[Robert]

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.

[BrewBama]

I saw this and thought hmm, I’ve not noticed any tartness but I can check pH.

I just took a sample of an Alt fermented with 1st gen K-97 as I transferred to keg and would love to add a data point for you. ...but my pH meter seems to have gone South for the Winter.

Nothing to see here — except frustration. LOL


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[Iliff Ave]

Very interested in this. I have a vienna lager with M84 that seems to exhibit this. Last night I had one and was thinking to myself, 'this is pretty good but I don't know what that tartness is'. I used the second generation on a Marzen so am curious to see if it's different.

I never cared for k97 because it was unusually tart to me but I never went past one generation. 

[denny]

Rob, what yeasts have you noticed this with?  I quit using Nottingham many years ago because of tartness, but I didn't have a pH meter back then to check with.

[dmtaylor]

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.

Excellent observation!!!!  I have been using mostly dried yeasts for several years now, and I have long noticed that they all seem to have the odd tartness.  I've always used fresh packs, not repitched.  I thought maybe I just didn't like dried yeast?  But if your observation is correct, then perhaps I should check pH, and perhaps we should all be making yeast starters for all dried yeasts!!!!!  Then it would always be "re-pitched", at least from the starter to the intended wort.

Fantastic.... why didn't we think of this before?!  Over the next few days I'll measure the pH of some of my finished beers, and see how they compare.  I've got several batches to choose from.  Easy enough to pull out the old pH meter (which yes, I do calibrate for EACH AND EVERY USE).

EDIT:  To answer Denny's question, I get a very peculiar tartness from WB-06 for certain.  Swore I'd never ever use that yeast again.  I still have a couple bottles of that one and will report back on exact pH reading.

[The Beerery]

I get weird stuff from all dry yeasts, which is why I don't use them. I have noticed low pH, lemon, bleh.

[Robert]

Denny, Nottingham and S-04 are definitely major culprits IME.  I have found  very low first gen pH and tartness) with those two,  but normal thereafter. I think other yeasts show it in varying degrees.

Dave, this is exactly where my train of thought is going -- a
decanted  starter/propagation could be just the thing!  I've never tried it but it would be a great experiment. The initial convenience of dried yeast over liquid as a new pitch would be lost.  But if dry yeast is your only viable source, as I know it is for many who don't have a reliable LHBS, then it's quite reasonable.  It would be better than having abnormal fermentation and flavor on every new pitch.   If you try it, please report.  (I just got a pitch of a particular liquid culture which I plan to run for a few batches, so it will be a while before I get the chance.)

I'm still curious -- especially knowing I'm not alone in this -- whether any microbiology experts could identify why this happens. 

[dmtaylor]

WB-06 German hefeweizen is at pH 3.7.  It is too tart for my liking, not a horrible beer but zero clove or banana which is dumb.  It does have a slight chlorophenol, which is odd since I'm sure I used Campden, I always do, but that's the only phenol I get out of this.  Not my best hefeweizen, that's for sure.  But I remember being struck by the tartness the first time I ever tasted it, and today was no exception either.  Tart.  Can drink it, it's alright, but not a very good German hef.  So yeah, I won't be using WB-06 anymore.  But maybe for an American hefe, after second use and not fresh from a new pack of yeast, it might be okay!   

[goose]

This is an excellent topic!  I have never measured the pH of my finished beers but am going to start to do so.  At least it will give some data points that we can all look at.
For the record, I almost always used liquid yeasts.  I know starters tend to be a PITA, but I have always liked the results I have gotten from them.  In a pinch, I will sometimes use S-05 when I can't get to my LHBS before a brew day.  I will also keep track of tartness when I use them as I almost never re-pitch.  I just don't brew enough to make that a viable option.

[Robert]

I love this forum.  Glad to know there's interest in pursuing this.  For further clarification of my methods and what I've so far compared:  Dry yeasts have all been direct pitched, no rehydration or aeration;  that's what Fermetis and MJ recommend, and Lallemand yeast seems to respond just the same.  Repitched yeast was treated as I would any repitch: slurry stored under beer, used within 5 days, aeration as usual.  I've not tried rehydration or a starter to see if that leads to a more normal fermentation and pH in the first generation.  And it would be nice to have corroboration of my observations about repitching vs. first generation.

At some early point the value of record keeping was impressed on me.  So from mashing in to packaging,  every time I pull a sample I record four parameters: time, temperature,  gravity and pH.   Asked why, I've said "just so I know things are going normally, or not."  Guess it's been worth it.

[joe_meadmaker]

Like Goose, I also use liquid yeast almost exclusively.  So I don't have any personal experience to add to this discussion.  That said, I agree this is a fascinating topic.  It sparked a memory of a Brulosophy article on rehydrating dry yeast vs not.  It's here if anyone wants to check it out: http://brulosophy.com/2014/09/15/sprinkled-vs-rehydrated-dry-yeast-exbeeriment-results/

I pulled it up and read through it again.  In the two batches Nottingham yeast is used.  In the discussion at the end, it is stated that the batch made with non-rehydrated yeast had a "subtle apple-like tartness".  Although it doesn't appear that this flavor was something most of the taste-testers were able to detect and/or identify.  Definitely interesting.

[Robert]

 

Like Goose, I also use liquid yeast almost exclusively.  So I don't have any personal experience to add to this discussion.  That said, I agree this is a fascinating topic.  It sparked a memory of a Brulosophy article on rehydrating dry yeast vs not.  It's here if anyone wants to check it out: http://brulosophy.com/2014/09/15/sprinkled-vs-rehydrated-dry-yeast-exbeeriment-results/

I pulled it up and read through it again.  In the two batches Nottingham yeast is used.  In the discussion at the end, it is stated that the batch made with non-rehydrated yeast had a "subtle apple-like tartness".  Although it doesn't appear that this flavor was something most of the taste-testers were able to detect and/or identify.  Definitely interesting.

I've always been exclusively liquid, real dry yeast noob, maybe that's why this jumped out at me.  Hundreds of batches behaving similarly, and then suddenly an unexpected effect. Too bad Marshall didn't record pH data.  But the tasting data is interesting.

[Robert]

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.

[BrewBama]

Robert, have you cleaned your kegs with the milkstone remover?  If so, did you rinse really well afterwards? Just reaching for straws here.


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[Robert]

Oh, it's absolutely not equipment related.   Good thought though!  (One might suspect you'd had a career involving troubleshooting systems... oh you did.  Thanks for your service.)  As noted, I keep good records.  I know what a normal fermentation record looks like,  and what's interesting is that the same yeast, in the same conditions,  behaves differently in first and subsequent generations.   Which, with respect to this parameter, does not occur with liquid cultures,  IME.  I have a fairly small number of data points, but enough to establish a clear pattern, raise a red flag, and suggest a hypothesis, or I wouldn't have started this thread; I haven't found a confirmed exception.  Before I decided to explore for myself the possible advantages of dry yeast,  I'd noticed plenty of mentions on the forum of tartness with dry yeast.   I realized that my habit of monitoring pH, and reusing yeast, might have peeled back  a layer others hadn't noticed.  What I lack is the ability  to identify a likely mechanism, and remedy.  Forgive me if I'm rambling.  The practical assessment of product is going well.