"Gelled preserves rely on the natural acidity present in most fruits for safe food preservation. Most fruits have natural acids so resulting jams or jellies can be safely canned in a boiling water bath process. Pumpkin, however, is a low acid vegetable and cannot be safely canned in the boiling water bath process. A jam or sweetened preserve would have to have enough sugar and/or added acid to be treated safely without concerns about botulism. A certain acidity level is also required to cause the pectin molecule to form a gel structure. The USDA and Georgia Cooperative Extension currently do not have any tested recipes to recommend for safely canning pumpkin preserves (jams, jellies, conserves, or pumpkin butter) and storing them at room temperature. These pumpkin products must be stored in the refrigerator or freezer and treated the same as fresh pumpkin. Refer to National Center for Home Food Preservation | UGA Publications
for more information."