Molly53
Sun Jan 13, 2013 10:22 am
Forum Host
Hi, and welcome to our forum, friend!
Color changes can be the result of several factors. How do you can your tomatoes? Do you pressure can? Do you add bottled lemon juice or citric acid?
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CANNING TOMATOES for the NCHFP (National Center for Home Food Preservation) guidelines.
What makes canned foods change color?
Oxidation may cause foods to darken at the tops of jars. Oxidation is from air in the jars or too little heating or processing to destroy enzymes.
Overprocessing may discolor foods throughout the containers. Pink and blue colors sometimes seen in canned pears, apples, and peaches are caused by chemical changes in the coloring matter of the fruit. Iron and copper from cooking utensils (or from water in some locations) may cause brown, black, and gray colors in some foods. When canned corn turns brown, the discoloring may be because of the variety of the corn, the stage of ripeness, overprocessing, or copper or iron pans. Packing liquid may dissolve coloring materials from the foods.
The pigments in food which are responsible for their colors are sensitive to a variety of things which they may come into contact with during home food preservation. Acids (lemon or other fruit juices), anti-caking ingredients in table salt, minerals in water, metals in water and from cooking utensils, heat, and light are a few things which can affect these pigments causing them to change color.
Sometimes tomato juice and other juices will separate if there is an enzymatic change during the handling of the tomatoes (or fruit) after it has been cut. The best way to prevent this is to heat the tomatoes quickly to a simmering temperature.
Is it safe to eat discolored canned foods?
The color changes noted do not mean the food is not safe to eat. Spoilage, however, may also cause color changes. Before you use any canned food that has an unusual color, examine it carefully.
Signs of Spoilage:

Bulging jar lids, or a leak, may mean gas is present and the food spoiled.

Before opening home canned foods wash jars and lids and carefully inspect the jars. Bacteria, yeasts and molds should have been destroyed if the food was properly processed.

When you open the container, look for such danger signs as spurting cloudy or frothy liquid, an "off" color, deterioration, or slimy texture. A foamy or murky appearance and patches of mold are visible signs of spoilage. That ordinary looking mold on home- canned food may indicate the presence of a much more deadly problem: botulism.

The odor in good jars of food should be pleasant and characteristic of the product. Do not use food which looks or smells bad, or if there is any doubt as to its safety.

Destroy food if any of these signs are obvious; discard out of reach of humans and animals.

All low-acid, home-canned food should be boiled 10 to 20 minutes to ensure destruction of botulism-causing toxin for added safety. Heating denatures the toxin so that it does not react with the body. Never taste low-acid, home canned food before cooking it.[/I]