Any way to check canned tomato safety?

I've canned a few quarts, but I have to admit they make me a little nervous. Any way to check if they're ok before using? Is there a ph that would indicate they're safe to eat after sitting for a while?

  • Posted by: allison
  • August 16, 2021
Grandma's Canned Tomatoes
Recipe question for: Grandma's Canned Tomatoes


Gammy August 16, 2021
Yes, what 702551 said below, and if you push on the center of your canning lid, it should move very little if at all under your pressure. If instead it is easily depressed and possibly make that tell-tale clicking noise, open it up and dispose of the contents. The glass jar and metal ring can be reused once washed and sterilized... examine the ring to see if maybe some of the contents got between the lid and the jar causing that failure. Then dispose of the lid.
702551 August 16, 2021
The pH should be 4.6 or lower (more acidic) to prevent Clostridium botulinum from growing. Here are several sources that all lead back to the USDA's guidelines:

If you don't have a pH meter, you will have to do a visual inspection.

Mason jar lids on a canned product should be concave (sunken in) which indicates a proper seal and no gas production from C. botulinum.

This is the same visual inspection for store-bought canned food (and not just tomatoes): if the can is bulging, it should be discarded to avoid botulism. There is nothing new about this, Gerber baby food fifty years ago was handled the same way, with a pop-up button on the lid that indicated that the food inside should be discarded.

Best of luck.
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