Why does the smell of burnt toast linger? © Getty Images

Why does the smell of burnt toast linger?

Burning any organic material sufficiently will produce chemicals that we are sensitive to, but why is toast so effective in broadcasting this smell?

Asked by: Anonymous

Advertisement

Burning organic material produces chemicals called polycyclic aromatic hydrocarbons (PAHs). These compounds are all quite toxic and so we have developed a high sensitivity to them.

PAHs are produced when any food is burned sufficiently, but toast tends to broadcast the smell best because it’s a dry food without any fat to trap the smoke particles. Also, it’s cooked in an open toaster or grill, rather than an oven or microwave. Smoke particles are small enough to quickly spread across the room and easily get trapped in curtain fabrics or bound to the paint on the walls.


Advertisement

Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun science facts.