Canning - Tomatoes Acidification
Tomatoes are botanically classified as fruit, but they are commonly thought of as a vegetable. The amount of natural acid in tomatoes varies depending on the variety, growing conditions, maturity and handling. To ensure safe acidity in whole, crushed, or juiced tomatoes, add two tablespoons of bottled lemon juice or ½ teaspoon of citric acid per quart of tomatoes. For pints, use one tablespoon bottled lemon juice or 1/4 teaspoon citric acid. Acid can be added directly to the jars before filling with product. Add sugar to offset acid taste, if desired. Four tablespoons of a 5% acidity vinegar per quart may be used instead of lemon juice or citric acid; however, vinegar may cause undesirable flavor change.