An electric cooker for the direct heating of food by the passage of alternating current therethrough has a two-way electronic valve, triggered at the beginning of each half-cycle of its power supply, connected in series therewith. A control voltage derived from a series resistor, varying with the magnitude of the load current, blocks the trigger circuit of the valve during halfcycles of a given polarity whenever the current exceeds a predetermined threshold, the trigger circuit being unswitchable during half-cycles of the opposite polarity so that only complete cycles are suppressed in the case of overload.