Described are packaged, sterile medical graft products containing controlled levels of a growth factor such as Fibroblast Growth Factor-2 (FGF-2). Also described are methods of manufacturing medical graft products wherein processing, including sterilization, is controlled and monitored to provide medical graft products having modulated, known levels of a extracellular matrix factor, such as a growth factor, e.g. FGF-2. Preferred graft materials are extracellular matrix materials isolated from human or animal donors, particularly submucosa-containing extracellular matrix materials. Further described are ECM compositions that are or are useful for preparing gels, and related methods for preparation and use.