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Extension > Food > Food Safety > Preserving and Preparing > Tomatoes and Salsa > Add Acid to Tomatoes Before Processing

Tomatoes and Salsa

Add Acid to Tomatoes Before Processing

By Carol Ann Burtness, Extension Educator — Food Safety Extension

Peer reviewed 2012 by Suzanne Driessen, Extension Educator — Food Safety.

Today, our current varieties of tomatoes are not as high in acid as they used to be. Today, researchers have found that new tomato varieties; stressful growing conditions; or over-mature fruit may affect acid levels. Other factors that affect the acidity level of tomatoes include adding low-acid ingredients to tomatoes such as onion and peppers; making juice versus tomato solids; and the canning process itself. Because many factors impact the acidity level of tomatoes and may support the growth of Clostridium botulinum, USDA recommends adding acid to all home-canned tomatoes and tomato products.

Procedures

Acid can easily be added directly to the jars before filling with tomatoes. Added acid can be either citric acid or bottled lemon juice. Citric acid is available where canning supplies are sold or ordered online.

Added acid can be either
citric acid or bottled lemon juice.

Do not use freshly squeezed lemon juice because the acidity level varies and there is a  chance of contaminating the juice from the rind. Tomato canning tablets that may be found on the market should not be used because they are ineffective.

Add acid to all tomatoes

Acid Effect Amount
Citric acid Little change in flavor 1/2 tsp/quart
1/4 tsp/pint
Bottled lemon juice Easy to use 2 Tbsp/quart
1 Tbsp/pint
Vinegar (5% acidity) Noticeable flavor change 4 Tbsp/quart
2 Tbsp/pint

For more information, check out National Center for Food Preservation

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