An electric toaster in which light from a light source 44 is directed onto an item to be cooked (not shown) by means of a first light guide 39. After reflection from the item, the reflected light passes down a light guide 38 to a light detector (not shown) atthe bottom of the guide. A further light detector (not shown), which acts as a reference is positioned to receive light direct from the light source and an electronic control circuit (not shown ) containing the two light detectors is used to automatically inhibit the supply of current to the heating element 6 when cooking is judged to be complete.