Colorado State University Extension
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SPOILAGE IN CANNED FOOD PRODUCTS

By: Stephanie Hoffman, CSU Food Science Graduate Student - Fall 2008

The safety of commercially canned foods is generally not of concern to consumers, but recent national recalls of canned chili products and institutional-size cans of vegetables due to potential contamination with Clostridium botulinum is a reminder that store-bought canned goods can be implicated in foodborne illness outbreaks. These were the first recalls of commercially canned foods in the U.S. linked to botulism in 33 years and improper processing that allowed the survival of C. botulinum spores appears to have been the cause. Home canners and commercial manufacturers both rely on time-tested processes to insure the inactivation of this deadly microorganism. Proper cooking temperatures, times and pressure, along with well-maintained equipment are all necessary to prevent the survival of C. botulinum.

How can consumers help protect themselves? One important way is to look for signs of spoilage and to immediately discard any canned foods that are suspected of being spoiled.

Here are the terms used in the industry to describe canned foods with signs of spoilage:

• Soft Swell: A can that is bulged on both ends, but not so tightly that the ends can't be pushed in somewhat with a thumb press.
• Hard Swell: A can that is so tightly bulged on both ends that the ends can't be pressed in. A can with a hard swell will generally "buckle" before it bursts.
• Flipper: A can whose end normally looks flat, but "flips out" when struck sharply on one end.
• Springer: A can with one end bulged out. With sufficient pressure, this end will flip in, but the other end will flip out.
• Leaker: A can with a crack or hole in the container that has caused leakage.

Flipper and Springer cans do not always indicate microbial spoilage, but are often an indication of contamination. Soft swells, hard swells and leakers usually do represent microbial spoilage but can sometimes be caused by chemical reactions. As always, do not purchase or consume canned food products that are bulging or have packaging that appears compromised in any way. It's always better to be safe than sorry!

Sources:

1. CDC, MMWR, July 30, 2007, Botulism Associated with commercially canned chili sauce - Texas and Indiana, July 2007. 56 (Dispatch): 1-3.
2. FDA/CFSAN. 2001. Chpt. 21A. Examination of Canned Foods. Bacteriological Analytical Manual Online. http://www.cfsan.fda.gov?~ebam/bam-21a.html. Accessed 9/3/2008.
3. Kendall, P. 2006. Botulism. CSU Extension Fact Sheet 9.305.

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