Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Dry yeast. Should I rehydrate?
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Old 06-30-2011, 02:45 AM   #11
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yes rehydrate. the potential upside is twice the yeast cell count, the potential downside is introduction of bugs if your hydration process is unsanitary. (Chris White and Jamil Zainasheff, Yeast 146-148)

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Old 06-30-2011, 03:08 AM   #12
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Old 06-30-2011, 03:16 AM   #13
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I rehydrate because Fermentis says to if pitching below 20 degrees C, which is always the case for me.
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Old 06-30-2011, 12:18 PM   #14
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Originally Posted by Revvy View Post
Fermentis wouldn't suggest what they suggest if dry yeast spontaenously just committed suicide because we didn't rehydrate.
Sure they would. Just put more yeast in the pouch. It makes it easier for the ultra beginner or I-will-only-brew-beer-if-it-has-two-steps brewer. Many (less these days) packs of dry yeast end up taped to the top of cans of LME in kit-and-kilo beer kits. People that make these kits don't want the extra steps, and the manufacturer doubts that if they included these extra 5 steps people do it right if at all.

From Yeast by White and Zainasheff:
Skipping rehydration kills about half the cells pitched. .... Why would anyone recommend skipping rehydration? For the same reason you would avoid making a starter: Your process is either unsanitary or damaging to the yeast health.
This is not just speculation. This is based on actual experiments where yeast was rehydrated and counted. That's right, with a microscope.

Later, talking about what to rehydrate in...
Ideally, the mineral content should range from 250 to 500 parts per million hardness. During the first moments of rehydration, the cell cannot regulate what passes through the membrane. High levels of sugars, nutrients, hop acids, or other compounds can enter freely and damage the cells. This is why adding dry yeast directly to the wort results in such a high percentage of dead and damaged cells.
So how can this be? All the people Revvy quoted above didn't rehydrate their yeast and their "beer came out fine." So maybe the debate should not be about whether or not skipping rehydration kills yeast, but rather, what constitutes a "fine" beer.

So for me, if I can do or recommend something that is so simple and costs next to nothing and stacks the cards in my favor of making great beer, this is what I am going to do and recommend.

(Aside: this is essentially the same "debate" as making a starter. The tube/pack says "pitch 1 tube" yet everyone here knows that make a proper starter to grow the cells to the proper number of yeast is going to result in a healthier fermentation and potentially a better beer.)
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Old 06-30-2011, 12:28 PM   #15
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i've noticed shorter lag times if i didn't rehydrate (in a separate container). of course maybe this is for other reasons, but on several occasions i had the same result.
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Old 07-03-2011, 04:21 PM   #16
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I am by no means a pro brewer or have a PHD in yeastology so you can take this for what you want. I have just tossed in dry and have had good luck and I have rehydrated with good luck as well. Now the way I have rehydrated probably differs from anyone elses method since I have searched and searched and not seen anyone really talk about this. I do 5 gallon extract batches boiling 3 gallons and mixing the other 2 gallons in the fermenter. A few minutes before I stop the boil I pour in 1 gallon of my bottled water into the fermenter and then toss my dry yeast in with it. I let it sit for about 15 or so minutes while my chiller is doing its job. After it has sat for about 15 minutes I swirl around the yeast water mixing it all up. When my wort is chilled and before I pour it in the fermenter I swirl really good again. Pour in my wort swirl again and add the last gallon and swirl again. So far I have had really good ferments doing this and have even had a major blow off. Works for my lazy self so far. Just did a batch last night doing this method and it was doing the bubble dance like mad when I woke up this morning.
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Old 07-03-2011, 05:20 PM   #17
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Also by this write up, when rehydrating yeast temperature is very important also. The author advices you will kill up to 60% of your yeast if you do not rehydrate with the right temperature water.

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