NDSU Extension Service

Ask Extension
for answers to commonly asked questions.

Discoloration in Canned Foods

Date: July 1988 (Reviewed June 1996)

Source: University of Wisconsin

Pink, red, blue or light purple discoloration sometimes occurs in home-canned fruits and vegetables.

This discoloration can happen in canned apples, cauliflower, pears, peaches or beets.

Keep all fruits and vegetables cool after you harvest them and before you can them.

For hot-pack canning, do not overcook or heat at too high a temperature. Excessive heat alters virtually all natural food pigments.

If fruit grows in very dry, hot weather, it often turns pink; you cannot prevent this discoloration.

Cauliflower with a purplish tinge is frequently found in the market and it can be disconcerting for some folks but there's nothing to worry about. Purple cauliflower is safe to eat.

Some cauliflower varieties have a genetic propensity to having a higher concentration of red, purple, or blue pigments. This is the same harmless, water soluble pigment found in eggplant, red cabbage, berries, plums and grapes. In other types of cauliflower the colorless or white pigments will predominate. Purpling can develop in white varieties of cauliflower if the heads are exposed to light while developing. Usually, the leaves are tied over the heads.

If the cauliflower has a lot of purpling it is probably best to use it raw for relishes or salads. Heat may induce a color change from purple to gray or slate blue--especially if the water is hard or had an alkaline pH. If you prefer to have cooked cauliflower add a little vinegar or cream of tartar (tartaric acid) to the water.

Red pigments in beets fade if the beets are overcooked before canning or overprocessed during canning.

Although it may not be appetizing, you can eat the food if the liquid is clear, the odor is natural, and if you used the recommended processing methods, time and temperature.

If you used garlic in a product and the garlic has an iridescent greenish coloring, this is the result of using immature garlic--it was not completely dry.

Store canned foods in a cool, dark place.

If you have further questions, contact your county office of the NDSU Extension Service.

Back to Canning Menu
Go to Ask Extension Index Page
For More Information
Contact your North Dakota County Extension Office of the NDSU Extension Service for additional information or see our main NDSU Web Page for publications and articles on Agriculture, Horticulture, Youth and Family, Business and Community and Food and Nutrition at  http://www.ag.ndsu.nodak.edu/