General Category > Yeast and Fermentation

Don't make yeast starters from dry yeast? WTF?

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bluesman:
I have to agree with the yeast experts here. Making a starter with dry yeast is not recommended, as it will only deplete the glycol reserves much needed for anaerobic metabolism. Rehydration of the dry yeast is recommended as it allows for rehydration and mitigates destruction of the cell walls during the process.

Dry pitching the yeast will kill a significant percentage of the cells during the rehydration process, because the sugar concentration in the wort has a toxic effect on the yeast. The cell walls are not able to effectively absorb wort. Rehydrating in warm water first allows for a much better potential of survival during fermentation.

a10t2:
Glycol probably isn't great for the yeast anyway. ;)

bluesman:

--- Quote from: a10t2 on January 31, 2013, 06:40:50 PM ---Glycol probably isn't great for the yeast anyway. ;)

--- End quote ---

Only on Sundays. ;)

jackhorzempa:

--- Quote from: dimik on January 28, 2013, 07:54:12 AM ---I didn't see anyone bring up the main issue (in my opinion). Which is if you make starter with dry yeast, you'll kill about 50-60% of them right off the bat. It is better to rehydrate dry yeast in warm water (35-40*C - 95-104*F) for 15-20 min and then gradually cool and add to wort or starter. This has to do with the fact that dried cells have damaged membranes and need time to rebuild them, "patch the holes", resume membrane transport control, etc. Otherwise they have no control as to what goes in or out of cells. That happens fairly quickly, but still takes a few minutes. Temperature also plays a role. Rehydrating in cool water ~60*F will usually kill about a half of them. Now if you put dry yeast into a starter, the relatively high sugar concentration (yes, even 1.030 is high relative to dry yeast) and hops (if any) will destroy a lot of cells so essentially you'll be raising the starter to get back up to the number of cells that was there to begin with.
Another thing is that dry yeast packets contain approx 200 billion cells, and if you put directly into wort and kill half of them in doing so, there will still be enough cells left to normally ferment your average beer.

--- End quote ---
I think you made an excellent point. Making a starter with dry yeast is indeed detrimental since a lot of the yeast cells will be killed in the process!

Cheers!

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