According to About.com, one of the trickiest aspects of making jam without sugar is keeping it fresh, since sugar acts as a natural preservative. To ensure that this jam doesn't spoil, store it in the freezer.
Boil the fruit
Use a blender or food processor to puree the fruit you are using for the jam. Add a splash of fruit juice if the resulting pulp is very thick. Put the pulp in a large saucepan, and cook it over medium heat until it begins to liquefy.
Add juice and thickener
Add 1/3 cup fruit juice to the jam mixture. Also add a teaspoon of no-sugar pectin to give the jam consistency. At this point, a sweetener other than sugar, such as honey, can also be added to the jam, but is not required. Stir the new ingredients into the jam and bring the mixture to a rolling boil.
Can the jam
Ladle the hot jam into glass jars, then seal the jars. Place the jars in a pot of boiling water for about 10 minutes, then remove them from the heat and allow them to cool for 24 hours. Check the seals on the jars to ensure that they are airtight before storing them.