Questions about Canning Tomatoes- - U of I Extension

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Questions about Canning Tomatoes-

This article was originally published on August 22, 2008 and expired on September 22, 2008. It is provided here for archival purposes and may contain dated information.

Following last week's column on canning tomatoes, I received several calls related to tomatoes separating from the liquid.

Why do my tomatoes separate from the liquid?

A frequent problem is the separation of water from the tomatoes. Why does the water separate from the solids in tomatoes?

Scenario 1 - liquid at the top and solids at the bottom

Home canned tomatoes, tomato juice, and tomato sauces with liquid at the top and solids at the bottom are quite normal. It only reflects that the juice was made prior to heating. For example, the tomatoes were chopped, run through the steamer, sieve, or food mill while still raw and prior to heating.

As soon as they are chopped or crushed, enzymes start to break down the pectin that helps to hold tomato cells together. The enzyme that causes separation is activated by exposure to air and inactivated by heat. In commercial production, tomatoes are flash heated nearly to boiling in a matter of seconds, using equipment not available to consumers. Because the pectin holding tomato cells together is not exposed to air when cold, it remains intact, and a thick bodied, homogeneous juice is produced.

The solution is to leave tomatoes whole or in large chunks (do not chop). Heat before chopping or juicing to minimize the separation.

The best way to do that at home is to heat quartered tomatoes quickly to boiling temperatures WHILE crushing. You can also heat the blanched, peeled whole tomatoes in the microwave, then crush them!

Make sure the mixture boils constantly and vigorously while you add the remaining tomatoes. Simmer 5 minutes after all tomatoes are added, before juicing. If you are not concerned about juice separating, simply slice or quarter tomatoes into a large saucepan. Crush, heat and simmer for 5 minutes before juicing.

Scenario 2 - liquid at the bottom and solids at the top

What about the reverse: liquid at the bottom and solids at the top? That indicates too much preheating (more than 5 minutes). Pectin breaks down when it is overheated; then separation results. If separation occurs, just shake the jar before opening or decant the water off.


4 cups peeled, cored, chopped tomatoes (about 2 ½ pounds)

2 cups seeded, chopped green peppers (about 1 pound)

1 cup seeded, chopped hot peppers (about ½ pound)

¾ cup chopped onion

1 teaspoon salt

2 cloves garlic, minced

1 ½ cups cider vinegar

Combine all ingredients in a large saucepan. Bring mixture to a boil. Reduce heat and simmer about 20 minutes. Pour hot into hot jars, leaving ¼-inch head space. Adjust lids. Process 30 minutes in boiling water canner. Yield: about 6 half-pints.

For milder salsa, select mildly hot peppers. For hot salsa, use jalapeno, Serrano, or other very hot variety peppers.

Caution: Wear rubber gloves while handling hot peppers, and avoid touching face or eyes.


Pull date: September 22, 2008