One of the best places to go for the latest canning and food preservation information--and to ensure food safety in your kitchen: your
cooperative extension agent.
You can also read detailed articles on Canning Fruits and Vegetables by Sue Weaver and Preserving Fruits and Vegetables (including a recipe!) by Cheryl Morrison.
Common Canning Problems
Here's a list of common canning problems compiled by the Clemson University Extension.
- Loss of liquid from glass jars during processing
This is not a sign of spoilage; do not open to replace liquid. However, if at least half of the liquid is lost, refrigerate the jars and use within two to three days.
- Imperfect seal
Discard food unless the trouble was detected within a few hours. Canned food can safely be recanned if the unsealed jar is discovered within 24 hours. To re-can, remove the lid and check the jar sealing surface for tiny nicks. Change the jar if necessary; add a new treated lid and reprocess using the same processing time.
- Product dark at top of jar
Not necessarily a sign of spoilage.
- Cloudy liquid
Sometimes denotes spoilage.
- Color changes that are undesirable
- Sediment in jars
Not necessarily a sign of spoilage.
- Spoilage
- Floating (especially some fruits)
For more on these problems, check out this page from the Clemson University Cooperative Extension Service.
Source: Extension Food Safety Specialist, Clemson University
Do You Commit Canning Sins?
Utah State University Extension has a list of "Major Canning Sins," including the following:
 Making up own canning recipe.
- Adding extra starch, flour or other thickener to recipe.
- Adding extra onions, chili, bell peppers, or other vegetables to salsas.
- Using oven instead of water bath for processing.
- Not making altitude adjustments.
- Not venting pressure cooker first.
- Not having gauge pressure canners tested annually.
- Failure to acidify canned tomatoes.
- Cooling pressure canner under running water.
- Letting food cool before processing in the recipes that call for “hot pack.”
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