How do I test pH levels before canning?

Craig LeHoullier, PhD
Author of Epic Tomatoes

Decades ago, the USDA carried out a study of tomato acidity (pH) compared with many different sizes, shapes, and colors. The happy results for home canners are that all tomatoes can be considered equally acidic for all intents and purposes. The key objective in home canning, however, is ensuring the safety of the canned product. The addition of an acid source, such as citric acid or lemon juice at the recommended amount—referring to a reliable resource such as the Ball Blue Book—is critical. This proactive addition of acid doesn’t alter the quality of the canned product, ensures safety, and removes the need to do any pH tests before canning.