Author Topic: Temperature of dry yeast when rehydrating??  (Read 6688 times)

Offline cowboy up

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Temperature of dry yeast when rehydrating??
« on: January 20, 2009, 11:10:50 AM »
My access to liquid yeast is almost nil (unless I mail order it). Our local brew shop only handles dry yeast packets. My question is: on the back of a pack of Muntons dry yeast it says to rehydrate the yeast in a cup of cooled boiled water at a temp of 38-40 C. That equates to a temp of around 100-104 degrees! That sounds awful high to me, considering it is suppose to be pitched into wort that is under 80 degrees. Why such a big difference in temps? Why can't I pitch the yeast then at around 90 degree temp or less and still have good fermentation? At 90 degrees the yeast would start the fermentation sooner than if it was pitched at 80 degrees. I assume (and I know what they say about "ass-u-me") the higher rehydrating temp does not hurt the viability of the yeast, then why would it be a problem in the 90 deg. wort? What am I missing? Has anyone pitched at a higher temp than 80 deg.? Thanks Cowboy Up!!

Offline UselessBrewing

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Re: Temperature of dry yeast when rehydrating??
« Reply #1 on: January 20, 2009, 12:08:58 PM »
My access to liquid yeast is almost nil (unless I mail order it). Our local brew shop only handles dry yeast packets. My question is: on the back of a pack of Muntons dry yeast it says to rehydrate the yeast in a cup of cooled boiled water at a temp of 38-40 C. That equates to a temp of around 100-104 degrees! That sounds awful high to me, considering it is suppose to be pitched into wort that is under 80 degrees. Why such a big difference in temps? Why can't I pitch the yeast then at around 90 degree temp or less and still have good fermentation? At 90 degrees the yeast would start the fermentation sooner than if it was pitched at 80 degrees. I assume (and I know what they say about "ass-u-me") the higher rehydrating temp does not hurt the viability of the yeast, then why would it be a problem in the 90 deg. wort? What am I missing? Has anyone pitched at a higher temp than 80 deg.? Thanks Cowboy Up!!
You will find that the temps vary by strain and brand, I have seen them as low as 20C. Per Danstar:(http://www.danstaryeast.com/faq.html)
Dry beer yeast needs to be reconstituted in a gentle way. During rehydration the cell membrane undergoes changes which can be lethal to yeast. In order to reconstitute the yeast as gently as possible (and minimize/avoid any damage) yeast producers developed specific rehydration procedures. Although most dry beer yeast will work if pitched directly into wort, it is recommended to follow the rehydration instructions to insure the optimum performance of the yeast.

The volume of water (1cup) will cool down much quicker than 5.5G of wort. Which is why you don't want to pitch it into hot wort.

Cheers
Preston
« Last Edit: January 20, 2009, 12:11:34 PM by UselessBrewing »
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Offline SOGOAK

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Re: Temperature of dry yeast when rehydrating??
« Reply #2 on: January 20, 2009, 01:46:26 PM »
The only dry I've pitched is Safale US05 which is supposedly wyeast 1056 or WLP001. 

Anyway-It is 2x yeast cells of muntons.  I have done rehydrate and starter, just rehydrate, and rip and pitch.  It seems to not matter.  Naturally, the starter went off faster.  But another factor is temp after pitch.  The same yeast in similair gravity behaved totally different speedwise.

All said, I like the dry better.  But I know liquid has much more variety.

I bet your LHBS guy can special order just about anything
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