Home-canned tomatoes are one of my must-have staples.
It’s very hard to find store-bought canned tomatoes and tomato sauce in glass jars… yet due to their acidity, that's a biggie for me. I try to stay away from metal as much as possible.
How To Safely Can Tomatoes
When it comes to canning tomatoes at home, there’s a few things you must know in order to ensure your home-canned tomato products are safe and don’t come with a side of botulism.
First, never can tomatoes that have been through a frost. Frost significantly lowers acidity, so these tomatoes are not considered safe for canning.
Second, although tomatoes are considered an acidic food, their pH must be 4.6 or lower to be safe for water bath canning. Because they are technically a fruit, we are able to water bath can tomatoes. (All vegetables, unless pickled, must be pressure canned to avoid botulism.)
Tomatoes aren't as low on the pH scale as some people think.
The Myth About Heirlooms & Acidity
Tomatoes are borderline — falling between a 4.30 and 4.90 on the pH scale (source).
Many people falsely believe that an heirloom tomato is more acidic, so if they’re growing and using heirloom tomatoes, they don’t need to add additional acid.
Testing has confirmed that this is not the case. In fact, some heirloom varieties aren’t as acidic as hybrids. Don’t rely on the type of tomato as your guide for its acid content.
All home-canned tomatoes, including tomato sauce, tomato juice, and tomato paste should have a form of acid added to them — even when pressure canned. The tested times and recipes for pressure canned tomatoes are with added acid, not without.
Types Of Acid For Home-Canned Tomatoes
There are 3 types of acid to add to your home-canned tomatoes. No matter which acid you choose, it should be added to each individual jar to ensure proper acidity.
The 3 types of acid for home-canned tomatoes are:
- Citric acid
- Bottled lemon juice (not fresh because acidity varies on how the lemon is grown and harvested)
- Vinegar (not homemade vinegar — it must be 5% acidity)
Most people choose not to use vinegar for taste reasons.
Add the chosen acid to the jar before filling with tomatoes to ensure each jar has the proper amount.
- Citric acid: ¼ teaspoon per pint jar and ½ teaspoon per quart
- Bottled lemon juice: 1 tablespoon per pint and 2 tablespoons per quart.
- Vinegar: 2 tablespoons per pint and 4 tablespoons per quart
Home-canned tomatoes are a wonderful addition to your pantry because lycopene, an antioxidant, increases in bioavailability when tomatoes are cooked (source). Sweet, right?
Personally, I love to can tomato sauce. It's so versatile! With home-canned tomato sauce, I then make tomato paste, spaghetti sauce, pizza sauce, or I add it to stews or soups for more flavor.
Do you can tomatoes? Do you use a water bath or pressure can them? Which acid do you prefer?
This post was featured in How to Can Tomatoes 16 Ways.
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