Author Topic: Dried yeasts and pH  (Read 3167 times)

Offline Robert

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Re: Dried yeasts and pH
« Reply #15 on: October 24, 2018, 12:33:16 AM »
Sampled another 2d gen today.  Nottingham.   1st gen finished at pH 3.78, 2d gen 4.2, with no tartness,  nice balanced flavor.
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Offline Joe Sr.

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Re: Dried yeasts and pH
« Reply #16 on: October 24, 2018, 02:59:44 AM »
Like Denny, I gave up on Nottingham ages ago due to the tartness. I don't recall tartness with other dry yeasts but I have no reason to doubt your experience. I could check my notes from back in the day. Haven't used dry yeast in a long time.


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Offline ynotbrusum

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Re: Dried yeasts and pH
« Reply #17 on: October 24, 2018, 11:13:52 AM »
Great discussion.  I use a fair amount of dried lager yeast and routinely rehydrate, as it seems to cut the lag time I otherwise experience with dried yeast.  I also repitch on a regular basis.

I happened to use first gen Nottingham in a dry stout batch that is now ready to keg, so I will sample for tartness - I rehydrated it, FWIW...
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Offline Joe Sr.

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Re: Dried yeasts and pH
« Reply #18 on: October 24, 2018, 03:52:23 PM »
Great discussion.  I use a fair amount of dried lager yeast and routinely rehydrate, as it seems to cut the lag time I otherwise experience with dried yeast.  I also repitch on a regular basis.

I happened to use first gen Nottingham in a dry stout batch that is now ready to keg, so I will sample for tartness - I rehydrated it, FWIW...

I've always rehydrated dry yeast and it did not seem to have an impact on the tartness.

I'm pretty sure I've repitched Notty in the past, but have no specific recollection of the tartness being there or not on a second gen.

I used to use dry yeast, and in particular Notty, pretty regularly.  It got to the point where I was noticing the tartness so much I had to go back and check my notes on beeers and the yeast was the common thread on each.  I was afraid I had some sort of infection, but nope, just Nottingham.

I do not own a pH meter, so that's something I have never checked. 
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Offline hulio555

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Re: Dried yeasts and pH
« Reply #19 on: October 24, 2018, 04:24:05 PM »
I have been trying dried yeasts a fair bit of late, and have noticed something interesting.  The first generation fermentation finishes with an unusually low pH,  around 3.8, with (unless I'm deceiving myself and tasting what I expect to find) a predictable slight tartness in the beer.  On harvesting and repitching the yeast, subsequent generations seem to perform just like normal liquid cultures, with a finished pH of around 4.2.  Can anyone explain this?

Possible exceptions are W-34/70 and Windsor,  both quite powdery; but this may well be a red herring or just an outlier,  because I'm reporting only a nearer-normal first generation pH, having made no comparison with a repitch.
The problem with dry yeast is it is contaminated with non-yeast microbes, if yeast grows faster than bacteria (lactos) there would be more of it in future generations. leaning out the effect of lower pH caused by the smaller % of lactic acid producing microbes. one possible reason.
« Last Edit: October 24, 2018, 04:26:53 PM by hulio555 »

Offline BrewBama

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Re: Dried yeasts and pH
« Reply #20 on: October 24, 2018, 04:45:27 PM »
The problem with dry yeast is it is contaminated with non-yeast microbes, if yeast grows faster than bacteria (lactos) there would be more of it in future generations. leaning out the effect of lower pH caused by the smaller % of lactic acid producing microbes. one possible reason.

Sounds plausible.


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Offline Robert

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Re: Dried yeasts and pH
« Reply #21 on: October 24, 2018, 05:32:03 PM »
The problem with dry yeast is it is contaminated with non-yeast microbes, if yeast grows faster than bacteria (lactos) there would be more of it in future generations. leaning out the effect of lower pH caused by the smaller % of lactic acid producing microbes. one possible reason.
So if this hypothesis is correct,  rehydration should result in the same 1st generation pH as direct pitching,  but making a starter might make a difference.  Experiment needed.
Rob Stein
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Offline dmtaylor

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Re: Dried yeasts and pH
« Reply #22 on: October 25, 2018, 02:05:57 AM »
The problem with dry yeast is it is contaminated with non-yeast microbes, if yeast grows faster than bacteria (lactos) there would be more of it in future generations. leaning out the effect of lower pH caused by the smaller % of lactic acid producing microbes. one possible reason.
So if this hypothesis is correct,  rehydration should result in the same 1st generation pH as direct pitching,  but making a starter might make a difference.  Experiment needed.

Or here's an easy one.  Campden kills bacteria, right?  So, just before pitching, add some Campden.  Pitch as normal.  The microbes should die but the yeast should survive -- some of the yeast anyway -- cultured yeast is much more robust than wild beasts.  Then ferment out as normal and check pH, yadda yadda.
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Offline goose

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Re: Dried yeasts and pH
« Reply #23 on: October 25, 2018, 01:41:57 PM »
Some ignorant musings of an amateur, trying to work through stuff a bit over my head.

I know most of the pH reduction occurs very early on, and this is crucial to a healthy fermentation.   The majority of organic acid production, as I understand  it, occurs during the anaerobic repressed fermentation phase.  Could dried yeast,  by bypassing the earlier aerobic (I said aerobic,  not respiratory,  so don't go all Crabtree on me) phase  and proceeding straight to anaerobic metabolism, have more opportunity for acid production?   In which case the making of a starter, run to completion and decanted,  might just do the trick?   I wonder if some part of the excess acidification might be a stress response (shock excretion,) which might be alleviated by rehydration.   But a starter would address either mechanism.   Help with this welcome.   Anyway.  Enough of the books for this evening,  time for a practical assessment of the end product.

Another observation based on Rob's post here.  When i used dry yeast, I always pitched directly into the wort as recommended by Fermentis and always had relatively short lag times.  One of the locals here (who I brew with a lot) said that he always re-hydrated his dry yeast to reduce the number of dead cells in the pitch caused by shocking the yeast in a high sugar environment.  I tried it the very last time I used US-05 (had to because I could not get 1056 before my brew day) and had a lag time that way too long.  I had to do the hubba bubba to get a couple more packages and re-pitch (did not re-hydrate them) to get the beer started.  Obviously, this was the very last time I used dry yeast.
This may have been operator error here.  I did make sure that I cooled the re-hydrated yeast in a covered glass measuring cup to within about 7 degrees of the cooled wort temperature to avoid thermally shocking the yeast.  Never did figure out what happened, so I have chalked it up to operator error.

This has been an excellent discussion topic and has led me to record more data points on my beers as they are fermenting!
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Offline ynotbrusum

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Re: Dried yeasts and pH
« Reply #24 on: October 25, 2018, 08:35:32 PM »
When I rehydrate, I usually do so in my fermentation chest, so it is chilled and being pitched into the same or warmer wort once I pitch....again these are lagers, but I do the same for some ales that I start on the colder side for initial fermentation.
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Offline BrewBama

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Re: Dried yeasts and pH
« Reply #25 on: October 25, 2018, 09:50:17 PM »
If you choose to use 2nd gen dry yeast, yet only brew once a month or so, how do you properly store your yeast for that long without fear of it degrading?


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Offline Joe Sr.

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Re: Dried yeasts and pH
« Reply #26 on: October 25, 2018, 10:01:17 PM »
If you choose to use 2nd gen dry yeast, yet only brew once a month or so, how do you properly store your yeast for that long without fear of it degrading?


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Not specific to 2nd gen dry yeast, but I keep slurry in rubbermaid containers in my beer fridge.  When I want to brew, I take out the slurry and build a starter.  90% of the time the starters are good.  Occassionally, I toss one.  If the slurry sits too long, I toss it and start fresh.
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Offline BrewBama

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Dried yeasts and pH
« Reply #27 on: October 25, 2018, 10:32:55 PM »
Thanks Joe Sr. How long is ‘too long’? 

Edit: I’ve read “If less than two weeks, brewers will usually have no problem reusing yeast. Over two weeks and you may or may not have problems. After four weeks, the viability of yeast slurry is usually 50% or lower. As yeast sit in storage, they consume their glycogen reserves.”

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« Last Edit: October 25, 2018, 10:35:39 PM by BrewBama »
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Offline Robert

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Re: Dried yeasts and pH
« Reply #28 on: October 25, 2018, 11:20:24 PM »
I'm not Joe, but... First the disclosure,  I can't remember the last time I reused any yeast more than 5 days after harvesting,  but I know I used to do it with no problem.   We homebrewers have a distinct advantage over the pros. A little yeast in a temperature controlled, 5-10 gal fermenter is not subject to the same hydrostatic pressure and heat buildup as in the cone of big fermenter,  so it can be much healthier at harvest than advice based in commercial practice might suggest,  and likewise will store better in a small jar in the fridge than in the cone or a brink.   Most yeasts should be good to just directly repitch at least two weeks out.  Just pitch a little more than you normally would to make up for non viable yeast and non yeast material.   If you're at all concerned,  make a starter.  And remember the best medium for storage is the beer the yeast fermented.  Don't rinse,  that raises the pH making it more vulnerable to bacteria,  and introduces oxygen which may accelerate glycogen depletion.   (Come to think of it, back in the day I did rinse, and let it sit for weeks, and it was still good.  But don't do that.) 
Rob Stein
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Offline hulio555

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Re: Dried yeasts and pH
« Reply #29 on: October 25, 2018, 11:23:20 PM »
The problem with dry yeast is it is contaminated with non-yeast microbes, if yeast grows faster than bacteria (lactos) there would be more of it in future generations. leaning out the effect of lower pH caused by the smaller % of lactic acid producing microbes. one possible reason.
So if this hypothesis is correct,  rehydration should result in the same 1st generation pH as direct pitching,  but making a starter might make a difference.  Experiment needed.
which may be why every dry yeast manufacturer suggests that we rehydrate and every advanced brewer suggest an appropriate starter size