From the HBD Archive
From: Pete Soper <soper@maxzilla.encore.com>
Subject: Dried yeast
Date: 1989-09-22 14:37:24 GMT

In HBD #261 roberts%studguppy@LANL.GOV (Doug Roberts) writes:

>To quote (Williams Brewing catalog):
>> "It appears most home brewers have been abusing their
>> dry yeast. Dry yeast should only be rehydrated in warm
>> water between 90 and 100 degrees F. Use 1/2 cup of
>> water for every 14 grams of dry yeast. Rehydrating
>> dried yeast in wort can shock and injure the yeast,
>> because wort is relatively acid,and dry yeast prefers
>> a neutral rehydration medium. It is vital to the
>> future flavor of the beer that dry yeast be rehydrated
>> in warm water only.

>> Ideally, rehydration should take place for 15 minutes
>> before pitching. When pitching, it is very important
>> that the freshly revived yeast is not temperature
>> shocked; a temperature change of more than 17 degrees
>> will cause the yeast to both emit off-flavor compounds
>> and slow down, perhaps halting all activity if the
>> shock is great enough. If your yeast is at 90 degrees
>> F. and your wort is at 65, add a half a cup of wort to
>> your yeast to become acclimated to the new
>> temperature, and then pitch into the 65 degree
>> fermenter."


>90 to 100 degrees sounds awfuly high to me. I would be real hesitant
>to plunk my yeast into water that warm. 70 to 80 degrees, maybe, but
>temperatures above that are in contradiction to everything I've ever
>read about beer yeast.

But the point of this part of the article is that some of what we've
all read is not based on proper handling of yeast cells, specifically,
bombarding their cell walls with sugar molecules before they are ready
to handle them and not paying proper attention to temperature management.
Many dried yeasts have instructions written on their packets that
specify just the kind of hydration procedure described by Williams above.
(I included some more of the Williams' quote so folks that only see
this message have the essential subset of information)

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