University of California Agriculture and Natural Resources released information on Apr. 30 about the importance of acidifying tomatoes during home canning to ensure safety. The guidance explains that added acid is always required when canning tomatoes, as their acidity levels can vary above or below the threshold needed for safe processing.
This topic is important because improper acidity in canned tomatoes may lead to unsafe food preservation practices. The recommendation aims to prevent health risks by instructing home preservers to add citric acid powder, bottled lemon juice, or vinegar with 5% acidity to each jar before processing.
The release states that all tomatoes should be acidified whether they are processed using boiling water/steam canners or pressure canners. “To be safe, always acidify tomatoes, for both boiling water/steam canning and pressure canning processes. Use a scientifically validated recipe from a reputable source, and follow the instructions exactly, which will include information on how much acid to add to each jar being processed.” It also notes that some tomato-based recipes developed as low-acid products require only pressure canning with longer times.
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For further details on proper tomato preservation techniques or other food safety topics, readers are encouraged by UC Agriculture and Natural Resources Master Food Preservers program in El Dorado County—who provided this guidance—to consult resources such as the National Center for Home Food Preservation.