Enjoy tomatoes all year long

Canning, freezing, or dehydrating are the three safe methods for preserving, and each has a specific set of instructions yielding a unique product. You'll want to read the full guidelines for Processing Tomatoes from Illinois Extension.

Selecting your tomatoes

  • Choose only firm, disease-free, ripe, or under-ripe tomatoes. Overripe tomatoes are too low in acid to safely can.
  • Green, under-ripe tomatoes, or heirloom tomatoes may be used following the same directions as ripe, red tomatoes.
  • Do not can tomatoes from dead or frost-killed vines, as they may be too low in acid. Freeze or dehydrate instead.

Removing Tomato Skins 

Most recipes, whether canned, frozen, or dried, will call for peeled tomatoes. When canning, if the recipe says to peel the tomato, then you must peel it, as the processing time is based on a peeled tomato.

  • Wash tomatoes under cool running water.
  • Dip them in boiling water for 30 to 60 seconds. A little trick: before dipping in boiling water, you may take a paring knife and slit an “X” on the bottom of the tomato. It may help it start to peel off. Do not leave the tomatoes in boiling water for too long! They will become mushy.
  • Dip in a bowl of ice water.
  • Slip off the skin and remove the core. Leave whole, halve, chop, or whatever your recipe calls for.

Canning Tomatoes

There are only two safe methods of canning: boiling-water bath canning and pressure canning. Tomatoes can be safely canned using either method, but if the recipe provides directions only for the pressure canning method, use only that method.

Boiling-water bath canning

  • Uses pot of boiling water (212°F).
  • Used for acid foods: fruits, jams, jellies, tomatoes and figs with acid added, pickled products, and fermented products.

Pressure canning

  • Uses pressure canner (at least 240°F).
  • May be a dial or weighted gauge.
  • Must be used for low-acid foods, such as meats, vegetables, broth, dried beans, and mixed products.

Adding Acid

Due to the many varieties of tomatoes and the uncertainty of their acidity level, acid must be added
to tomatoes, even when pressure canning. Choose one acidifier option to add to each canning jar before adding the tomatoes and liquid.

  • Bottled Lemon Juice: add 1 Tablespoon per pint; add 2 Tablespoons per quart
  • Citric acid: add 1/4 teaspoon per pint; add 1/2 teaspoon per quart
  • Vinegar* (with 5% acidity): add 2 Tablespoons per pint; add 4 Tablespoons per quart
  • Salt** (optional): add 1/2 teaspoon; add 1 teaspoon per quart

*Vinegar may have an undesirable flavor. **Salt is used only for flavor, not to prevent spoilage.

Packing Tomatoes

No added liquid

Wash tomatoes, take off skins, and core. Add acid to jars. Press tomatoes into jars until remaining space between fills up with the juice released from the pressed tomatoes. Remove air bubbles, leave ½-inch headspace, wipe rims, and add lids.

Process in boiling water bath

  • Pint: 85 minutes
  • Quart: 85 minutes

Process in pressure canner (dial gauge = 11 lbs.)

  • Pint: 25 minutes
  • Quart: 25 minutes

Packed in water

Wash tomatoes, take off skins, and core. Add acid to jars. Choose either raw pack or hot pack:

  • Raw pack: Pack tomatoes tightly in jars and fill with boiling water.
  • Hot pack: In a saucepan, cover tomatoes with water, and gently boil for 5 minutes. Pack tomatoes and liquid in jars.

Remove air bubbles, leave ½-inch headspace, wipe rims, and add lids.

Process in boiling water bath

  • Pint: 40 minutes
  • Quart: 45 minutes

Process in pressure canner (dial gauge = 11 lbs.; weighted gauge = 10 lbs.)

  • Pint: 10 minutes
  • Quart: 10 minutes

Packed in tomato juice

Wash tomatoes, take off skins, and core. Add acid to jars. Choose either raw pack or hot pack:

  • Raw pack: Pack tomatoes tightly in jars and fill with heated tomato juice.
  • Hot pack: In a saucepan, cover tomatoes with juice, and gently boil for 5 minutes. Pack tomatoes and liquid in jars.

Remove air bubbles, leave ½-inch headspace, wipe rims, and add lids.

Process in boiling water bath

  • Pint: 85 minutes
  • Quart: 85 minutes

Process in pressure canner (dial gauge = 11 lbs.; weighted gauge = 10 lbs.)

  • Pint: 25 minutes
  • Quart: 25 minutes

Tomato Juice

Use pints or quarts; do not use half-gallon or larger jars. Just like when canning tomatoes, you will need to add acid, using the same instructions.

Canning Salsa 

While there are many delicious, homemade salsa recipes (and other tomato-based products), only use canned salsa recipes that have been tested for safety in a commercial laboratory. Other recipes may be safely frozen but not canned.

Do

  • Change the type of onion or pepper.
  • Omit or change the type and/or amount of herbs and spices, including salt.
  • Add sugar to overcome tartness.
  • Substitute bottled lemon juice for 5% acidity vinegar.
  • Thicken salsas with flour, cornstarch, or other starches after opening for eating.

Do Not

  • Do not change the amount of onion or pepper.
  • Do not alter the amounts of acid.
  • Do not use fresh lemon or lime juice or vinegar that is NOT 5% acidity level.
  • Do not substitute vinegar for bottled lemon juice.
  • Do not thicken salsas with flour, cornstarch, or other starches before canning.

Freezing Tomatoes

Unlike most vegetables, tomatoes do not have to be blanched, and while you don’t have to take the skins off for freezing them, many people prefer them without the skins. Tomatoes and tomato products which will be frozen do not need to be acidified.

Containers for freezing

Use freezer-safe containers made with plastic or glass, such as plastic freezer containers with tight-fitting lids or wide-mouth canning jars. Do not use regular glass jars; they break easily at freezer temperatures.

Plastic freezer bags are another suitable option. Press to remove as much air as possible before closing.

Before freezing, label the wrapping or airtight container with the product name, current date, and recommended storage time. For best quality, use frozen tomatoes within 10 to 12 months. However, they will remain safe after that.

Freezing raw tomatoes

  • Wash, take off skins and core; leave whole or in pieces.
  • Pack into freezer containers or freezer-safe plastic bags, leaving 1-inch of headspace.
  • Seal and freeze.
  • Freezing juice and mixtures
  • Prepare product according to recipe (may use a canning recipe).
  • Cool and pour into freezer containers, leaving
  • 1-½ inches of headspace.
  • Seal and freeze.

Freezing other variations

  • Stewed tomatoes: simmer in water for 10 to 20 minutes.
  • Green tomato slices for fried green tomatoes (leaving skins on).
  • Cherry or grape tomatoes: roast with a bit of olive oil in a 450°F oven for 20 to 25 minutes until they blister and split.

Drying Tomatoes

Dehydrated tomatoes are packed with tomato flavor! The best tomatoes for drying are Roma, or another type of paste or meaty tomato or grape and cherry tomatoes.

Drying methods

Two methods are recommended for drying tomatoes. Outdoor home drying is not recommended for meats or vegetables, including tomatoes.

Using an electric dehydrator

Dehydrators are designed to dry foods fast, maintain a temperature of 140°F, and circulate air with a built-in fan.

  • Wash tomatoes, take off skins, and core. You do not need to take off skins of cherry/grape tomatoes.
  • Slice tomatoes into ¼ to ½-inch thick slices, or halve or quarter.
  • Place on drying trays, leaving ½-inch of space between tomatoes.
  • Dry in a dehydrator at 140°F for 10 to 18 hours, turning tomatoes and rotating racks as needed.

Using an oven

Make sure the oven can hold a temperature of 140°F.

  • Wash tomatoes, take off skins, and core. It is not necessary to remove skins of cherry/grape tomatoes.
  • Slice tomatoes into ¼ to ½-inch thick slices, or halve or quarter.
  • Place on drying trays, leaving ½-inch of space between tomatoes.
  • Prop open the oven door 2 to 6 inches to allow air circulation. Take caution: this can be dangerous for small children or pets.
  • Oven drying takes two to three times longer than drying in an electric dehydrator.

Test for doneness

Dry tomatoes until they are slightly pliable. If they feel sticky to the touch, they need more time to dry. You may need to turn tomatoes and rotate racks.

References