Grapefruit: the citrus with the most potent scent molecule

Where does grapefruit come from?

Grapefruit, Citrus × paradisi, originated in Barbados in the 18th century as an accidental cross between the sweet orange and the pomelo, both brought to the Caribbean from Asia in the 17th century. Wikipedia's article on grapefruit notes that it was taken to Florida in 1823, and that its true hybrid origin was only established in the 1940s, when its official name became Citrus × paradisi. Perfumery uses an oil expressed from the peel.

What does grapefruit smell like?

Grapefruit smells fresh and zesty, with a faint sulfurous twist. Its most valuable aroma compound is nootkatone, a sesquiterpenoid ketone first isolated from the wood of the Alaskan yellow cedar, as the entry on nootkatone explains. The other key player is grapefruit mercaptan, the sulfur compound mainly responsible for the fruit's aroma: its racemic form is described as sulfurous, aromatic and grapefruit-like, and its R form has the lowest detection threshold ever recorded.

What does grapefruit do in a perfume?

Grapefruit belongs to the citrus family and to the citrus blend of eau de Cologne, which the history of eau de Cologne lists next to lemon, bergamot and neroli. Grapefruit mercaptan itself, or citrus oils rich in it, is sometimes used in perfumery to give a citrus effect, but its breakdown products often smell disagreeable, so the industry keeps looking for substitutes.

What should you know about grapefruit?

Expressed grapefruit oil is phototoxic. The International Fragrance Association (IFRA) Standard for expressed grapefruit oil limits it to 4.0% of the finished product in most product categories when the furocoumarin level is unknown. When it is combined with other phototoxic citrus oils such as bergamot or lemon, the use levels must be reduced so that their combined share of their respective limits stays under 100%. The class on allergens and IFRA standards explains how these limits work.