Cuminaldehyde
The chief aroma molecule of cumin, responsible for its earthy, warm, slightly sour smell.
Also: cumin aroma compound, cuminal, p-isopropylbenzaldehyde
Cuminaldehyde is the main component of cumin seed oil, up to about a third of its volatile content. It smells earthy, spicy and slightly green, and with related compounds such as gamma-terpinene and p-cymene gives cumin its character. When cumin is toasted, new roasted notes develop from other compounds, but cuminaldehyde remains the signature. Because it is volatile, ground cumin loses its aroma faster than whole seed. The same compound is present in smaller amounts in cassia and eucalyptus oil. Sensory chemists use it as a marker to judge cumin quality and detect adulteration in trade.