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Preventing Spoilage


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Preventing Spoilage

Even though sugar helps preserve jellies and jams, molds can grow on the surface of these products. Research now indicates that the mold which people usually scrape off the surface of jellies may not be as harmless as it seems. Mycotoxins have been found in some jars of jelly having surface mold growth. Mycotoxins are known to cause cancer in animals; their effects on humans are still being researched.

Because of possible mold contamination, paraffin or wax seals are no longer recommended for any sweet spread, including jellies. To prevent growth of molds and loss of good flavor or color, fill products hot into sterile Mason jars, leaving 1/4-inch headspace, seal with self-sealing lids, and process 5 minutes in a boiling-water canner Correct process time at higher elevations by adding 1 additional minute per 1,000 ft above sea level. If unsterile jars are used, the filled jars should be processed 10 minutes. Use of sterile jars is preferred, especially when fruits are low in pectin, since the added 5-minute process time may cause weak gels. For more informations see Sterilizing of Empty Jars.



General Information

  • General Information - Jams & Jelly Products
  • Types of Jellied Products
  • Jellied Product Ingredients


  • Extracting Juice for Jelly
  • General Information on Canning Jams, Jellies, and Marmalades
  • Making Jelly without added Pectin
  • Making Jam without added Pectin
  • Making Jams and Jellies with added Pectin
  • Processing Jams and Jellies
  • Steps in Processing Jams and Jellies
  • Testing Jelly without Added Pectin
  • Remaking Soft Jellies
  • Stiff Jams or Jellies
  • Storing Home-Canned Jams and Jellies
  • Causes and Possible Solutions for Problems with Jellied Fruit Products
  • These documents were adapted from the "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA, revised 2009 &
    From "So Easy to Preserve", 5th ed. 2006. Bulletin 989, Cooperative Extension Service, The University of Georgia, Athens. Revised by Elizabeth L. Andress. Ph.D. and Judy A. Harrison, Ph.D., Extension Foods Specialists.