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BMBARON 01-29-2012 08:47 AM

Rehydrating yeast
 
Should i rehydrate the yeast that comes with a home brew beer can before i pitch?

1Mainebrew 01-29-2012 09:43 AM

Yes, the yeast is shocked and can lyse apart with the sudden rehydrating in sugary wort. Rehydrate first or you'll lose about half of the cell count right out of the gate.

BMBARON 01-29-2012 07:37 PM

Ok so what's involved in rehydrating your yeast how do you do it ?

SC_Ryan 01-29-2012 09:10 PM

Boil about a cup or two of distilled water for 5-10 minutes, you will need 4oz of water per packet of dry yeast. Keep in mind some will boil off. It's ideal if you can put a tiny pinch of gypsum or calcium chloride in the water before you boil it. The yeast like the calcium. When the water cools down to 80-90* add the yeast packet to 4oz of the water and let it sit. Do not stir. Once the concoction has cooled down to about 70* you can stir it up and pitch it in your wort.

ChillWill 01-29-2012 09:23 PM

Quote:

Originally Posted by SC_Ryan
Boil about a cup or two of distilled water for 5-10 minutes, you will need 4oz of water per packet of dry yeast. Keep in mind some will boil off. It's ideal if you can put a tiny pinch of gypsum or calcium chloride in the water before you boil it. The yeast like the calcium. When the water cools down to 80-90* add the yeast packet to 4oz of the water and let it sit. Do not stir. Once the concoction has cooled down to about 70* you can stir it up and pitch it in your wort.

Don't use distilled water! Unless you add the minerals you suggest.

You get osmotic shock by using distilled, but instead of the cell walls letting in too much sugar, you get the interior of the cell trying to move to the lower density solution (the distilled water).

A 50:50 wort:water mix can also be used.

biestie 01-29-2012 09:35 PM

Quote:

Originally Posted by ChillWill

Don't use distilled water! Unless you add the minerals you suggest.

You get osmotic shock by using distilled, but instead of the cell walls letting in too much sugar, you get the interior of the cell trying to move to the lower density solution (the distilled water).

A 50:50 wort:water mix can also be used.

Can you provide a source for this? Not saying you're wrong, I just haven't heard that.

Droot 01-29-2012 09:39 PM

I proof my yeast, then I know its good. It gives it a good start.

David

RM-MN 01-29-2012 09:42 PM

Different manufacturers have different info on rehydrating dry yeast. Some say it is really important while others say you don't need to at all. YMMV

ChillWill 01-29-2012 09:54 PM

Quote:

Originally Posted by biestie

Can you provide a source for this? Not saying you're wrong, I just haven't heard that.

A scientist/project leader who previously worked at lallemand told me while in a lab session with commercial brewers from my part of the country.

It makes sense if you about the definition of osmosis:
"The movement of a lower density solution through a semi-permable membrane to a solution of higher density". Or something like that.

Basically, it works both ways. Until the cell walls are built up, using the hydrogen bonds of water to 'reorganize' them, the cells can't control what goes in or out so you don't want a high density solution such as wort, or too low such as distilled/RO water.

osagedr 01-29-2012 10:09 PM

Quote:

Originally Posted by BMBARON (Post 3718856)
Should i rehydrate the yeast that comes with a home brew beer can before i pitch?

What kind of yeast is it? I always rehydrate my dry yeast and have actually started doing it in a "stirred vessel" (i.e. glass measuring cup with a small stir bar on my stir plate). I've copied what Fermentis has to say on the matter and pasted it below (from the S-04 product sheet):

"Re-hydrate the dry yeast into yeast cream in a stirred vessel prior to pitching. Sprinkle the dry yeast in 10 times its own weight of sterile water or wort at 27C 3C. Once the expected weight of dry yeast is reconstituted into cream by this method (this takes about 15 to 30 minutes), maintain a gentle stirring for another 30 minutes. Then pitch the resultant cream into the fermentation vessel.

Alternatively, pitch dry yeast directly in the fermentation vessel providing the temperature of the wort is above 20C. 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 and then mix the wort e.g. using aeration."


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