Safely preserve your homegrown tomatoes

BLUE SPRINGS, Mo. — If you’re lucky, you’re getting delicious fresh tomatoes from your garden. If you’re even luckier, you have extra that you want to preserve for the months you can’t walk outside and pick some fresh from the garden.

There are several things to consider when thinking about preserving your tomatoes safely, says Tammy Roberts, a University of Missouri Extension nutrition and health education specialist.

“Vine-ripened, disease-free, firm tomatoes are the best for canning,” Roberts says. Tomatoes aren’t as acidic as they used to be, so you need to add acid to home-canned tomatoes to guard against botulism. Add 2 tablespoons of bottled lemon juice per quart of tomatoes, or 1 tablespoon for pints. You can use 4 four tablespoons of 5 percent vinegar per quart (2 tablespoons per pint) of tomatoes instead of lemon juice, but that can cause undesirable flavor changes.

To remove skins from tomatoes, wash and dip into boiling water for 30-60 seconds or until the skins split. (Dipping them with a cheesecloth pouch works well.) Then dip the tomatoes in cold water, remove the skins and cores and crush, halve or leave whole.

Whole, halved or crushed tomatoes can be hot- or raw-packed and processed in a pressure or boiling-water canner.

“Pressure-canned tomatoes don’t look as pretty as tomatoes canned in boiling water, but the pressure-canned tomatoes are a higher-quality, more nutritious product,” Roberts says. You can add 1 teaspoon of canning salt if desired. Leave half an inch of head space.

If using the pressure canner method, crushed tomatoes should be hot-packed. Pints and quarts can be processed for 20 minutes at 6 pounds of pressure, or for 15 minutes at 11 pounds of pressure. Hot- or raw-packed whole or halved tomatoes packed in water in pints or quarts can be processed for 15 minutes at 6 pounds of pressure or 10 minutes at 11 pounds of pressure.

To process in a boiling-water canner, whether they are hot- or raw-packed in water, pints should be processed for 40 minutes and quarts for 45 minutes. If you are more than 1,000 feet above sea level, increase that time by five minutes.

Related MU Extension guides:

“Quality for Keeps: Before You Start to Can, Learn the Basics” (GH1451) includes a map showing which parts of Missouri are more than 1,000 above sea level. Download at extension.missouri.edu/p/GH1451.

“Quality for Keeps: How To Can Fresh Tomato Products — Tantalizing Tomatoes” (GH1456) is available for download at extension.missouri.edu/p/GH1456.

To see all guides in MU Extension’s “Quality for Keeps” series, go to extension.missouri.edu/preservation.