pH meters measure the acidity or pH of cottage foods. There are many reliable models in the $50 to $100 range. It is recommended to use one that has at least two calibrations (left example). Some like the model on the right come with kits that also have a storage solution for the probe tip.

pH meters are calibrated every time you use them. You calibrate first, by dipping the probe tip into each calibration solution. Then to test your food sample, you insert the probe tip directly into your food sample.

If your food sample isn't a uniform mass, you will need to blend it first before testing it. For example, a salsa that is liquid with chunks of tomatoes, you'd blend that into a uniform mass first, then test.

You test your canned foods 24 hours after canning them - and write that value down in a test log like this one.