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Canning -- Miscellaneous

Do you need to acidify all home canned tomato products?

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The pH of tomatoes is usually below 4.6. Sometimes the pH might vary - depending on the cultivar, growing conditions, maturity, or condition, such as diseased or frost-bitten. So it is recommended to slightly acidify by adding an acid - vinegar or lemon juice. The following information about pH values was reported in the text, Food Preservation and Safety: Principles and Practice. Underripe red tomatoes average pH 4.19; ripe, 4.35; and overripe, 4.38. Underripe yellow color tomatoes averaged pH 4.02, ripe, 4.20; and overripe, 4.33. Underripe orange color tomatoes averaged pH 4.17; ripe, 4.25; and overripe, 4.33. In fact, other information that I have collected shows that it is very rare to have a tomato with a pH greater than 4.6. Therefore, acidification is simply a way to err on the side of safety; theoretically it is not a necessity. Secondly, the processing times for tomato products in a pressure canner are nearly double those for fruits, which have comparable pH values. Fruits that are processed in a pressure canner are not acidified. Therefore, processing for the recommended times and pressures in the Complete Guide to Home Canning would be safe for a non-acidified tomato processed in the pressure canner.

PREPARED BY: Angela M. Fraser, Ph.D., Associate Professor/Food Safety Specialist, NC State University in July 2004

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