The invention contemplates a method for sterilizing protein or collagen-based hard and soft tissues, from animal and human donors or created synthetically by exposure to genipin, an active compound found in gardenia fruit extract. Genipin sterilizes the tissues through crosslinking the organic framework of microbes while maintaining or enhancing mechanical strength of the tissue graft by stabilizing the collagen backbone with crosslinks bone allografts experience significant and repetitive loads during their duty cycle, sterilizing bone allografts without causing a loss in biomechanical properties is quite important.