old 03-19-2013, 01:02 PM   #4
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Yeast is fine there, absolute drop dead high temp for yeast is appx. 140F. Our yeast friends are great survivors, after all in the wild they survive temperature swings from -10F to 110F+, weeks below freezing, weeks above 100F, etc.
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Old 03-19-2013, 01:07 PM   #5
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I'd just cool the wort to 70f or lower and pitch the yeast straight into the fermenter. I've tried rehydrating vs just pitching right out of the packet and it really makes no difference. Other than having to do an extra step.
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Old 03-19-2013, 01:12 PM   #6
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It won't make any visible difference,I've found,if the rehydrated yeast isn't cooled to within 10 degrees of wort temp. This has the effect of pitching dry yeast,since the yeast shocks. Being at 85-90F & going into,say,65F wort will def shock them. It slows down the reproductive phase right before visible fermentation begins.
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Old 03-19-2013, 01:30 PM   #7
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Thanks for the quick answers

 
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Old 03-19-2013, 08:28 PM   #8
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Quote:
Originally Posted by unionrdr View Post
Reading manufacturer's PDF's,I see 90-105F more often than lower temps.
I am not sure what yeast you are using, but both US-05 and S-04 call for 80* +- 5. Regardless, it is always better to check the specs than to blindly use one temperature for all yeasts.
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Old 03-19-2013, 08:31 PM   #9
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Whew,boy,can't remember all of them,but I did find it on many yeasts I've used or wanted to use. I look them up on midwest. They're all not the same obviously,but many of them said about the same. and yes,I do agree to always look at the manufactures' PDF's.
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Old 03-19-2013, 08:50 PM   #10
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There's a legit reason to rehydrate dry yeast in warm tap water. I use 100*F +/- 5* water (based on the dry yeast studies done by Dr. Cone) whether using Fermentis or Danstar and have been pleased with the very consistent results.

I also, prior to pitching, lower the temp of the yeast slurry to within 10*F of the wort by adding small amounts of wort, stirring, letting it sit a few minutes and repeating as needed. Usually 3 wort additions into the Pyrex cup gets it cool enough.

This allows the dry yeast cells to rebuild their cell walls before you chunk them into the wort. A significantly larger percentage of them survive and you'll achieve a higher cell count.



 
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