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Sep 1, 2009 12:40 AM

pH test kits for home canning tomatoes?

We've got a home canning work party to put up tomatoes scheduled for friday. But the participants are having a raging debate about whether we need to add citric acid complying with USDA recommendations or go with the classic Italian methods of just tomatoes and salt. We're using San Marzano variety, which potentially fall into the danger zone of lower acid.

I was hoping to get my hands on an inexpensive and accurate for our range (ph of 4.6 +/- 0.5) that would allow us to test each batch and decide whether an acid addition was needed or not. Potentially those would be the lots that we decide to freeze instead of can. Since the event is this week, I need something readily available and wondered if there might be some kind of medical home testing, swimming pool supplies, etc. that would be suitable. Ideas?

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  1. Melanie,
    Here is a link that might help you out. They carry a kit for a PH of 3-6 which should cover your range. I never pressure can tomatos and always use 2 Tablespoons of Nellie & Joes key lime juice in my San Marzano's or Romas. I hope this helps and that you will share your results.
    BTW These strips are very similar to what we run through commercial dish machines to test heat and chemical balance. We use them in pot sinks as well.

    Best Regards,

    3 Replies
    1. re: Fritter

      Thank you, really helpful to know that a product exists. Now, if I can find it locally, as the shipping cost to get them here by friday morning was prohibitive. I've struck out at medical supply houses, but hope I can find such at a home winemaking/brewing store. So far only a handheld pH meter, lowest priced one at $90.

      Edited to add: Is there a taste preference or other reason why you use key lime juice vs. lemon juice, cider vinegar, etc.?

      1. re: Melanie Wong

        I find the key lime juice goes very well with tomato and does not have a sharp taste like vinegar nor is it as noticeable as lemon can be.

        1. re: Fritter

          Thanks, the regional thread I linked below includes a report from another 'hound that sourced from the same farm that I'm using. It will be interesting to see how my numbers come out in comparison.

    2. Try a store that sells aquarium supplies.

      1 Reply
      1. re: phofiend

        Thanks, aquarium range tends to be 5 to 9. I had also checked into pool supplies, and those fell in 6 to 8 range.

      2. Here's the thread on the San Francisco Bay Area board and the sources of testing kits we found.

        1. You might want to check health food stores, they usually carry something like this:
          which looks like its in the pH range you want.