Sweet spreads with even a small amount of mold should be discarded because the visible mold is like the tip of an iceberg. There may be mold that cannot be seen growing throughout the jar. Discard any sweet spread containing mold without tasting or sniffing it. Food chemistry . Jams, jellies, marmalades, fruit butters and other sweet spreads don't spoil because of their very high sugar content.
Sugar binds up the liquid in the product, making it difficult for bacteria to grow.
Yeast and mold can grow on sweet spreads, though. Some molds that grow on jellies produce aflo-toxins, which can be toxic, especially to those with mold allergies. Some aflotoxins are also carcinogens. Benefits of processing . The recommended procedure is to pour hot sweet spreads into jars that have been sterilized by boiling for 15 minutes before filling, leaving -inch head space.