Wort pH and Risk of Botulism

[Brooothru]

So the take-away is to pressure can my starter worts to eliminate botulism spores as well as opportunistic bacteria and wild yeast. There is no shortcut to science that provides an equivalent measure of safety. Though the overall risk seems low, it doesn't warrant the statistical chance of things going south. 250F + for :20 minutes it is!

Brooo Brother

 

[Birrofilo]

I think microwave ovens are the most overlooked device we homebrewers have at home.
4 minutes in a microwave at 900W are guaranteed to kill anything that was attempting to gain a living in your wort, and also to degrade the botulinus toxines, besides killing the spores.

A Microwave oven is also very good to sanitize (or actually sterilize, if you so wish) metal objects such as metallic taps (I have two metallic fermenters with metallic taps) during your pre-brewing routine. Just immerse the tap in a microwave-oven-suitable bowl letting it completely immersed in water, and put the bowl in the microwave oven, and let it go (watch the process: the water might boil and overflow, then stop, use a larger container and a larger quantity of water, repeat).

1 minute will sanitize adequately, 4 minutes will kill any form of life discovered by science since the times of Saint Louis Pasteur.

I never tried with borosilicate glass, but I do presume one can succesfully sanitize borosilicate-glass objects. Best is to immerse the object in water so that it is also surrounded by boiling water, lest "Hot spots" in the oven heat the object irregularly and stress the borosilicate glass.

Life uses water. Bacteria and such creatures are made of a membrane which contains water-rich living matter.

When you use a microwave oven, the microwaves cause the water inside the creature to boil, that creates gas bubbles which literally burst the microbe, that works also at a microscopic level. In a microwave, microbes have no place where to hide. They will die, I tell you.

For what I know, microwave ovens are increasingly used in chemical laboratories for sterilization purposes. It's good stuff.

PS Do not put in the microwave oven any hermetically closed container because it will explode.

 

[madscientist451]

Sorry, I don't get it, why go though a big hassle to make a canned wort for a starter? I take a quart of water, heat it to just below boiling, toss in some DME, put the lid on the pot and in the morning I dump it into a 1/2 gallon jug and toss in the yeast. Why would I want to go through all the extra work to make canned starter wort that might cause some problems?

 

[Birrofilo]

I don't get it myself as well, but the OP gave an answer in post #39, which can be summarized in "it's not the destination, it's the road" stuff.

 

[madscientist451]

Oh ok, now I get it, let's do things the "hard way".

 

[bu_gee]

Sorry to show up late to the party, but it was my understanding that the botulism toxin is easily denatured. A quick perusal of the Googletron seems to indicate 85°C for 5 minutes is sufficient.

So with that in mind, I would like to propose an alternative: Pressure can your wort with your Fagor and make yourself a war chest. Between the day before you need it and 2 hours before you need it, pop it either back in the pressure canner (I like the Instant Pot for this) or a water bath to denature any potential toxin, chill in an ice bath, and pop it in the refrigerator. The cold will keep the C. botulini from getting too frisky before you use it the next day.

 

[marc1]

I think microwave ovens are the most overlooked device we homebrewers have at home.
4 minutes in a microwave at 900W are guaranteed to kill anything that was attempting to gain a living in your wort, and also to degrade the botulinus toxines, besides killing the spores.

A Microwave oven is also very good to sanitize (or actually sterilize, if you so wish) metal objects such as metallic taps (I have two metallic fermenters with metallic taps) during your pre-brewing routine. Just immerse the tap in a microwave-oven-suitable bowl letting it completely immersed in water, and put the bowl in the microwave oven, and let it go (watch the process: the water might boil and overflow, then stop, use a larger container and a larger quantity of water, repeat).

1 minute will sanitize adequately, 4 minutes will kill any form of life discovered by science since the times of Saint Louis Pasteur.

I never tried with borosilicate glass, but I do presume one can succesfully sanitize borosilicate-glass objects. Best is to immerse the object in water so that it is also surrounded by boiling water, lest "Hot spots" in the oven heat the object irregularly and stress the borosilicate glass.

Life uses water. Bacteria and such creatures are made of a membrane which contains water-rich living matter.

When you use a microwave oven, the microwaves cause the water inside the creature to boil, that creates gas bubbles which literally burst the microbe, that works also at a microscopic level. In a microwave, microbes have no place where to hide. They will die, I tell you.

For what I know, microwave ovens are increasingly used in chemical laboratories for sterilization purposes. It's good stuff.

PS Do not put in the microwave oven any hermetically closed container because it will explode.

I agree microwaves can be used for sterilization (some searching shows it can be done commercially for food products), but what sources do you have for protocols for home microwave ovens? This is interesting.

Thanks!

 

[marc1]

Sorry to show up late to the party, but it was my understanding that the botulism toxin is easily denatured. A quick perusal of the Googletron seems to indicate 85°C for 5 minutes is sufficient.

So with that in mind, I would like to propose an alternative: Pressure can your wort with your Fagor and make yourself a war chest. Between the day before you need it and 2 hours before you need it, pop it either back in the pressure canner (I like the Instant Pot for this) or a water bath to denature any potential toxin, chill in an ice bath, and pop it in the refrigerator. The cold will keep the C. botulini from getting too frisky before you use it the next day.

This defeats the purpose of having starter wort ready-to-use.

Planning on having jars sitting around that may have deadly poison in them seems like a bad practice.

 

[Vale71]

Planning on having jars sitting around that may have deadly poison in them seems like a bad practice.

Totally agree. This would be just about as safe as having strong caustic or acid solutions stored in a mineral water bottle with a hand-written label that says "poison" pasted on. People have lost the use of their stomach or died because of stupid stuff like that.

 

[Birrofilo]

@bu_gee

For what I remember, Botulinus toxins are degraded with heat, but Botulinus spores are much more resistant to heat than their toxins. If the bacterium is in his "normal" form it can be killed with a normal thermal procedure, but if it is in his "spore" form it needs an "extreme" thermal process to get rid of, because the protein shield will isolate the bacterium from external aggressions and will prolong his time to death when heated. Microwaves will kill it "from the inside" and no protein shield will shield it. Normally you want to get rid not only of spores (which is what actually kills you) but also of the bacterium itself. Survival of the spore is not a problem for beer (boiling for 60' in an acid environment would kill the spore ten times, so to speak) but for other food preparations it is.

@marc1

In my internet wandering in search of information to make life (and brewer's life) easier I do come across sources which I deem reliable, and I take note of the information which is useful for my life. I don't usually take notes about the sources themselves because, you know, I'm not writing a "paper" ;-)

Yet, I do remember having read of chemical laboratories using microwaves for sterilization purposes, from sources which I deemed reputable. Chemical laboratories have a large need for sterilization means and for what I remember microwave ovens are making some sort of "small revolution" in the field, a bit like "all in one" kettles are doing in our field ;-)

People is often put off by the notorious incompatibility between microwaves ovens and iron or steel items. But that is a misconception. If you immerse in water the metal or the object, there will be no problem at all.

The usefulness of this procedure is very high not only for metal objects and for borosilicate glass, but also for small silicon hoses. E.g. you can sterilize your aeration stone with all the silicon hose attached to it. That's not just practical, but you can also avoid touching the stone to fit the silicon hose again after having sterilized the stone alone. Just put everything in a bowel filled with water and that's it, your stone is ready for use and perfectly sterilized, and you use no sanitizing agent risking to obstruct its pores.

 

[bu_gee]

@bu_gee

For what I remember, Botulinus toxins are degraded with heat, but Botulinus spores are much more resistant to heat than their toxins. If the bacterium is in his "normal" form it can be killed with a normal thermal procedure, but if it is in his "spore" form it needs an "extreme" thermal process to get rid of, because the protein shield will isolate the bacterium from external aggressions and will prolong his time to death when heated. Microwaves will kill it "from the inside" and no protein shield will shield it. Normally you want to get rid not only of spores (which is what actually kills you) but also of the bacterium itself. Survival of the spore is not a problem for beer (boiling for 60' in an acid environment would kill the spore ten times, so to speak) but for other food preparations it is.

I should stress that I'm not a microbiologist here, but from what I remember about it, the botulism toxin is only created when the bacteria goes into its spore form. Getting rid of the bacteria or the spore isn't entirely necessary as once it is in our digestive systems, it no longer poses a risk to us. It is really the toxin itself that causes the problem. If spores actually caused us problems we wouldn't be able to eat any agricultural products, particularly honey, because the spores are all over them.

I had merely posed it as an intermediate solution. Not perfect, but far closer to a ready to use product than a bag of DME.

As for microwave sterilization, and this may have been said before, I would be nervous without an adequate laboratory to determine if the process did actually work. Commercial canning companies with all the equipment will all the bells and whistles still check all of their products susceptible to C. botulini just to be sure because that process isn't exactly 100% either.

 

[Birrofilo]

@bu_gee

If the bacterium remains alive, through your knives, forks etc. it can infect some other food. There it can turn into the spore form and create the toxin which might kill you.
You normally want to kill the problem at the source, you want to minimize the Botulinum which is hanging around.
To state it in another way, it's not the terrorist which kills you, it's the explosive, but in order to avoid terrorist explosions you have to chase terrorists, not only explosives ;-)

 

[bu_gee]

@bu_gee

If the bacterium remains alive, through your knives, forks etc. it can infect some other food. There it can turn into the spore form and create the toxin which might kill you.
You normally want to kill the problem at the source, you want to minimize the Botulinum which is hanging around.
To state it in another way, it's not the terrorist which kills you, it's the explosive, but in order to avoid terrorist explosions you have to chase terrorists, not only explosives ;-)

To extend your metaphor: You don't need to kill the terrorist. Forcing him into hiding is sufficient.

What does it take to force him into hiding? Oxygen is sufficient as the Clostridium genus are all obligate anaerobes. Acid (in your gut) and ethanol (in your beer) helps too.

 

[twd000]

the microwave sterilization is interesting. Have you found a time-and-temperature table for various materials and container sizes? If I had a quart jar of wort, how long would I need to microwave on high to sterilize it all the way through?

 

[Birrofilo]

To extend your metaphor: You don't need to kill the terrorist. Forcing him into hiding is sufficient.

What does it take to force him into hiding? Oxygen is sufficient as the clostridium genus are all obligate anaerobes. Acid (in your gut) and ethanol (in your beer) helps too.

Although we have a different take on terrorism ;-) that's very interesting.
I suppose you mean that Botulinum can be eliminated through means such as oxygenated water, or pure oxygen from cylinders, if the substrate is liquid.

This leads me to another question which risks derailing the thread astray: I promise the OP I will open a new thread if the answer is not fast and definitive.
The OT question is: does oxygenation with pure oxygen "sanitize" the wort or not?
If yes, there is a huge advantage in using an O2 cylinder rather than a fish tank pump.

 

[bu_gee]

Although we have a different take on terrorism ;-) that's very interesting.
I suppose you mean that Botulinum can be eliminated through means such as oxygenated water, or pure oxygen from cylinders, if the substrate is liquid.

This leads me to another question which risks derailing the thread astray: I promise the OP I will open a new thread if the answer is not fast and definitive.
The OT question is: does oxygenation with pure oxygen "sanitize" the wort or not?
If yes, there is a huge advantage in using an O2 cylinder rather than a fish tank pump.

Oxygen is tricky as it oxidizes everything it comes into contact with and in a trapped environment, such as a sealed jar, you will eventually consume it all in regular chemical reactions and eventually leave a hospitable environment for C. botulini.

You will need a constant, if small, supply of oxygen to keep the bacteria safely in their spore form. The atmosphere does a good job of that so we don't usually have to worry about botulism poisoning from knifes and forks and the sort. We're just victims of our own ingenuity that we're creating a hospitable environment in a sealed jar.

While oxygen will force the bacteria back into spore form, I don't believe that oxygen will oxidize toxin that is generated, at least not at a reasonable rate. So if you have an environment where you may have had active C. botulini, you probably want to use heat since it both forces the bacteria to form spores and destroys the toxin.

 

[bu_gee]

the microwave sterilization is interesting. Have you found a time-and-temperature table for various materials and container sizes? If I had a quart jar of wort, how long would I need to microwave on high to sterilize it all the way through?

I'm willing to bet that this unicorn doesn't exist, at least not in generic form. Heck, more and more foods are shying away from microwave instructions just because of the number of variables involved in microwave ovens.

Saying that something that works in my microwave oven will work in yours is a stretch at best, and deadly at worst.

 

[Vale71]

Survival of the spore is not a problem for beer (boiling for 60' in an acid environment would kill the spore ten times, so to speak) but for other food preparations it is.

This information is incorrect and very dangerous so please stop propagating it. Boiling at standard temperature and pressure no matter for how long will not kill C.botulinum spores and wort is not acidic enough to prevent the spores from becoming active and starting an infection which can then create the toxin itself. This is one of the reasons why storing wort after a simple boil is dangerous and that's what this thread is all about.
In brewing practice this is not a problem as you'd pitch yeast right away and this will quickly cause the PH to drop to a level that makes C.botulinum spores no longer viable, so even if they're still there there is no danger of beer becoming infected. When you are storing wort and not beer this does not apply and a different sterilization process need to be followed for the stored wort to be both shelf stable as well as safe for later human consumption.

 

[z-bob]

There's one other thing you can do that everyone seems to have overlooked. You can autoclave your acid but not acid enough wort at almost but not high enough temperature. It will be unlikely to spoil but you can't trust it. When you're ready to use it, you will have to boil it first to denature any botulinum toxin that might possibly be there. (it's extremely unlikely, but you don't want chance it) Boiling destroys the toxin and kills the bacteria.

I don't remember how long you have to boil it; 10 minutes comes to mind but I don't think it's really that long. You'll have to look that up. It should be easy to find now that you know to look for it HTH

Obviously, if the seal has failed and the wort is cloudy and smells like vomit you'll just pitch it. The danger is if the clostridium has just started to grow before you open the jar and it's not obvious yet.

 

[bu_gee]

This thread here is why we probably shouldn't have botulism conversations on this forum.

Too much misinformation and underrepresentation of the risk makes for a dangerous mix.

Working with yeast gives us all the illusion of being part-time microbiologists, but, fundamentally, 99% of us don't have the equipment to adequately control for something as dangerous as C. botulini and as a result we should treat it with extreme caution.

So, as a PSA, do research using reputable sources to understand what you can and can't do in this respect.

I have done much research and I understand more about botulism than your average idiot, but that just makes me an above average idiot. I just know enough about it for it to scare the crap out of me and to know that I'm not going to actually get rid of it.

 

[twd000]

instead of trying to make it shelf-stable, why not store the wort in the fridge until brew day? Botulinum won't grow below 40F

 

[z-bob]

instead of trying to make it shelf-stable, why not store the wort in the fridge until brew day? Botulinum won't grow below 40F

37, I believe. But your fridge should be colder than that anyway

 

[bu_gee]

instead of trying to make it shelf-stable, why not store the wort in the fridge until brew day? Botulinum won't grow below 40F

Rate x Time => A slow rate for a long time poses similar risk as a fast rate for a short time.

 

[z-bob]

Sorry, I don't get it, why go though a big hassle to make a canned wort for a starter? I take a quart of water, heat it to just below boiling, toss in some DME, put the lid on the pot and in the morning I dump it into a 1/2 gallon jug and toss in the yeast. Why would I want to go through all the extra work to make canned starter wort that might cause some problems?

In my case, it's because I have 200# of malt in my basement and only about a half a pound of DME left. So I want to figure out a process to use what I have already. And to enjoy the ride

 

[Vale71]

But your fridge should be colder than that anyway

Anybody willing to bet their life on it?

 

[z-bob]

Anybody willing to bet their life on it?

You do all the time.

 

[bu_gee]

You do all the time.

With botulism? *citation needed

 

[bu_gee]

Our usual defense against botulism is oxygen, not cold.

 

[z-bob]

Our usual defense against botulism is oxygen, not cold.

It's both. Jar of chicken stock in the fridge with a layer of fat on top, waiting to be made into soup? Maybe just I do that. OTOH, it will get boiled before it's eaten. Another example is supermarket canned hams that must be kept refrigerated.

I don't want to argue with you; I generally agree with you. But there are ways to mitigate risks.

 

[bu_gee]

It's both. Jar of chicken stock in the fridge with a layer of fat on top, waiting to be made into soup? Maybe just I do that. OTOH, it will get boiled before it's eaten. Another example is supermarket canned hams that must be kept refrigerated.

I don't want to argue with you; I generally agree with you. But there are ways to mitigate risks.

A layer of fat is permeable to oxygen which by itself will stifle C. botulini which is likely already in the stock, but it offers a substantial barrier to other bacteria entering. If you vacuum seal that jar, that changes the equation which is a good reason to not seal it, but boiling it before using it should be fine and it isn't exactly betting your life on it

Every canned ham I've ever bought was "refrigerate after opening" so I can't agree or disagree with you on that respect.n

After my last post I rifled through my refrigerator trying to find anything that is completely sealed from oxygen, not commercially canned, and won't be cooked before eating and I found none, but maybe that's just my fridge. The closest thing I found was a vacuum sealed pack of pork.

 

[Vale71]

You do all the time.

No I don't, because my refrigerator, just like any other, is a very oxygen-rich environment.

 

[z-bob]

The small canned hams are shelf-stable (just like SPAM.) I saw some at Aldi last week. The big ones are sold in the refrigerated case to prevent spoilage. I assume that includes botulism, but maybe they have enough nitrites added to prevent that. (I haven't seen a refrigerated canned ham in years because I don't look for them)

I know enough to know that I know a little but probably not much I guess it's part of that Dunning-Krueger thing; the more that I learn the less that I know. Food preservation was one of my things back in the Usenet days.

 

[Vale71]

.

 

[Birrofilo]

the microwave sterilization is interesting. Have you found a time-and-temperature table for various materials and container sizes? If I had a quart jar of wort, how long would I need to microwave on high to sterilize it all the way through?

My general guidelines is that 4 minutes kills everything and their dog. Your mileage may vary. Normally we don't need sterilization but sanitization. For that, 1 minute is sufficient. This is again from my notes, but I cannot point to specific sources, so use this information at your own peril, so to speak.

 

[Birrofilo]

This information is incorrect and very dangerous so please stop propagating it. Boiling at standard temperature and pressure no matter for how long will not kill C.botulinum spores and wort is not acidic enough to prevent the spores from becoming active and starting an infection which can then create the toxin itself. This is one of the reasons why storing wort after a simple boil is dangerous and that's what this thread is all about.

I am not convinced a living being exists that can resist a "no matter how long" boiling. This seems frankly absurd to me. We can discuss whether 60, or 100, or 150 minutes are sufficient, but "boiling forever" will certainly kill any spore or anything that lives IMHO.

For what I know, it's the combination of acidity and heat which prevents the danger. There is no clear-cut acidity or clear-cut heat. The more the acidity, the less the heat necessary. Less acid, more time needed. But I do believe there is a point where the spore dies, even if with no acidity at all.
This source says that 100 minutes should kill the spore, although it also says that some sources say what you say (many hours) but for that, again, I would like to see some experimental verification.

https://ucanr.edu/sites/MFPOC/Emergency/Botulism/
Regarding "storing wort after a simple boil is dangerous" I think the general belief is that you cannot store wort and then use it "as is", you have to boil it first to use it. I agree using stored wort without boiling is dangerous. I don't agree using stored wort after prolonged boiling is dangerous, if that's what you mean.

" Despite its extreme potency, botulinum toxin is easily destroyed. Heating to an internal temperature of 85°C for at least 5 minutes will decontaminate affected food or drink. "

What ultimately kills human beings is the toxin. Getting rid of the spore is useful and important if the food is going to be used again. If one drinks all the boiled wort (without using it for repitching, for instance) then destroying the toxin is enough because the spore is dangerous to the extent that it produces the toxin. On the other hand, using questionable wort to prime beer for bottling would certainly be dangerous.

As a side note, everybody in Italy used to make canned homemade tomato sauce. That has a pH of 4,6 if memory serves, but that doesn't mean that the botulinum has an easy life if boiled at pH pH 4,7, pH 5 or pH 5.4. Acidity is a factor in killing the botulinum, and the more, the better.

pH 4.6 is not a "threshold" or a "red line", because nobody would prepare canned sauce without a large safety margin. Millions of people grew up with that stuff prepared at home with all possible human mistakes and procedure imperfections.

The Ancient Romans used to eat ham and salami and that stuff is not cooked, it's consumed 6 months after preparation or later, and they did not have modern preservatives nor they had the way to inoculate the meat with lactic bacteria. Although notoriously that meat was not perfectly safe, it certainly was not deadly and was mostly safe. Salami reaches pH 5,3 or so.

I remain convinced that the acidity of wort is effective in killing the spore with sufficient heat, but remain open to any documented fact in the other direction, of course.

 

[z-bob]

You don't need to kill the spores (although it's good if you can accomplish that), you just need to keep them from sprouting. Low water availability will do that -- that's why honey doesn't spoil -- and I think that's what low pH does also.

 

[Vale71]

This source says that 100 minutes should kill the spore, although it also says that some sources say what you say (many hours) but for that, again, I would like to see some experimental verification.
https://ucanr.edu/sites/MFPOC/Emergency/Botulism/

No, it most definitely doesn't. Please stop spreading incorrect and dangerous information. From your own source:

"

5. How long does it take at rolling boil 212 F to kill Botulism spores? How many hours? There are people without access to anything except wood fires.


I do not believe this is known. As stated above even at high pressure the appropriate processing times range from 20 to 100 min depending on the food. At a rolling boil one would expect similar large variability and orders of magnitude longer times. At this point one would question the palatability of the food in question – possibly why we do not have this information. Sometimes one sees general statements that C. botulinum spores will survive 5 to 10 hours of boiling but this is meant as an example of how heat resistant the spores are and should not be interpreted as validated processing times.

"

 

[Vale71]

The Ancient Romans used to eat ham and salami and that stuff is not cooked...

It's also not preserved in a strictly anaerobic packaging, quite the opposite actually. The comparison is completely meaningless in the context of botulinum.

 

[Birrofilo]

I'm willing to bet that this unicorn doesn't exist, at least not in generic form. Heck, more and more foods are shying away from microwave instructions just because of the number of variables involved in microwave ovens.

Saying that something that works in my microwave oven will work in yours is a stretch at best, and deadly at worst.

I found this reputable source regarding sterilization with a microwave

https://www.cdc.gov/infectioncontrol/guidelines/disinfection/sterilization/other-methods.html
As you see, the maximum which is considered is 5 minutes for a home-type microwave oven. Other sources indicate 1 minute sterilizes all but the most "robust" microbes.

For what is of interest to homebrewers, whose goal is normally sanitization rather than sterilization, microwave ovens are absolutely useful.

I won't bet about unicorns, though

PS This source indicates heat as the real sterilizing agent, and maybe radiation itself. For what I have read though (where? I don't know) it's really the explosion of the microbe from inside which is deadly. That should certainly include the spores of botulinum, if that mechanism is actually in place. Regardless, microwave ovens as a means of sterilization is a reality.

 

[Birrofilo]

After my last post I rifled through my refrigerator trying to find anything that is completely sealed from oxygen, not commercially canned, and won't be cooked before eating and I found none, but maybe that's just my fridge. The closest thing I found was a vacuum sealed pack of pork.

Many homebrewers use dried yeast from opened and re-sealed packs which is completely sealed from oxygen, self-sealed from oxygen (with one of those home machines to make vacuum) therefore not commercially canned, and won't be cooked before eating.

Your home-made beer is probably completely sealed from oxygen, won't be cooked before eating, it's not commercially canned, and it's safe to be consumed, even though it has a pH of 5 or so.

Also, it is common practice to vacum-seal cheese and consume it much after the vacuum procedure and it won't be cooked before eating.

A similar procedure is applied for home-dried food, such as bananas, tomatoes, aubergines, onions etc.

Regarding fresh food, that's also often kept in a vacuum or almost-vacuum condition (with those manual pumps) and then consumed without re-cooking it (peppers, chicory, whatever). Overall, vacuum is a valid preservative even when it's not industrially made.

For what I know, the danger of botulinum doesn't normally exist because the food hosts a host of different bacteria, not just botulinum.

What makes botulinum dangerous, in home canning, is that all other bacteria are killed, and the botulinum remains alone sitting at the table, thus creating the conditions for a huge proliferation of it. The only way in which botulinum kills is through an imperfect sterilization procedure.

If the substrate is "crowded" by other microbes, the botulinum will not have the space to expand.

Basically, a food (a substrate) is like the tube during peak hours: you cannot reproduce more than much, because you have no space, other bacteria are "crowding" the substrate and are literally occupying the place.

This is also the reason why sauercrauts, salami, ham, etc. can be safe to consume, and sauercrauts remain safe to consume row, even after many months in the fridge, because molds have a hard time trying to find a place at the table.

C. botulinum is not really "competitive" when other microbes are present. It needs an empty environment to thrive. This empty environment is, in its ideal form, an imperfectly sterilized and sealed can. There is no mortal risk of botulinum in food which did not undergo a failed attempt at sterilization. (there is a non-mortal risk with row fermented food if the substrate was not adequately prepared, that's another thread).

Our defense against botulinum is not oxygen, is all other bacteria and molds and yeasts etc. which contaminate the food much faster and much better than botulinum.

I make sauercrauts at home, I experienced 1-year old sauercrauts of chili-peppers kept in the fridge. At 9 months they were still very good, at 12 months they begun having a hint of cheese.

Your bottle of Tabasco sauce will remain good for many, many months after opening, without spoling, for the same reason I suppose (that's fermented food, if memory serves).

As a side note, industrial beers are not sterilized (only pasteurized) and many "craft beers" are not even pasteurized, yet they pose no risk of botulinum, even though their acidity is less than what appears to be considered safe by some.

With all that said, I definitely would boil old wort, and not just for botulinum, but for all the other microbes which can thrive in there!