Bulletin #4039, Let’s Preserve Jellies, Jams, Spreads (PDF) Adapted from Penn State College of Agricultural Sciences, Let’s Preserve Jelly, Jam, Spreads (University Park, PA: The Pennsylvania State University, 2004). For information about UMaine Extension programs and resources, visit extension.umaine.edu. Find more of our publications and books at extension.umaine.edu/publications/. General Canning Procedures To sterilize empty jars,