A method is disclosed which inactivates protease enzyme in fish, such as arrowtooth flounder, having this enzyme in a portion thereof. In the process, the fish are minced and then subsequently mixed with a starchy and/or proteinaceous material to form a mixture which is then subjected to high-temperature, short-time processing in a screw extruder containing a reaction zone. The present invention also relates to a method for proteolytic degradation of fish muscle having protease enzyme which includes distributing the enzyme uniformly throughout the fish muscle and drying the fish muscle thereafter. The present invention also relates to a method of making a food product and includes reducing hydrolyzed fish muscle to a powdered form, and then mixing the fish muscle in powder form with a starchy and/or proteinaceous material to form a mixture which is subsequently subjected to high temperature extrusion processing to form a desired food product. The present invention further relates to processes for tenderizing or causing substantial or complete proteolytic degradation of animal muscle by applying onto the animal muscle, protease enzyme obtained from fish having the enzyme present therein. Also disclosed is the resulting food products resulting from these processes.