Using & Preserving Tomatoes

Heirloom Tomatoes

Heirloom Tomatoes

by Cat, Dec 2007; updated Nov 2013 (photo, right, from Wikimedia Commons)

Research has revealed that the nutrient value of tomatoes is increased by cooking (but not by overcooking), so indulge in a good tomato sauce frequently.

The most common types of preserved tomatoes are canned versions of  Tomato Paste, chopped or crushed tomatoes and Tomato Sauce.  I prefer to make all of these at home because using fresh tomatoes is more nutritious, provided you can start with ripe tomatoes. It also allows you to avoid the problem of toxins from welded steel cans and can linings.

Peel, De-seed, and/or Puree Tomatoes

Peeling tomatoes can be a pain, but it is much easier if you first immerse each tomato in a bath of boiling water for 10 to 15 seconds (no longer, or they will be too mushy); alternately you can scorch the skin in a gas flame, but not too long.  Then let them cool before peeling (do not cool in cold water as it will affect the flavor).  The peels should slip off easily. (1,2)

To de-seed the peeled tomatoes, cut each in half around the equator.  Hold each half in the palm of your hand and gently squeeze out the seeds. (2)

Food Mill (Moulinette)

Food Mill (Moulinette)

Puree: It is best not to use a blender or food processor to puree them, as these methods will make them foamy by incorporating air.  Instead, push them through a food mill (see photo, left, from Wikimedia Commons). The food mill has the added advantage of not requiring you to peel them first.


Freeze Homemade Tomato Products

To preserve homemade tomato products, I freeze them:

  • Small portions of tomato paste can be frozen in an ice-cube tray, to keep them handy in the freezer to use as needed.
  • Chopped or pureed tomatoes and tomato sauce can be frozen in pint and quart jars. Just remember to use jars designed for use in the freezer, and to leave an inch of space at the top because they expand as they freeze.

Canned Tomatoes (Heat Process)

Another option is to heat-can them, peeled whole, chopped, crushed, sauce, and/or paste. Although tomatoes are an acid food, they often are not acidic enough to can in a hot water bath (unless you add lemon juice or citric acid), so most recommendations are to use a pressure canner, which I don’t have, and which also is more destructive to the nutrients.

Commercially-Canned Tomato Products

In a pinch, I will use commercially canned tomatoes (whole, chopped, crushed or paste), but I always make my own sauce because I don’t trust the ingredients in commercial tomato sauces. However, commercially canned tomatoes come in welded steel cans rather than glass jars. The weld contains lead, a toxic heavy metal that will readily leach into the acidic tomatoes, so modern cans are lined with BPA, a plastic that is now known to be toxic (carcinogenic).

Muir Glen (3), an Organic brand of canned tomato products, lines their tomato cans with epoxy-enamel, so was believed to be more healthful until it was exposed as being a BPA-containing epoxy. Also note that Muir Glen is now owned by General Mills, one of the major companies opposed to the labeling of GMOs.

Dehydrated & Sundried Tomatoes

I have have no experience with dehydrating foods, but I know this is an excellent way to preserve tomatoes. After dehydrating, they can be kept in a closed container, or in jars with olive oil. I love to use dehydrated or sun dried tomatoes in recipes such as Chicken Penne with Sun-dried Tomatoes.

Refer to The Seasonal Chef (4) or Homecooking at (5) for lots of tips on drying and using dehydrated tomatoes.

Reconstitute Dehydrated or Sundried Tomatoes

  • In oil: place in a bowl and cover with extra virgin olive oil for 24 hours before using.  Save the tomato-flavored oil to use in salad dressings, for example.1
  • In water: Place dried tomatoes in a heat-proof bowl; cover completely with boiling water.  Let sit for 30 minutes until soft and pliable; drain and pat dry.  Reserve soaking liquid to use in soups and sauces.  Refrigerate and use leftover reconstituted tomatoes within 3 days, or cover with oil and refrigerate to use within 2 weeks. 1


  1. Global Gourmet on Peeling Tomatoes:
  2. Nourishing Traditions, by Sally Fallon and Mary G. Enig
  3. Muir
  4. The Seasonal Chef:
  5. Homecooking at

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