Toast is bread that has been browned by exposure to radiant heat. This browning is the result of a Maillard reaction, altering the flavor of the bread as well as making it firmer so it holds toppings more securely. Toasting is a common method of making stale bread more palatable. Bread is usually toasted using a toaster, an electrical appliance with heating elements. Toast is most commonly eaten with butter or margarine and sweetened toppings. Toast is a common breakfast food. Toast may contain carcinogens caused by the browning process.[citation needed]