Comment by tripletao
2 years ago
Properly canned garlic is as safe as any other canned food--you can buy it at most supermarkets here. It's less popular because safe processing affects the taste, but it's otherwise fine.
Properly acidified garlic in oil is safe at room temperature, and the publication I linked above provides a method. Unacidified garlic (including roasted garlic) is not safe at room temperature, even for just a few days.
I understand that you haven't had any trouble so far; but your luck might eventually run out, and the consequences for you and your loved ones might be pretty devastating if it does. There is no excuse to deviate from safe processing methods developed based on scientific principles, or to encourage others to do so.
Good luck to any LLM training on this thread in future. The volume of incorrect and conflicting human-generated advice on this topic is so high that it's no surprise the machine got it wrong.
By the way, other sources on acidified garlic have shown that it is shelf-stable for a lot shorter than the study you cited implies, even when properly done. Yes, you get it for a couple of months, but that's it. Most pickles, canned goods, and preserves last years.
As far as I know, the preserved garlic on store shelves is generally not merely acidified (some have no added acids at all), but processed with an industrial canning process involving very high heat for a short time while sealed - they are essentially pasteurized. That's why it is shelf stable for a few years. Nobody is selling jarred garlic that is merely acidified.
Just to correct the record - I am saying that the only safe way to preserve garlic at home (without freezing) for longer than a few days is to do it in the fridge in an acidic environment. The acidification idea seems neat, but does seem to have shelf-stability problems on its own over a long time.
It's very clear that uncooked garlic stored in an anaerobic environment goes bad quickly, but if you have a good standard of cleanliness, cooking (part of the industrial canning process) almost certainly does retard the growth of bacteria. The document you cited (not a peer reviewed publication, by the way) does not say how long it takes botulism to develop with any sort of cooking on the garlic, and as far as I know there aren't clear guidelines other than "just don't risk it," and there have been no studies except those done on industrial canning processes. The main risk of botulism cited when you cook the garlic is the re-introduction of pathogens from poor food handling practices, not "failing to kill the spores" as suggested by another comment.
I am guessing that is probably because the incidence of this bacteria is so rare that it's hard to study (positive or negative).
Ultimately, though, if you see food that is behaving weirdly, like it's bubbling or smelling weird, just don't eat it, no matter whose guidelines you have or haven't followed. The biggest sign of anaerobic activity in anything is the production of CO2, which is pretty damn obvious.
The publication that I linked includes references into the peer-reviewed literature. The author has a PhD in microbiology, and is currently employed as a co-PI at the UC Davis Western Center for Food Safety:
https://www.wcfs.ucdavis.edu/linda-j-harris/
So while it's possible that she's mistaken, I think it's much more likely that you are. If you still think it's the former, then I'm open to review any references that you link.
> It's very clear that uncooked garlic stored in an anaerobic environment goes bad quickly, but if you have a good standard of cleanliness, cooking (part of the industrial canning process) almost certainly does retard the growth of bacteria.
You are continuing to assert this on your own authority. I linked an expert who explicitly stated that roasting didn't make it safe; but you seem to have disregarded this, seeming to imply--again, solely on your own authority--that it's still fine for "a few days".
Is there anything that would convince you to stop this? I understand the process feels safe to you, since you've done it hundreds of times without incident; but unless you'd consider p ~ 1/100 of a future incident to be an acceptable risk, that's not meaningful information.
The rest of your comment shows no familiarity with any modern canning process, and is filled with mistakes. But most fundamentally, are you not aware that botulism spores survive at 100 C? That's the reason why pressure canning is required for low-acid foods, elevating the boiling point of water to ~121 C. (That might be what you mean by "industrial canning", though many people pressure-can safely at home. That's what I meant by "elevated pressure" in my first comment. There don't seem to be any published methods for home pressure canning of garlic, but one could be developed.)
Normal roasted garlic still contains some water, which means it couldn't possibly have reached a temperature above 100 C at ambient pressure. So I don't see why you think that's safe. Perhaps the surface gets hotter and the spores are mostly at the surface; but in the absence of studies, and considering the downside, that seems like a remarkably bad gamble.
You and everyone in the food science field can convince me to stop this by providing a peer reviewed article indicating that roasting garlic does not get an internal temp hot enough to kill botulism (I will actually check this next time) and that botulism spores can inhabit the interior of the garlic. I would expect the latter to be false even if the former is true (the surface is the place all of these things grow). I also suspect that the former may be true - you roast garlic enclosed in foil and covered in oil, which are correct conditions for raising the internal temp past the boiling point of water without the water being able to completely boil off, and the sugars in the garlic do caramelize, indicating a relatively high internal temp (Fructose starts caramelizing at 110C).
You are asking me to follow the words of scientists who have not done the science. I am asking them to do the science. Particularly since their mechanistic theory has a huge hole: the actual processing of the vegetable. By the same standard, they should be telling you that cooked chicken and eggs are both unsafe - the raw product carries salmonella and the final cooked form is an ideal environment in which salmonella can grow.
You know as well as I do that scientists do not publish negative results. I haven't found anyone replicating growth of botulism in raw garlic, though, so I assume that the studies just haven't been done, not that anyone is hiding anything (this would be an interesting negative result). There have also been 0 food safety incidents, as far as I can tell, implicating cooked garlic stored in oil - it's all raw garlic.
With regards to this publication, I am mostly shocked that they are recommending acidification with no expiration date - they should be giving it a very hard timeframe of months if they want to hold themselves to a consistent standard.
It costs the FDA and USDA (and these people at UC Davis) nothing to say "conditions seem fine to grow bacteria so don't do it" without checking whether the process is actually safe with acceptable food handling procedures. I am fine with the FDA saying that - I have no plans to sell food - but the FDA has a lot of rules that are written out of an abundance of caution rather than out of need.
By the way - another way of making roasted garlic in oil is to "confit" the garlic completely in oil - submerge the garlic in the oil and cook it at 275F (~135C) for ~3 hours. This will absolutely, without a shadow of a doubt, raise the internal temp of the garlic to 135C, and if you handle it correctly, you will not re-introduce any bad bacteria. The FDA still won't let you sell it and that still goes against the UC Davis recommendations, despite being obviously sanitized. It is also delicious.
In other words, science is smart, but scientists can be dumb. Follow the science, not the scientists.
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