From University of California:
Jams, Jellies, and Preserves
Understanding the science behind jams, jellies and preserves is important to achieving a stable, safe, and appropriately firm product. This section has links to regulations pertaining to the production of this category of foods as well as to articles on the science behind making a high-quality jam or jelly.
Title 21 PART 150–Fruit Butters, Jellies, Preserves, and Related Products – FDA
The is the U.S. standard of identity for fruit butters, jellies, preserves, and related products. Title 21 of the Code of Federal Regulations Section 150.
The Science & Technology of Making Preserves (p. 4)
Manufacture of Low Sugar/No Sugar Jams and Jellies (p. 1)
Venture Newsletter. Cornell University New York State Agriculture Experiment Station.
Fruit Jellies – Food Processing for Entrepreneurs Series – (PDF 631 KB)
University of Nebraska Extension, Institute of Agriculture and Natural Resources