Browning agents are ingredients or additives that promote browning of foods during processing, thereby imparting a darker colour to the finished product. Examples include caramel, milk and certain sugars, which supply the reactants for Maillard browning and caramelization. Commercial browning agents are often applied to foods cooked in microwave ovens, where the cooking mechanism produces little surface browning, in order to give the product an appetizing golden appearance. They must be used at levels that achieve the desired colour without introducing bitter or burnt off-flavours.