A bittering agent is a flavoring agent added to a food or beverage to impart a bitter taste, possibly in addition to other effects. While many substances are bitter to a greater or lesser degree, a few substances are used specifically for their bitterness, especially to balance other flavors, such as sweetness. Notable beverage examples include caffeine, found naturally in tea and coffee and added to many soft drinks, hops in beer, and quinine in tonic water.
Food examples include bitter melon, which may be mixed into a stir fry or soup for its bitter flavor.
Potent bittering agents may also be added to dangerous products as aversive agents to make them foul tasting, so as to prevent accidental poisoning. Examples including anti-freeze, household cleaning products[1] and pesticides such as slug pellets. In general dangerous products with bright colours, which may be appealing to children, often contain agents such as denatonium. However, the efficacy of using bittering agents for this purpose is not conclusive.