Is there a standard amount of sugar required in fruit preserves such as jams and jelly and is there a scientific way to test it. Commercial products seem to contain more sugar than fruit. Is that just for profit? I make mine with about 20% sugar or just enough to sweeten the pulp without masking the flavor. Does the low added sugar content have any negative effect on storage life? I'll be checking with the local Cornell Cooperative Extension but this forum is always quicker.