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Old 07-03-2013, 07:33 PM   #1
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Default Yeast - sprinkling verse rehydrating

I currently have a helles (or it may be a Dunkel) in the fermenter - bubbling nicely thanks to some Saflager 34/70 that i sprinkled into the primary once the temperature was right.

I did a lot of reading about that yeast and read stacks of advice on how you should rehydrate the yeast, how to use it to make a yeast starter... Fortunately I also found quite a few people who had success a few times by just sprinkling the yeast granules into the wort directly.....which is what the directions on the pack say.

If a yeast is going to work (like it has) if you simply sprinkle the granules in, what are the advantages of rehydrating or preparing a starter? Is it worth the risk? Is it worth diluting the wort you work so .......... hard to produce?

This question is specifically about yeasts where the manufacturers (if that's the right word) suggest sprinkling the yeast in. I know it doesn't work for all yeasts.

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Old 07-03-2013, 07:34 PM   #2
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You get a faster start to fermentation if you rehydrate. Faster start means less time for baddies to infect.

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Old 07-03-2013, 07:50 PM   #3
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First, I'm no expert so someone a lot more knowledgeable and experienced ought to come along and offer an excellent answer to this question. But I'll take a stab at it anyways.

Reydrating and making a yeast starter are two different things. The idea of a yeast starter, and if I'm not mistaken is only usually done with liquid yeast (?) is to introduce the yeast to malted barley sugars so that they have significantly multiplied in order to 'hit the ground running' when they're introduced into our wort. I can't quote the magnitudes of multiplication they undergo by doing a starter several days before hand, but I believe it's quite high. Since the starting solution you're using is basically 'wort', you're not really watering your intended wort down when you pitch the starter into it.

Rehydration is basically awakening dormant dry yeast in a warm water bath and then bringing it to pitching temperature to coincide with the pitching temp of your wort. The amount of water is extremely negligeable. Why this is that much better than pitching the yeast dry is a good question, and I'm guessing that it has to do with not shocking the yeast in one way or another. But exactly what way that is... I'm going to watch this thread further to find out...

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Old 07-03-2013, 08:05 PM   #4
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Per Chris White in the Yeast book, you can kill quite a bit of the yeast by not re-hydrating dry yeast. Starters are more for growing up more yeast to be pitched.

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Old 07-03-2013, 08:11 PM   #5
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I think what andy said is on the right track, and I am also no expert in yeast studies or biology

Starters are usually only liquid yeasts because dry yeasts are said to have those essential components already built into them at the labs (sterols and other fancy stuff), that provide the yeast the components for reproduction and healthy fermentation. A starter has difference levels of multiplication depending on many variables (available oxygen, exposure to the sugars, temperature, volume of liquid, length of time allowed to multiply, etc), but generally speaking you're looking at about 1.5x-3x the population of what you pitch into the starter. Most starters are crash cooled (i.e. cooled in fridge) for a day or two to get the yeast to drop to the bottom, and then 95% of the liquid is poured off down the drain before pitching the actual yeast into the batch of beer. However, pitching a relatively small volume of starter sans crashing is also acceptable and may be beneficial in some instances where you're trying to restart a stalled fermentation (i.e. pitching at high krausen).

Rehydration: In addition to awakening the yeast and bringing to warm temperatures, you are rehydrating the yeast's cell walls using a gentle and proven medium that causes little stress to the yeast (i.e. sterile water). This way, when they are tossed into the much harsher environment (wort) they have a good cell wall to prevent instant damage associated with sudden change (pressure changes on the cell wall). At least that's my current understanding of it....

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Old 07-03-2013, 08:25 PM   #6
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Quote:
Originally Posted by stpug
Rehydration: In addition to awakening the yeast and bringing to warm temperatures, you are rehydrating the yeast's cell walls using a gentle and proven medium that causes little stress to the yeast (i.e. sterile water). This way, when they are tossed into the much harsher environment (wort) they have a good cell wall to prevent instant damage associated with sudden change (pressure changes on the cell wall). At least that's my current understanding of it....

This nails it on the head. It's all about protecting those cell walls. You can survive with just sprinkling but you will probably not get the attenuation that you are looking for and end up with a lot dead yeast cells on the bottom of your carboy. Another reason the dry yeast websites always say to rehydrate in the pro brewers sections.
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Old 07-03-2013, 10:57 PM   #7
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Here's a better explanation than I could ever give from a real yeast expert - http://koehlerbeer.com/2008/06/07/re...-clayton-cone/

The reason that folks who just sprinkle often get away with it is because of the large number of cells in an 11g packet of dry yeast. I rehydrate because I want as many viable cells in there as I can get, especially for a lager.
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Old 07-04-2013, 01:02 AM   #8
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The takeaway is that by NOT rehydrating dry yeast, you are effectively killing half of your yeast, defeating one of the major purposes of using dry yeast (higher cell count per package).

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Old 07-04-2013, 07:33 AM   #9
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Thanks for all these replies and suggested links. I will take a look.

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Old 07-04-2013, 09:46 AM   #10
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Depends on the gravity reading of the wort. In a low gravity wort, more water for the yeast to absorb.

Rehydrating the yeast is good if u have a big beer.

Many people have reported no major changes in the final outcome of the beer in rehydrating vs not (mainly testing on side by side comparison of fermentation).

In theory, rehydration is the best option. I just go by what the packet states to do.

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