Smelly compounds occasionally contaminate final products, and can be difficult to remove because they can be detected at very low levels. Smell and taste are some organoleptic characteristics [1]. Many are small molecules with low molecular weight, and they may be quite volatile.
Examples: thiols, smoke (some may be released by hydrolysis: wine), trichloroanisole, tribromoanisole, more. p-Methoxybenzaldehyde, a component of cherry flavoring.
“What Is Organoleptic Testing?” https://www.reference.com/health/organoleptic-testing-55fb32bb6a9a5a8a
