Food safety and botulism indicators for pressure canned goods


Several months ago I canned some ham and pea soup, following this recipe verbatim. All went well and the jars have been sitting in my dark pantry ever since.

This was my very first time (ever) using a pressure canner, and so I have no idea what to expect. I'd like to crack one of the jars open and have some pea soup for dinner this week. At first glance, everything looks ok:

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But then I noticed there is a lighter green (slimy looking) film on the very top of the soup:

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Is this normal, or does this mean its gone bad?

More generally, with pressure canning recipes, what is a good way to tell if the food is safe to consume?

I've heard of the following approach:

  1. Open the lid and confirm you hear the popping sound (the seal breaking), and let it sit in the open for a few minutes, then put the lid back on and put it in the fridge
  2. Wait a day, take it out and inspect
  3. If there is any white foamy substance that sprung up overnight (strong indicator of botulism) or if there are strong off-putting odors, toss it
  4. Otherwise have a bite and wait a day
  5. If by the next day you haven't developed any upset stomach or other GI issues, it is very likely safe to consume the rest

Is this a safe system to follow here? Any other practices or methods anybody can think of? Thanks in advance!

Best Answer

The layer on the top is either separated fat from the ham and bouillon cubes, or a bacterial and/or fungal growth (aka a "pellicle"). If it feels greasy and/or brittle and becomes transparent when heated, it was just fat. If it feels rubbery and maintains its coherence when heated, it was a pellicle. A pellicle is not an indication of a botulinum infection, but it's definitely an indication that you screwed up the canning process and that the contents are inedible.

There is no way for a home cook to determine if a can of food is safe to eat. That would require special expertise and lab work (including, when testing for botulism, injecting mice with the stuff). Instead, what you do is use a trustworthy recipe, make sure you're following the recipe properly (with a canner that reaches the appropriate pressure for the appropriate amount of time), and check that the vacuum seal has not been compromised before eating. That is, rather than seeing whether the food is safe, you ensure that your process guarantees safe food.

The steps you posted are horrible -- neither safe, nor effective, and betraying a fundamental misunderstanding of what botulism even is -- and you should no longer trust whoever wrote them. "Have a bite and wait a day"? Cripes on a cracker.