Rehydrating yeast

Yeast talk, turbo, bakers and specialised strains

Re: Rehydrating yeast

Postby Andy » Sat Apr 12, 2014 2:55 pm

OzKev wrote:Yeast DO NOT need oxygen during their reproduction phase (log phase). Yeast use oxygen in their lag phase in the preparation for reproducing, which rehydration plays part of.


whops- your right they dont need oxygen to multiply.

rehydrating them isn't the lag phase though. its purely plumping up the cell walls. they do nothing while in the water.
the lag phase occurs while in the wash- which is why the wash is needs to be oxygenated.
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Re: Rehydrating yeast

Postby Yummyrum » Sat Apr 12, 2014 7:35 pm

Well sorry guys ,I'm as confused as all fuck now :laughing-rolling: hope there's no Noobs reading this.

Seriously ...I am ..and I have been for at least 10 years that I've been making wines and distilling ....I feel like a dumb shit about all this

There's that talk of the aerobic phase and the anaerobic phase and hydrating and straight pitching and starters with orange juice and starters that should only use the medium that the yeast will ferment in .. :teasing-blah: :teasing-blah: :teasing-blah: :teasing-blah: .

So what about magnetic stirrers...in ...or out :angry-banghead:



Having vented....slightly....I have only had one failed ferment ....(a re-pitch and aeration restored )...and some slow to start ones :hand:...the rest,no worries
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Re: Rehydrating yeast

Postby SBB » Sat Apr 12, 2014 8:19 pm

So now the bloke who asked and a fair few other newbies are completely confused as you said yummy.
Original question was "Also I making a tpw 2moro and was wondering if I need to rehydrate the yeast. Lowans Bakers yeast."
Simple answer is NO you do not need to, chuck the yeast in let it float on top or stir it in, what ever tickles your fancy, then let the yeast do its thing.
That's all that's needed, keep it simple folks.
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Re: Rehydrating yeast

Postby Furynfear » Sat Apr 12, 2014 8:23 pm

If u think this is bad if u look on the brew forums the argument has been going on for over 8 months whether it needs to be done. I don't no if I'm allowed to post so let us no and I'll add the link
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Re: Rehydrating yeast

Postby MacStill » Sat Apr 12, 2014 8:28 pm

Furynfear wrote:If u think this is bad if u look on the brew forums the argument has been going on for over 8 months whether it needs to be done. I don't no if I'm allowed to post so let us no and I'll add the link


Dont bother with the link, they wont allow ours over there ;-)

Anyway

This is distilling not beer making, a whole different ball game..... there is no "need" to do starters/rehydrate, although you "can" if you "want" too :handgestures-thumbupleft:
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Re: Rehydrating yeast

Postby Andy » Sat Apr 12, 2014 8:34 pm

as long as the yeast gets in a wash that's not too hot it will work :teasing-neener:
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Re: Rehydrating yeast

Postby bt1 » Sun Apr 13, 2014 7:41 am

Fury's question was nailed in first reply for a Lowans...simple stuff.

Yum raised the issue of a EC1118 slow starter reckon that's been addressed as well. There's many areas of this hobby where you can put in a little more effort and get a better result. Sure "throw it in" works but how well it works is the issue here.

As to magnetic stirrers would depend on the yeast strain as it always does. Take a Lallemand Belle Saison dry beer yeast ... it specifically states no stirring due to yeast damage/viability. Two other Lallemand yeasts I use have extreme temps during rehydration an EDV46 for rums and the K1 for fruits need 40c ....not joking here. Wyeast2007 pitches directly at 12c is another example.

It's another case of do you do the minimum or strive for something better.... and there will be as many answers to that as there are distillers. Most AG beer ppl would value their yeast and yeast prep a little more and that's what we're seeing...the benefit of that extra effort and understanding.


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Re: Rehydrating yeast

Postby OzKev » Sun Apr 13, 2014 8:39 am

I think it also comes down to pitch rates, temperatures and desired flavor outcomes (esters). Things like Lowans we pitch a very high rate, and then we are running it at a higher temperature. Even if we lost 1/2 of the viable cells with 4 times the pitch rate we still have twice the final viable pitch rate. Then with the increased temperature it significantly reduces the lag period. Hence not necessarily the same need for rehydration. That's why a lager yeast needs to be pitched at twice the rate of an ale yeast. Then say an ec1118 we are reducing the pitch rate and temperatures, so hydration for yeast viability starts to become more significant. When yeast reproduces in the log phase it produces a lot of the byproduct esters, which add desired character. Compare to the beer world, most the time the yeast is a lot more expensive and the pitch rate is a lot less to allow these byproducts to be produced. Pitching 10g of Lowans, or 100g of Lowans into a rum wash will still both produce the final product. They will take different amounts of time to get there, and there will be a difference in taste. How much difference of that taste carries over from the still, and how much is removed in the heads will vary.

More viable yeast cells also reduce the changes of infections taking hold. I believe all worts are infected. Don't believe me, check out a yeast msds. From SafSpirits American Whiskey, Acetic acid bacteria: < 1 x 10^3 / gramme. Lactobacillus: < 1 x 10^4 / gramme. So it's acceptable for some trace to be in the product. Then when the fermenter is open to the air during filling etc, you will get some bacterial sources in there. So a higher pitch rate increase the good cells Vs bad cells count in our favor. As long as the level of infection is not detectable by our taste buds we have succeeded in our ferment.

Personally from my >20years experience in brewing I don't believe the loss from pitching yeast dry is anywhere near 1/2. I think it should say up to 50% loss. The kill rate would be from many things. Thermal shock due to difference in temperatures between yeast and wort, actual wort temperature, wort pH, wort O2 levels, wort nutrient levels, initial yeast health, yeast clumping, amount of damage to the cells due to strong stirring, there's probably more but these are just of the top of my head. Even a drop of Olive oil on the wort can make a change to the overall speed of the ferment.

Remember bad hydration techniques can kill more cells than pitching dry. The main killer is time, leaving it for an hour or so in pure water would most likely result in less viable cells that pitching dry.

For the record I don't rehydrate any of my yeast anymore. My rum, as discussed prior, has a good enough pitch rate for me to pitch dry. My whiskey using the SafSpirit American Whiskey yeast I create a light starter. All this is a mix 50:50 chlorine free water and the wort it will be pitched into, at approx 30c. Allow the yeast to warm up close to the starter temperature, stir the starter mix and sprinkle in the yeast. Within 30mins you should see activity, and since it has a food source it can happily commence fermenting and be left for hours until you are ready to pitch it. There is a separate debate about using starters at lower gravity than the target wort, but I won't get into that.

Hope this helps 8-}
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Re: Rehydrating yeast

Postby Furynfear » Sun Apr 13, 2014 4:09 pm

This is very OT, so apologies! But I'm on the phone & couldn't easily find a better thread to post it.
I found this in a wine site while reading about yeast nutrition. It could be relevant in general yeast health, but especially in high OG brews:

During fermentation the yeast membrane becomes affected by alcohol and becomes more and more permeable or “leaky” as the alcohol content increases. This makes it more difficult for the yeast to take up and retain nitrogen as the fermentation progresses. Making the yeast membrane stronger at the start of fermentation can reduce the permeability problem. This can be improved by the presence of oxygen, which enables the yeast to make more survival factors such as sterols and long chain fatty acids that protect the membrane.

From:
http://www.vintessen...mentations.html
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