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There is hardly anything more quintessentially southern than tomatoes. Whether used as a base for soups or simply sliced for a good old ‘mater sandwich, tomatoes are true summer favorites. To enjoy their goodness year-round, people can turn to the world of canning as a means of preservation.
“Tomatoes are plentiful this year, and a lot of people are asking questions about how to can them,” said Angela Treadaway, an Alabama Cooperative Extension System food safety and quality regional agent. “There is some misinformation out there, so it is important to know the proper way to safely can your tomatoes.”
Safe Water Bath Canning

Tomatoes are traditionally canned using a method known as water bath canning. This is where lidded jars are immersed into boiling water (212 degrees Fahrenheit) for a set amount of time to kill harmful bacteria and vacuum seal the jars. Other high-acidic foods that use this method include pickled products, jams, jellies and most other fruit products.
To prevent the growth of bacteria that causes acute food poisoning (botulism), canned foods must have a pH level of 4.6 and lower. Today, many of the tomato varieties grown are not as acidic as varieties grown in past years. They typically have a natural pH level between 4.6 and 4.8. This has caused recommendations to change when water bath canning tomatoes.
To reach the correct pH level, foods that are naturally low in acid are usually preserved using the pressure canning method. While there are some tomato products that require this method, the U.S. Department of Agriculture recommends that people simply add acid to tomatoes before water bath canning them. This helps prevent the possibility of food poisoning and other bacterial concerns, all while keeping the traditional preservation method.
Acidifying Tomatoes
There are two options for adding acid to tomatoes before canning. The first and preferred option is adding lemon juice or citric acid. For quart jars, add 2 tablespoons of bottled lemon juice or ½ teaspoon of citric acid. For pint jars, add 1 tablespoon of bottled lemon juice or ¼ teaspoon of citric acid. The second option is adding vinegar.
“You can use vinegar, but it may change the taste of the tomatoes,” Treadaway said. “If you decide to use vinegar, add 4 tablespoons per quart and 2 tablespoons per pint.”
The acidifying and water bath canning combo is not suitable for all tomato products. Ones that still require pressure canning include the following:
• Tomatoes with okra or zucchini
• Spaghetti sauces
• Mexican tomato sauce, where there is little-to-no acid added
• Tomato-based vegetable soups.
It is also essential to use standard canning jars for preserving your harvest.
Use standard canning jars—they generally have the manufacturer’s name in big letters printed on the side of the jar and/or the word MASON. Do not use peanut butter, mayonnaise, or pickle jars, etc., because they may not withstand the 10-pound (240°F) pressure needed to can vegetables. If you are reusing standard canning jars you have on hand, be sure to check your jars for chips or cracks. Run your finger around the mouth of the jar to see if it has any chips or breaks. If it does, the jar will not seal. Jars can be used for years if handled correctly and have no nicks or cracks.
Wash and rinse the jars by hand or in the dishwasher just before you fill them with hot produce to keep them from breaking them. Keep jars warm until ready to place hot product in them.
Canning lids are best if they are the two-piece version.
For more information about proper canning methods, check out the Alabama Extension publication, “Wise Methods of Canning Vegetables,” available at www.aces.edu.
Keep these tips in mind when working to preserve your harvest:
• Use the variety of produce your family likes.
• Select mature, yet tender, vegetables.
• Remember: From the garden to the canner in 2 hours.
• Wash and prepare the vegetable carefully.
• Preheat the vegetable if using hot pack method.
• Pack in standard canning jars; cover with liquid; remove air bubbles.
• Wipe jar mouth and threads; adjust lid according to manufacturer’s instructions.
• Open canner lid away from your face to prevent steam burn. Lift side of canner lid away from you.
• Take out hot jars one at a time.
• Place jars on a rack to cool—out of a draft.
The next day, check lids to make sure they sealed with the lids being concave; clean jars and put away in storage in a clean, dark, dry area for a year to a year and a half.