charring

Charring is the partial combustion or carbonization of organic material in a limited supply of oxygen, resulting in a blackened, carbon-rich surface or residue known as char. It differs from complete combustion, where the material is fully oxidized with flames. Charring can occur unintentionally during fires or cooking, or be produced deliberately to create a protective layer or charcoal.

The process involves heating the material to temperatures where volatile compounds are driven off and the remaining substance becomes increasingly carbon-dense. In wood, a char layer forms on the surface and can insulate the underlying material, slowing further degradation during heat exposure. In food, surface charring arises from very high heat near the surface and is influenced by moisture, fat, and time; deeper charring can alter texture and flavor.

Charring has several practical contexts. In fire safety and building materials, a char layer can protect structural wood by delaying ignition and reducing heat transfer. In metallurgy, historically, charcoal supplied carbon for metal production and refining. In archaeology and paleoenvironmental studies, charred plant and animal remains provide clues about past fires, diets, and environments due to their preservation.

In cuisine, controlled charring contributes flavor and color through Maillard reactions and caramelization, but excessive charring can produce polycyclic aromatic hydrocarbons and heterocyclic amines, which carry health concerns with long-term exposure. Cooking practices often aim to balance desirable flavor with the minimization of harmful compounds.