A method of and an apparatus for producing processed foodstuffs by passing an electric current to foodstuff materials including a container of insulating material open at opposite sides for receiving a foodstuff material suitably permeated with a salt solution which is placed in the container and held between a pair of electrode members located at the opposite open sides of the container. An annular coil is arranged around the container. As electric currents are passed simultaneously through the annular coil and between the pair of electrode members, Joule heat is generated in the foodstuff material to thermally treat and sterilize the foodstuff material while lines of magnetic force are produced and applied to the foodstuff material in such a manner that an AC magnetic field exerts influences on the electric current flowing through the foodstuff material, to render substantially uniform the temperature distribution in the foodstuff material and increase the amount of inosinic acid or glutamic acid therein.
