Method for treating raw materials containing collagen

A method for conditioning a collagen-containing substrate to adapt it to a subsequent hot-water extraction of collagen and collagen degradation products therefrom, said substrate being selected from the group consisting of ossein, prepared fresh, limed, and salted hides and prepared limed, dry, and salted splits, said prepared hides and splits being dehaired prior to conditioning, which method consists essentially of incubating said substrate in an aqueous bath consisting essentially of water, a neutral or alkaline protease, and urea, guanidine, or an acid addition salt of guanidine, said bath having a pH between 6.5 and 13, and then inactivating said protease when the substrate is adaptable to hot-water extraction.