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Safe use of home-"canned" vegetables?


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11 replies to this topic

#1 pep.

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Posted 04 November 2012 - 12:13 PM

Last year, my mother "canned" some tomatoes and some mixed vegetables (think ratatouille) by bringing them to a rolling boil and filling them into clean twist-off jars while hot.

Can any of these preserves be made safe to consume (if they have not obviously spoiled), e.g. by re-boiling them for X minutes, or does she have to throw them out?

#2 Lisa Shock

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Posted 04 November 2012 - 12:37 PM

Re-boiling won't get rid of toxins that have been created by bacteria, like, say, botulism. These toxins can be colorless, odorless, and fatal in very small amounts.

There are several categories of foodborne illness. You've got pathogens which infect the body and make you ill, like e. coli, parasites, like worm eggs in fish, and, toxins created by bacteria and other organisms.

I'd toss them all.

It's not just the foodstuffs and how they were handled, I'd also be suspicious about the 'clean' jars. Canning requires sterilized jars. Based on just the handling of the jars, I'd toss the lot.

#3 pep.

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Posted 04 November 2012 - 12:54 PM

Re-boiling won't get rid of toxins that have been created by bacteria, like, say, botulism. These toxins can be colorless, odorless, and fatal in very small amounts.


Actually, as far as I know botulinum toxin is heat-labile. The spores are heat-resistant. That's why I'm asking. I'd have to test one of the jars, but I would assume that the tomatoes are relatively acidic, which should hamper the growth of clostridium botulinum (but probably not acidic enough to be safe unheated).

There are several categories of foodborne illness. You've got pathogens which infect the body and make you ill, like e. coli, parasites, like worm eggs in fish, and, toxins created by bacteria and other organisms.


Yes, I know that of course. I should have been more specific with my question. In this situation, I'm mostly concerned with bacterially produced toxins. Everything else should be pretty dead.


It's not just the foodstuffs and how they were handled, I'd also be suspicious about the 'clean' jars. Canning requires sterilized jars. Based on just the handling of the jars, I'd toss the lot.


I wrote "clean" because I was not there to inspect her procedure. However, she has made jams and various vinegar-pickled things all her life, so I'm not overly concerned with that aspect.

#4 radtek

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Posted 04 November 2012 - 01:15 PM

Boiling takes care of everything except Clostridium botulinum. If the lids are puffed up then they definitely are not safe. Perhaps the tomatoes are acidic enough. Open a jar and test with a pH strip or meter.

That should give you the proper information. Out of the range toss.

#5 pep.

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Posted 04 November 2012 - 03:21 PM

Boiling takes care of everything except Clostridium botulinum. If the lids are puffed up then they definitely are not safe. Perhaps the tomatoes are acidic enough. Open a jar and test with a pH strip or meter.

That should give you the proper information. Out of the range toss.


You don't kill the spores by boiling, but what i've read so far, the toxin should be destroyed (as always, depending on temp and time, of course). I guess I'll ask on the MC forum. The pH test is a good idea, though.

#6 radtek

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Posted 04 November 2012 - 03:36 PM

Once present the toxin cannot be removed or destroyed by boiling or pressure cooker temps. The primary reason for pressure canning is to kill the spores of Clostridium botulinum before they can start to spread. The toxin is the by-product much as alcohol is the by-product of yeast. So are gasses. Sustained temperatures above 212F will destroy the spores. Simple boiling will not accomplish this even if it was for hours- which I may add would ruin your canned goods.

Clostridium botulinum is nothing to fool with since it is present in almost everything including meat. Normally it isn't an issue but canning in particular creates the perfect environment for the spores to grow and multiply- specifically if the pH isn't low enough (below 5.0 at least!) and if the temperature was not raised above boiling somewhere around 230F for at least 15 minutes. They like an airless, neutral warm environment which a canned good provides if proper measures are not taken.

#7 Chris Hennes

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Posted 04 November 2012 - 06:10 PM

Is botulism actually the main concern here? If the food wasn't actually canned then you probably don't have an airtight seal and you haven't removed the air from the headspace of the jar to begin with. In that case I'd be more concerned about aerobic bacteria, potentially even introduced well after the food was cooked due to the poor seal.

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#8 Lisa Shock

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Posted 04 November 2012 - 08:58 PM

I'm guessing that there could be an entire buffet of bad things here, mirroring the series of bad procedures and incorrect equipment decisions.

Jar lids are not designed to be re-used. Canned foods need to boiled for precise times based upon the altitude. Jars and lids need to be sterilized and used immediately. Sterile equipment (ladles, jar lifters, tongs, etc.) needs to be used with the sterile jars. Gloves are recommended. Low acid foods must be canned in a pressure canner.

http://www.pickyouro...qa_pressure.htm

Also, remember that modern tomatoes aren't very acidic. The canning guidelines put out by the FDA were changed because tomato types developed in the past 15 years or so are significantly different from those of the past. In other words, the canning guidelines someone may have learned in the past are no longer accepted. And, mixing other veg with the tomatoes probably raised the pH, possibly to a dangerous level.

There's also the issue of degraded quality if the seal isn't true. The food is probably decayed to some degree from exposure to air, even if it isn't contaminated, and simply not all that nutritious. Next time, encourage her to freeze the food.

Overall, I am sensing a generally cavalier attitude towards a process which has well documented procedures which if not followed precisely are known to have fatal results on a consistent basis. Maybe she's been lucky all these years with just doing as she pleases. I only hope that she has enough sense to just consume these items herself and not feed them to others.

#9 pbear

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Posted 04 November 2012 - 09:20 PM

FWIW, pep is right about botox being heat liable. For example, the CDC says, "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." That said, there are so many things that could have gone wrong here that I wouldn't take the chance.

#10 radtek

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Posted 04 November 2012 - 09:43 PM

Wow that is a first for me. If the USDA and the CDC and FDA say toxin infected food is safe after boiling for ten minutes who am I to argue? :unsure:

I must say that on "ehow" the info is contradictory, which I was glad not to see in the govt websites:

Boil infected food and containers for 30 minutes. Low-acid food that has been stored and appears to have been infected with botulinum should be boiled fully submerged for at least 15 and up to 30 minutes, which is enough to destroy any botulinum toxin and kill the bacteria.
Under no circumstances, however, should such food be eaten or its storage containers reused. Discarding the food and containers without boiling creates a risk that the bacteria and its spores can pass to pets, other people or kitchen surfaces.


Read more: How to Destroy Botulism Toxin in Low Acid Foods | eHow.com http://www.ehow.com/...l#ixzz2BJrhbaEB



From the FDA:

When C. botulinum grows it can produce a potent toxin, which can cause death by preventing breathing. It is one of the most poisonous naturally occurring substances known. The toxin can be destroyed by heat (e.g. boiling for 10 minutes), but processors cannot rely on this as a means of control.


I for one- if there suspicion of botulism toxin presence in any food due to observable signs i.e. wrong pH, poor preparation/treatment or bulging lids/cans it's going in the trash. When in doubt toss it out!

#11 Baselerd

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Posted 05 November 2012 - 12:03 PM

I think that falls under the "best practices" category. It would be pretty ill advised if the FDA were to clear the use of infected materials as long as they were boiled before sale...

#12 aberwacky

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Posted 05 November 2012 - 12:20 PM

I would toss it all. They weren't even boiling-water-bath canned, much less pressure canned (which is the appropriate way to process mixed vegetables like these). Why even take the chance?

This is a great resource for canning inforamation: http://nchfp.uga.edu/how/can_home.html. Some of it is a belt-and-suspenders approach, true, but I follow their recommendations. I can hundreds of jars of things every year, and have to toss some if the seal fails, etc. It hurts to do it, but when it comes to food safety, better safe than sorry.

Leigh