Methanethiol

Methanethiol, also called methyl mercaptan, is the simplest thiol and one of the most pungent aroma compounds known, detectable by the human nose at parts-per-billion levels. In food it is a double-edged sword: at trace levels it contributes to the characteristic flavor of cheeses such as Cheddar and Camembert, but at higher concentrations it produces rotten-cabbage and sulfurous off-notes in spoiled meat, stale beer, light-struck wine, and heat-abused milk. It forms when sulfur-containing amino acids break down during microbial spoilage or thermal abuse. Because humans detect it at such low thresholds, it is a sensitive marker of protein degradation and microbial spoilage, and analysts track it with sulfur-selective detectors.