Preserving Tomatoes: A Primer

Learn the basics of water bath canning tomatoes, and store your crop with these simple recipes for canning tomatoes and oven-drying them.

Tomatoes

Preserve your tomato crop by water bath canning and drying, two methods that are possible without a lot of equipment on-hand.

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Tomatoes are one of the first foods that many people try to can, partly because water bath canning tomatoes is relatively easy. However, gone are the days when you could simply smash some raw tomatoes into a canning jar, process them in a boiling water bath for a while, and call it done. To can modern tomato cultivars safely in a boiling water bath, you may need to add some acidity. Here’s why.

Over the past several decades, many tomato cultivars have been bred for sweetness. Old-fashioned tomatoes had enough natural acidity that you could safely can them without any other ingredients, but many of today’s tomato cultivars require added acid to bring their pH low enough for canning. Some heirloom tomato cultivars may technically be OK to can without adding acid; however, it’s better to be safe.

Adding acidity. Per pint jar of tomatoes, add 1 tablespoon of bottled lemon juice or 1/4 teaspoon of citric acid. For quart jars, double those amounts. I don’t really notice a difference in the taste, but if you’re worried that it might be too sour, you can add a little sugar to offset the added acidity. Use bottled lemon juice. I know, I know — fresh citrus juice always tastes better, and that's what I use for regular cooking. But in this case, it’s not about flavor — it’s about food safety, and bottled lemon juice has a consistent level of acidity that fresh lemons don’t always have.

You may come across old instructions for canning pasta sauces and other tomato-based products that say tomatoes may be safely canned in a boiling bath due to their acidity. But, again, this is no longer considered safe.

Raw Pack Tomatoes and Hot Pack Tomatoes

To raw pack tomatoes, you simply crush chopped-up raw tomatoes, put them into clean jars, add acid (and sometimes hot water), and then process them in a boiling water bath. It's certainly the easiest way to can tomatoes, but it's also my least favorite. The disadvantages of the raw pack method are longer processing times and a watery product that tends to separate after it cools in the jars (the red pulp floats unattractively above a layer of almost clear, yellowish liquid). But if you really need to get your tomato-canning project done in a hurry, raw pack is better than not canning any tomatoes at all. Despite the longer processing time, it’s still slightly quicker upfront than the other methods.

To hot pack tomatoes, you boil or roast tomatoes for a few minutes before canning. Also, hot pack is almost as easy as raw pack and results in a less watery product that doesn’t separate as much.

If you’re completely new to water bath canning and would like a step-by-step guide to using a water bath canner or large stockpot, see the publications listed under “Canning Resources” at the end of the article.

Water Bath Canning at High Altitudes

The majority of people on this planet live at 1,000 feet above sea level or lower. At those altitudes, water boils at 212 degrees Fahrenheit, and canning recipes generally assume that you’re at an altitude where that’s the temperature of your boiling water bath. But at 2,500 feet, water boils at a little over 207 degrees. Because of this difference, if you live more than 1,000 feet above sea level, you’ll need to adjust the canning times given in boiling water bath recipes. Pressure canning at high altitudes is a different adjustment. See the charts included with each of the recipes for canning tomatoes below, and make sure you choose the correct processing time for your altitude.

Introduction by Leda Meredith, from Preserving Everything.

Canned Crushed Tomatoes (With No Added Liquid)

Canned crushed tomatoes are a high-quality product ideally suited for use in soups, stews, and casseroles. An average of 22 pounds is needed per canner load of 7 quarts; an average of 14 fresh pounds is needed per canner load of 9 pints.

Wash tomatoes and dip in boiling water for 30 to 60 seconds or until skins split. Then, dip tomatoes in cold water, slip off the skins, and remove the cores. Trim off any bruised or discolored portions and quarter the tomatoes. Heat one-sixth of the quarters quickly in a large pot, crushing them with a wooden mallet or spoon as they’re added to the pot. This will exude juice. Continue heating the tomatoes, stirring to prevent burning. Once the tomatoes are boiling, gradually add the remaining quartered tomatoes, stirring constantly. These remaining tomatoes do not need to be crushed. They’ll soften with heating and stirring. After you've added all the tomatoes, boil gently for 5 minutes. Add 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid per pint jar. For quarts, double those amounts. Add 1 teaspoon of salt per quart to the jars, if desired.

Fill hot jars immediately with hot tomatoes, leaving a 1/2-inch headspace. Remove air bubbles and adjust headspace if needed. Wipe the rims of the jars with a dampened clean towel. Adjust lids and process according to the chart, as processing times vary by altitude.

Processing Times for Crushed Tomatoes (Hot Pack)

0 to 1,000 feet: Pint jar 35 min. / Quart jar 45 min.

1,001 to 3,000 feet: Pint jar 40 min. / Quart jar 50 min.

3,001 to 6,000 feet: Pint jar 45 min. / Quart jar 55 min.

Above 6,000 feet: Pint jar 50 min. / Quart jar 60 min.

Whole or Halved Tomatoes Packed in Water

An average of 21 pounds is needed per canner load of 7 quarts; an average of 13 pounds is needed per canner load of 9 pints.

Wash tomatoes. Dip them in boiling water for 30 to 60 seconds or until skins split; then, dip them in cold water. Slip off the skins and remove the cores. Leave whole or halve the tomatoes. Add 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid per pint jar. For quarts, double those amounts. 

Add 1 teaspoon of salt per quart to the jars, if desired. For hot pack tomatoes, add enough water to cover the tomatoes in a stockpot, and boil them gently for 5 minutes. Fill hot jars with hot tomatoes or with raw, peeled tomatoes. Add the hot cooking liquid to a hot pack tomatoes (or hot water to raw pack tomatoes) to cover, leaving a 1/2-inch headspace. Remove air bubbles and adjust headspace if needed. Wipe the rims of the jars with a dampened clean towel. Adjust the lids and process according to the chart, as processing times vary by altitude.

Processing Times for Whole or Halved Tomatoes in Water (Hot and Raw Pack)

0 to 1,000 feet: Pint jar 40 min. / Quart jar 45 min.

1,001 to 3,000 feet: Pint jar 45 min. / Quart jar 50 min.

3,001 to 6,000 feet: Pint jar 50 min. / Quart jar 55 min.

Above 6,000 feet: Pint jar 55 min. / Quart jar 60 min.

Whole or Halved Tomatoes Packed Raw

See Whole or Halved Tomatoes Packed in Water, above, for quantities. Wash tomatoes. Dip in boiling water for 30 to 60 seconds or until skins split, and then dip in cold water. Slip off skins and remove cores. Leave whole or halve. Add 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid per pint jar. For quarts, double those amounts. Add 1 teaspoon of salt per quart, if desired. Fill hot jars with raw tomatoes, leaving a 1/2-inch headspace. Press tomatoes until spaces between them fill with juice. Leave a 1/2-inch headspace. Remove air bubbles and adjust headspace if needed. Wipe jars with a dampened clean towel. Adjust lids and process according to the chart for raw pack tomatoes, as processing times vary by altitude.

Processing Times for Raw Whole Tomatoes Without Added Liquid (Raw Pack)

0 to 1,000 feet: Pints or quarts 85 min.

1,001 to 3,000 feet: Pints or quarts 90 min.

3,001 to 6,000 feet: Pints or quarts 95 min.

Above 6,000 feet: Pints or quarts 100 min.

Water Bath Canning Tomato Sauce

For water bath canning tomato sauce that’s thin, about 35 pounds is needed per canner load of 7 quarts; about 21 pounds is needed per canner load of 9 pints. For water bath canning thick sauce, about 46 pounds is needed per canner load of 7 quarts; about 28 pounds is needed per canner load of 9 pints.

Wash tomatoes, remove stems, and trim off bruised or discolored portions. To prevent juice from separating, quickly cut about 1 pound of fruit into quarters and put directly into a saucepan. Heat immediately to boiling while crushing. Continue to slowly add and crush freshly cut tomato quarters to the boiling mixture. Make sure the mixture boils constantly and vigorously while you add the remaining tomatoes.

Simmer in a large-diameter saucepan until the sauce reaches desired consistency. Boil until the volume is reduced by about one-third for thin sauce, or by one-half for thick sauce. Add 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid per pint jar. For quarts, double those amounts. Add 1 teaspoon of salt per quart to the jars, if desired. Fill hot jars, leaving a 1/4-inch headspace. Remove air bubbles and adjust headspace if needed. Wipe the rims of the jars with a dampened clean towel. Adjust lids and process according to the chart, as processing times vary by altitude.

Processing Times for Standard Tomato Sauce (Hot Pack)

0 to 1,000 feet: Pint jar 35 min. / Quart jar 40 min.

1,001 to 3,000 feet: Pint jar 40 min. / Quart jar 45 min.

3,001 to 6,000 feet: Pint jar 45 min. / Quart jar 50 min.

Above 6,000 feet: Pint jar 50 min. / Quart jar 55 min.

Canning recipes adapted from the United States Department of Agriculture (USDA).


Paste Tomato Cultivars

Paste tomatoes, also called “canning tomatoes,” have dense flesh and little juice, so they’re the best type for cooking, canning, and drying.

‘Orange Banana.’ Banana-shaped, fruity, and sweet, their orange color is rare among paste tomatoes.

‘Amish Paste.’ Bright red, Roma-type tomatoes that originate from an Amish community in Wisconsin. They're considered to be the ultimate paste tomato.

‘Martino’s Roma Tomato.’ These tomato plants require little staking and are resistant to early blight; plum-shaped fruits are very meaty, suited for sauces, salsas, and pastes.

‘Black from Tula.’ A Russian heirloom that's brownish-red in color, this tomato has a flattened-globe shape.


Canning Resources

National Center for Home Food Preservation (NCHFP)
USDA Complete Guide to Home Canning, available at NCHFP website
The All New Ball Book of Canning and Preserving, published by Oxmoor House and available from the Heirloom Gardener store.


Try preserving tomatoes with your oven, too:

Oven-Dried Tomatoes