Mold growth in foods can raise the pH of the food. In home canned products, this could mean that the high acid products could become low acid and therefore run the risk of botulism or other bacterial spoilage. Thus, any home canned product that shows signs of mold growth should be discarded. USDA and microbiologists now recommend against even scooping out the mold on jams and jelly products and using the remaining jam or jelly, even though that used to be suggested.
It is best to follow guidelines set out by So Easy to Preserve, University of Georgia Cooperative Extension Service, and other reliable sources such as Missouri Families or the National Center for Home Food Preservation.
Contributor: Maude Harris, EdD, Nutrition and Health Education Specialist, University of Missouri Extention, firstname.lastname@example.org