Cutting into a firm, heavy grapefruit early in the morning as the coffee brews is a reminder that the joy of life needs bitterness. Like all citrus oils, grapefruit essential oil is made up of a large proportion of the bright, lemony monoterpene Limonene. It is the trace compounds in grapefruit that give it the characteristic dry bitterness, particularly nootkatone.

Grapefruit (Citrus paradisi) is a hybrid of the pomelo (Citrus maxima) and the sweet orange (Citrus x sinensis). There are notable differences in the scent profile across types, from the driest white grapefruit to the juiciest ruby red. The combination of sweet, bitter, tangy, and woody makes grapefruit an ideal top note for many compositions and, moreso, for use in flavor applications, particularly beverages. However, the sulfur compounds in grapefruit oils are less stable than many perfume ingredients and can produce off odors that limit shelf life. For this reason, grapefruit oils are rarely used in commercial perfumes. Instead perfumers go to great lengths to recreate the grapefruit scent while sticking to a budget.

While citrus oils, whether expressed or distilled, and many of the naturally-derived isolates, are relatively inexpensive compared to other fine perfume ingredients, nootkatone, the characteristic grapefruit ingredient, has remained expensive. Arctander notes that distilled oils are of a much lower quality than expressed and are mainly used in low-cost “citrus oils.” It occurs naturally in grapefruit skin and in the wood of Alaska yellow cedar trees in minute levels. Biotech approaches to convert valencene derived from oranges (a similar compound) using modified oxidizing enzymes or other approaches have been successful at increasing supply, but the price remains high. Now, the EPA has registered nootkatone as an insect repellant with broad activity against mosquitoes, ticks, and other biting insects. The EPA announcement notes that nootkatone was discovered and developed as an insecticide by the Centers for Disease Control and Prevention. The large demand pull for nootkatone from insect repellant producers will ultimately lead to a large enough supply for DIY and smaller perfumers to use the compound more widely. This should lead to rapid growth of grapefruit-themed commercial perfumes.

Grapefruit oil, due to its lower cost and similarity in terms of bitterness, is used to augment bergamot in the top notes of many perfumes. Nootkatone, in addition to being the “characteristic” grapefruit scent, lasts well into the heart of most perfume compositions.

Grapefruit Aromatic Properties and Chemical Composition

Lemony: Expressed grapefruit oil is 90-95% limonene. This is the bright lemony, tangy “citrus” scent, but without any nuance of grapefruit

Terpy, Woody: At 2%, myrcene is the next largest constituent of grapefruit oil. It has the characteristic scent of terpenes, woody, herbaceous, earthy, leafy. It is the most common terpene in cannabis, which may explain the grapefruit scent in some strains of cannabis.

Pine: α-pinene (0.6%) and sabinene (0.5%) contribute a bright piney, spicy that is terpenic, but distinct from the myrcenol.

Aldehydic: Octanol (0.5%) provides the waxy, fatty, green lift that we expect from modern perfumes.