Wort pH and Risk of Botulism

[Broothru]

So, 'tis the season to start planning the next 12 months of brewing sessions. Normally by this time of year I'd already have squirreled away a case or two of home canned starters for yeast propagation, or at least had a few left over to get an early bird brew session out before the Spring thaw if the weather allowed. This year however, I've been doing so much 'lockdown brewing' that my stash ran completely dry and I've had to resort to actually buying cans of Propper just to make it through 2020. Since I can't fire up the trusty pressure canner outdoors to make my own I've been searching other methods to restock my supply, free of harmful microorganisms.

My tool of implementation for this would be a Fagor-brand electric cooker/pressure cooker. Physically, the canning jars would fit. Pressure-wise, the unit only reaches a pressure of 9 psig, or a little more than .6 bar. USDA guidelines for pressure canning low acid foods to destroy botulism spores is to ensure a temperature of between 240F-250F for at least :10 minutes. At 1 bar, water boils at 250F (sea level), so I would never reach that temperature in the Fagor. Water at 9 psig/0.6 bar boils at 238F which is very close to the minimum temperature recommended for denaturing botulism spores, but close doesn't count for much when dealing with potentially deadly toxins. Although time is also a factor in the process of denaturing botulism spores, USDA cites 240F and below as insufficient to fully and safely denature all spores regardless of time.

It would seem as if this would prevent me from using this pressure cooker/canner, and yet there is a way around this 240F-250F minimum. The need to pressure can a food product is also dependent upon its acidity. High acidity foods are considered safe for canning in a standard water bath boiling at ambient sea level pressure (i.e., tomatoes @ 212F) if they have a pH lower than 4.6. Generally my pre-fermentation beer worts have a pH between 4.9~5.2. While I realize that pH is measured on a non-linear logarithmic scale, it would still seem to be simple enough to acidify starter wort from pH 5.2 to 4.6 or less with ascorbic or citric acid and thus create an inhospitable environment for botulism spores to propagate. Logically if I can safely package tomatoes at 212F and not worry about botulism because of their acidity, why not starter wort?

My methodology would be to start with sterilized jars and canning lids (cleaned, sanitized and "autoclaved" in a 275F oven for :30 mins.), mix in a pre-measured amount of DME for a 1.020 SG wort with boiling distilled water, cap and pressure cook for :20 minutes, and finally slow cool at room temperature until the lids seal. The only differences between this and my usual process of pressure canning in a 'real' pressure canner would be sterilizing the jars/lids and using distilled water instead of filtered tap water. Before I go through the process of actually wasting DME and distilled water on a fool's errand to determine pre-process pH and how much acid addition is needed to achieve <4.6 pH for a quart of wort, I'd like to hear any opinions of the safety or efficacy of this idea. Also, is there any drawback to using an acidic starter wort (pH ~4.6) when culturing yeast? Would phosphoric or lactic acids be better choices for acidification?

I'm not a chemist or microbiologist, so please be gentle with any condescending comments or thoughts about my general lack of knowledge . Thanks in advance!

 

[Qhrumphf]

As far as botulism goes, I think that makes sense. It's pretty common practice with kettle souring (pre-acidify to 4.5 prior to souring) since it suppresses more than just botulism. Practically I'd think the combo of both acidification and an almost good enough pressure cooking would do the job but when it comes to something potentially lethal anything above zero chance would give me pause.

As far as using it afterwards, I don't think it'd make a huge difference. When kettle souring sacch still ferments wort at significantly lower pH than we're talking about (though at that point it struggles). If we assume normal wort pH of 5.0-5.2, it's a much smaller jump to 4.5 than 4.5 is to 3.5 where many a kettle sour might start its fermentation. That said, ability to ferment doesn't necessarily mean good for propagation (though some do acid starters for yeast in sour brewing to acclimate), so again I'm not completely confident, but in this case not a safety issue.

 

[Vale71]

I'm not a chemist or microbiologist, so please be gentle with any condescending comments or thoughts about my general lack of knowledge . Thanks in advance!

My dear sir, your lack of knowledge is truly remarkable.

There, hope this was gentle enough for you.

Basically you're planning on achieving finished beer PH in your starter wort. While saccharomyces can certainly work its magic under these conditions (after all that's the PH beer achieves through the yeast itself) this is not really optimal for wort used for propagation. The initial drop in PH that already occurs in the log phase (and than taperes off during the fermentation phase) is actually beneficial to the yeast, especially if it was stored for a significant amount of time (i.e. not fresh). Through acidification of the wort yeast cells achieve an increase in intra-cellular PH as well which is optimal for yeast health. If wort already has the optimal PH this will not happen and this could mean a less than optimal starting point for the yeast. Add to this the reduced nitrogen levels that you'll have in autoclaved wort because of increased hot break formation and you might end up with a suboptimal culture medium for this yeast.

Of course you could remedy this situation by adding yeast nutrients before pitching (not before autclaving or you'll lose some of the benefit) and possibly by increasing your canned wort's PH back to around 5.0-5.2 also right before pitching for example with sodium bicarbonate additions. I'm assuming you'll decant your final starter step so that any added minerals will not make it into the fermenter.

 

[Broothru]

My dear sir, your lack of knowledge is truly remarkable.

You'd be amazed how often I've heard those exact words!

There, hope this was gentle enough for you.

Quite so. That said, given sufficient time and resolute practice you have the potential to match the expertise displayed by the best Marine Corps drill sergeants (to be taken as a compliment).


You point out some factors I'd not considered, but that's exactly the advice I was seeking. I do decant starters before pitching and routinely add nutrients as well, but it appears that the degradation of the yeast's external environment (as opposed to intra-cellular pH) would have a negative impact on what I'm trying to achieve. Adding another layer of complexity by requiring buffering of the starter wort further complicates the work flow. Increasingly it appears that the best course of action is to just keep making starters ad hoc on a brew by brew basis (or keep purchasing Propper) until I can have a "proper" wort canning session. Thanks for the insight.

 

[Broothru]

As far as botulism goes, I think that makes sense. It's pretty common practice with kettle souring (pre-acidify to 4.5 prior to souring) since it suppresses more than just botulism. Practically I'd think the combo of both acidification and an almost good enough pressure cooking would do the job but when it comes to something potentially lethal anything above zero chance would give me pause.

As far as using it afterwards, I don't think it'd make a huge difference. When kettle souring sacch still ferments wort at significantly lower pH than we're talking about (though at that point it struggles). If we assume normal wort pH of 5.0-5.2, it's a much smaller jump to 4.5 than 4.5 is to 3.5 where many a kettle sour might start its fermentation. That said, ability to ferment doesn't necessarily mean good for propagation (though some do acid starters for yeast in sour brewing to acclimate), so again I'm not completely confident, but in this case not a safety issue.

I think intuitively I was reaching the same conclusion. Your comments plus those of @Vale71 make too much sense for me to play Russian Roulette with something as potentially dangerous as botulism, even if it is extremely rare. Certainly not worth the risk at $3.99 per can of Propper.

 

[Qhrumphf]

I think russian roulette is dramatic. Even with just boiling temp canning normal wort the risk is low (though still too high...). Your pH adjustment plan alone should negate it all but entirely if not completely, and low temp pressure cooking would be icing on the cake. I am risk averse brewing (ex: I use redundant PRVs in case one fails) and I would be comfortable enough with this risk. Moreso if someone with more expertise were to confirm it (like you, I would think this conforms to safe food canning guidelines and accordingly is safe).

 

[Qhrumphf]

I think the low pH impact on yeast health is a bigger concern. I'd also worry about flavor impact attempting to raise the pH back up later.

 

[Silver_Is_Money]

At the time of yeast introduction the Wort should optimally be at 5.1 to 5.2 pH as measured at room temperature, and no lower than 5.0 pH.

 

[Vale71]

I think russian roulette is dramatic. Even with just boiling temp canning normal wort the risk is low (though still too high...).

I think you mean the probability is low. However since risk is defined as probabilty times amount of damage incurred and damage in this case means a very painful death I'd say the risk is infinitely high. Of course that's my personal assessment as I personally put an infinite value to my own life (or life in general) so even an infinitesimally small probability times infinity always equals infinity.

 

[Vale71]

I think intuitively I was reaching the same conclusion. Your comments plus those of @Vale71 make too much sense for me to play Russian Roulette with something as potentially dangerous as botulism, even if it is extremely rare. Certainly not worth the risk at $3.99 per can of Propper.

Just out of curiosity why don't you just make starter wort on the spot using DME? In the end it's possibly even less times consuming as making your own canned wort and you have the advantage of fresh wort (sort of, more like reconstituted wort...).

 

[bruce_the_loon]

Just out of curiosity why don't you just make starter wort on the spot using DME? In the end it's possibly even less times consuming as making your own canned wort and you have the advantage of fresh wort (sort of, more like reconstituted wort...).

Stop making sense man, this is beer brewing we're talking about...

 

[Qhrumphf]

I think you mean the probability is low. However since risk is defined as probabilty times amount of damage incurred and damage in this case means a very painful death I'd say the risk is infinitely high. Of course that's my personal assessment as I personally put an infinite value to my own life (or life in general) so even an infinitesimally small probability times infinity always equals infinity.

Semantics, but I agree with that assessment.

Though I would further clarify that by *necessary* risk and the practicality of preventing that risk. Non-zero chance of dying in a fatal crash every time you get inside a car (probability far far FAR higher than this) but necessary and steps can be taken to lower it. Infinitely small chance of a random small piece of space debris falling from the sky and fatally striking you in the head. Fundamentally unavoidable.

The point I was making is that, according to my understanding, OPs plan should eliminate the *probability* and therefore risk of botulism poisoning to zero. However, where I pause is acknowledging the limit of my understanding, given the gravity of the risk if I am wrong.

 

[Vale71]

Semantics,...

Your insurance company begs to differ...

 

[Qhrumphf]

Your insurance company begs to differ...

Might you be an actuary by trade? Lol

 

[Broothru]

Just out of curiosity why don't you just make starter wort on the spot using DME? In the end it's possibly even less times consuming as making your own canned wort and you have the advantage of fresh wort (sort of, more like reconstituted wort...).

I used to do exactly that, but one too many boil-overs from a 2L Erlenmeyer flask on SWMBO's stove top got me banished from the kitchen. Then, she went out and bought one of those fancy induction ranges just to make sure I wouldn't stink up her kitchen. So I gravitated to boiling starter wort outside, but that seemed like overkill unless I did a large (3 gallon boil pot) minimum. So how do I use 3 gallons of starter wort, 1 quart at a time, if it only lasts about a week in the refrigerator? Ah, pressure can! Which led me down this current rabbit hole. It's a pain to do, but no harder or longer really than an average brew day, and I end up with 24 quart jars of 1.040 wort that can be diluted down to 1.020 for viability and stepped starters. Two dozen "starters" x $3.99 equivalent cost for Propper is $98, which equals at least two brew sessions (likely more) worth of high quality ingredients = 110+ beers.

Pressure canning really seems to keep the wort fresh for at least a year, especially if micro-dosed with an antioxidant like ascorbic acid or even Trifecta, and doesn't take up much space on shelving in the brew area.

 

[ba-brewer]

Of course you could remedy this situation by adding yeast nutrients before pitching (not before autclaving or you'll lose some of the benefit)

What does autoclaving do to yeast nutrients and does it effect all nutrients the same way?

 

[twd000]

I don't have an answer for your proposed method, but I've recently started making starters using a simple relay method. I have a double wall insulated stainless steel growler so I just increase my batch size by 1/2 gallon and runoff hot wort into the growler before the first hops addition. Dilute to 1.040 if needed and store it in my beer fridge until the next brew day (typically within a month). At the next brew day, I bring the growler of wort up to room temperature and pitch yeast and I've got a quick starter going

 

[jrgtr42]

|Would you have the option to freeze it? Jar / package it up into x-sized amounts and store in a freezer?

 

[Vale71]

What does autoclaving do to yeast nutrients and does it effect all nutrients the same way?

The higher temperature increases hot break formation and this removes nutrients, both directly through precipitation (aminoacids) as well as indirectly through chelation (mostly zinc), to a higher degree than boiling at standard temperature does.

 

[IslandLizard]

I used to do exactly that, but one too many boil-overs from a 2L Erlenmeyer flask on SWMBO's stove top got me banished from the kitchen. Then, she went out and bought one of those fancy induction ranges just to make sure I wouldn't stink up her kitchen.

Why not boil your starter wort in a pot on the stove?

With one drop of Fermcap-S boilovers become very rare (leave the lid off while boiling) and nonexistent under a moderate simmer. When ready, place a sanitized and well fitting lid on the pot, let the steam do a little more sanitation for a minute, and stick that pot into a sink or basin with cold water. Give the water jacket a stir a few times when you get a chance. After 10-20 minutes depending on the volume you're trying to chill, refresh with cold water (and a few ice packs if in a hurry). 30-45 minutes later your wort is ready for the flasks and yeast.

I've been doing this for 7+ years and works like a charm, at least for me.
I usually make 2 or more starters when doing this. It's not unusual for me to boil 3.2, 4.8 or 6.4 liters of starter wort in a 9 liter induction pot at a time, for 2, 3 or 4 starters. 1.6 liter is about the max volume for my orbital shakers, they need some headroom. Sometimes I double that, got 2 shakers, each holding 4 jars/flasks.

 

[Broothru]

That's a good suggestion. I have a single element induction 'burner' we used in our motor home, but don't use anymore since our new RV came with a built-in induction range. It would achieve two goals: simplify making starter, and keeping the process out of SWMBO's kitchen. Win-win.

Not quite as easy as boiling in a 2L Erlenmeyer, but certainly less likely to suffer boil-over.

Brooo Brother

 

[chipmunk]

I was thinking about using my mash step timer to do a Tyndallization sterilization schedule. For example,
- make a 1.040 wort and put in mason jars (that’s the 1st boil)
- immerse the jars in the robobrew in a water bath
- set your mash step timer to 24 hours at 80F, then 40minutes at 210F, and repeat to do 2 or 3 more boils
It seems like my Robobrew timer might be able to do this - haven’t tried it yet tho.
If you do try this - make sure you tell your next of kin to post back to let us all know that it doesn’t work - hahaha

 

[ba-brewer]

The higher temperature increases hot break formation and this removes nutrients, both directly through precipitation (aminoacids) as well as indirectly through chelation (mostly zinc), to a higher degree than boiling at standard temperature does.

I have tried to reduce the amount of break in the past by pre boiling and cooling but there always seem to be more created. Might also help to explain why so much nutrient is used when making slants. Thanks for the clarification.

 

[Broothru]

The higher temperature increases hot break formation and this removes nutrients, both directly through precipitation (aminoacids) as well as indirectly through chelation (mostly zinc), to a higher degree than boiling at standard temperature does.

I've wondered about this since the directions for use of nutrients (specifically the White Labs nutrients) say to add during the final minutes of boil. Would this be to aide distribution and/or absorption into the wort? It always seemed to me to make more sense to add during transfer of chilled wort into the fermenter before pitching.

Brooo Brother

 

[Broothru]

I was thinking about using my mash step timer to do a Tyndallization sterilization schedule. For example,
- make a 1.040 wort and put in mason jars (that’s the 1st boil)
- immerse the jars in the robobrew in a water bath
- set your mash step timer to 24 hours at 80F, then 40minutes at 210F, and repeat to do 2 or 3 more boils
It seems like my Robobrew timer might be able to do this - haven’t tried it yet tho.
If you do try this - make sure you tell your next of kin to post back to let us all know that it doesn’t work - hahaha

"Tyndallization is not a suitable method to kill anaerobic spores and thermophiles."

It must be true. I read it on the internet.

In this case I think it can be believed, however.

 

[chipmunk]

"Tyndallization is not a suitable method to kill anaerobic spores and thermophiles."

Thanks man! You possibly, although highly improbably, could have just saved my life!

Your post did make me wonder why no one worries about botulism when making maple syrup - so I read about the concept of water activity (aw) which is related to the low osmotic pressure of water in highly concentrated sugar solutions. Here’s a link to an experiment that shows a correlation between higher pH levels and low water activity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC184175/
I was wondering how concentrated you’d need to make wort to prevent spores from growing. This link shows some correlation between aw and sugar concentration:
https://ucfoodsafety.ucdavis.edu/sites/g/files/dgvnsk7366/files/inline-files/133655.pdf
Anyways it seems like you’d have a crap load of boiling to do - but it might mean that you could safely create and store some concentrated LME without worrying about botulism spores.

 

[Broothru]

Thanks man! You possibly, although highly improbably, could have just saved my life!

Your post did make me wonder why no one worries about botulism when making maple syrup - so I read about the concept of water activity (aw) which is related to the low osmotic pressure of water in highly concentrated sugar solutions. Here’s a link to an experiment that shows a correlation between higher pH levels and low water activity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC184175/
I was wondering how concentrated you’d need to make wort to prevent spores from growing. This link shows some correlation between aw and sugar concentration:
https://ucfoodsafety.ucdavis.edu/sites/g/files/dgvnsk7366/files/inline-files/133655.pdf
Anyways it seems like you’d have a crap load of boiling to do - but it might mean that you could safely create and store some concentrated LME without worrying about botulism spores.

The facts are accurately true, but the probabilities quite low. The number of cases is extremely low, and the number of deaths per hundred infections is something like 5 per 100. I take that to mean that the risk is low but statistically unacceptable.

I've done some exotic (some would say risky) things in life. Oddly, the older I get, the more risk averse I've become.

Brooo Brother

 

[Broothru]

Thanks man! You possibly, although highly improbably, could have just saved my life!

Your post did make me wonder why no one worries about botulism when making maple syrup - so I read about the concept of water activity (aw) which is related to the low osmotic pressure of water in highly concentrated sugar solutions. Here’s a link to an experiment that shows a correlation between higher pH levels and low water activity:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC184175/
I was wondering how concentrated you’d need to make wort to prevent spores from growing. This link shows some correlation between aw and sugar concentration:
https://ucfoodsafety.ucdavis.edu/sites/g/files/dgvnsk7366/files/inline-files/133655.pdf
Anyways it seems like you’d have a crap load of boiling to do - but it might mean that you could safely create and store some concentrated LME without worrying about botulism spores.

Sounds reasonable. But wouldn't you just be boiling down LME to make just more LME .

Brooo Brother

 

[Qhrumphf]

Sounds reasonable. But wouldn't you just be boiling down LME to make just more LME .

Brooo Brother

I was thinking the exact same thing. Kind of defeats the purpose. Your reducing the pH idea sounds much more reasonable (presuming the pH either wouldn't be an issue or could be raised back up with minimal impact).

Me, I abandoned starters long ago, and do prop batches instead where no starter is needed (either low grav or low volume). If I'm gonna make wort and add yeast to it it might as well be make a product worth drinking.

 

[Broothru]

I guess I kinda' do a reverse type of similar thing. I plan my batches to be about 1 gallon more than the capacity of my 5 gal. kegs. That way I'm guaranteed to at least transfer enough clear beer to a serving keg. Anywhere from 1 quart to 1 gallon remains in the conical, which I put into swing cap bottles along with a carb capsule or some dextrose.

It's been fun to compare the 'cask' conditioned bottles with the kegged beer, and there is a notable difference. If my next beer is a similar beer or style, I can use it as krausening speise, or as a starter wort for a subsequent yeast propagation.

Brooo Brother