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Just because it seals, doesn’t mean it’s safe
North Carolina Cooperative Extension News

Just because it seals, doesn’t mean it’s safe

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We are well into canning season, and many people are looking for answers to their food preservation troubleshooting questions. A common assumption is that as long as the jar seals, it will be preserved and safe to consume. This is not always the case.

Although a good seal is important for a safe canned product, proper processing technique is arguably the most important step. Sealing without proper processing can lead to microorganism growth, spoilage and possible harmful toxin formation.

For instance, jars of canned carrots can be hot packed, but if they are not properly processed at the correct time and pressure as directed by a tested canning recipe, they will most likely spoil. Open kettle, oven canning and other not-recommended forms of canning may produce these, or similar unsafe results. The problem is that there are not always visual signs when a canned product is unsafe for consumption.

The pathogen of concern when canning is Clostridium botulinum, which could cause botulism, a potentially deadly form of food poisoning. These spore forming bacteria can survive harmlessly in soil and water and are very prevalent on the surface of most fresh food surfaces. As anaerobic bacteria, Clostridium botulinum spores only become dangerous in environments with an absence of oxygen, making them harmless on fresh food surfaces.

In certain conditions, C. botulinum spores can produce vegetative cells that rapidly multiply and produce a deadly neurotoxin within three to four days of growth. Ideal conditions for C. botulinum growth consist of: a moist, low acid food, a temperature between 40 degrees and 120 degrees and less than 2 percent oxygen. You can see by these criteria that improperly processed home canned goods exhibit the perfect environment for C. bot growth.

Don’t let the fear or inconvenience of proper processing of canned goods be a reason to compromise the safety of your friends and family. Just because it seals, doesn’t mean it’s safe.

For questions about proper canning methods and procedures, contact Emily Troutman at or 828-764-9480.

Emily Troutman is an Extension agent specializing in Family and Consumer Sciences for Burke County. Contact her at 828-764-9480 or The North Carolina Cooperative Extension — Burke County Center is located at 130 Ammons Drive, Suite 2 in Morganton. For more information, visit

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