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Canning -- Tomatoes

A can of tomatoes smelled fermented but was not discolored. Is it safe to eat?

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Under-processing of any canned food product could lead to the growth of spoilage as well as pathogenic microorganisms. Tomatoes should be acidified and then processed for between 40 to 85 minutes in a boiling water bath, depending on the form of the tomatoes. Because the tomatoes smell fermented (an alcoholic odor), the spoilage culprit probably is yeast. If food is spoiled due to yeast, it is usually a sign of gross under-processing or leakage. Yeast growth is accompanied by the production of alcohol and large amounts of carbon dioxide gas, which swells the container or causes the lid to bulge. The fact that not all containers were fermented simply indicates that (1) the number of yeast on some of the tomatoes might have been less - they might have been washed better prior to packing; (2) the jars that were not fermented might not have been filled as tightly so heat penetration was better; or (3) the position of the jars in the water bath were such that there was greater exposure to high temperatures. Heating food to 170 F easily destroys yeast. Keep in mind that in canned foods yeast growth itself does not present a significant public health problem. However, when a canned food spoils it usually indicates under-processing or leakage. Therefore, harmful bacteria could be present. Thus, she needs to discard all of the tomatoes that she water bath processed for 15 minutes.

PREPARED BY: Angela M. Fraser, Ph.D., Associate Professor/Food Safety Specialist, NC State University in July 2004

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