A bergamot fruit weighs about two hundred grams. Two hundred kilograms of such fruit, run through a pressing line in Reggio Calabria, give about one kilogram of greenish yellow oil. This piece follows that peel from oil gland to bottle, and explains why a small word on the label, FCF, matters so much.
Oil glands in the peel
The coloured layer of a citrus fruit is not a flat surface. Just below it sit thousands of small, rounded glands, each holding a drop of oil. When a strip of lime peel is folded, the fine spray that leaves its smell on the fingers is oil from these glands. No heat and no solvent are needed: the gland wall only has to break.
The standard ISO 9235:2021 calls this product a cold pressed essential oil, entry 3.5, and limits the definition to the outer peel of citrus fruit. No other raw material is made this way within the ISO vocabulary. Rose, lavender and sandalwood all need distillation or a solvent. Only citrus peel holds its oil close enough to the surface for mechanical force to reach it.
The volatile part of peel oil is mostly monoterpenes, led by limonene. The character of each fruit, though, sits in smaller fractions: citral in lime and lemon, linalyl acetate in bergamot. In bergamot, linalyl acetate can make up 17 to 40 percent, and this ester gives bergamot its sour, faintly floral smell, quite unlike sweet orange.
The press and the wash water
Before the machine came the hand. In Calabria and Sicily, the fruit was halved and emptied, and the half peel was pressed against a sponge; the sponge soaked up the oil and was wrung out into a vessel. In southern France there was the écuelle à piquer, a bowl lined with spikes. The fruit rolled in the bowl, the spikes pierced the glands, and the oil ran down to a tube at the centre of the base.
In 1844, in the Bourbon kingdom of southern Italy, Nicola Barilla and Luigi Autieri won a mechanisation contest with a peel rasping machine, later known as the Calabrian machine; Domenico Carbone improved it in 1875. Two main machine types grew from there. The sfumatrice works on emptied half peels: the peel is folded and squeezed between rollers, and the glands burst under their own pressure. The pelatrice works on whole fruit: abrasive rollers rasp the outer peel under jets of water.
Water is the part rarely mentioned. Oil freed from the glands is carried off by the sprays, forming a cloudy emulsion of oil in water. The emulsion then goes through a centrifuge that separates the oil layer. FAO notes that one tonne of oranges gives about 200 to 300 litres of emulsion and finally only about 3 to 6 litres of oil. In the Americas, peel oil is mostly a by-product of the juice industry: FMC extractors take juice and peel oil on the same line.
Bergamot has rules of its own. The name Bergamotto di Reggio Calabria, olio essenziale has been protected as a DOP in the European Union since 2001, and the specification requires cold extraction and separation by centrifuge, with a yield of 350 to 750 grams of oil per 100 kilograms of fruit. The fruit is picked from November to March.
Pressed and distilled: two limes
The same fruit can give two oils with two smells. Lime, Citrus aurantifolia, is the clearest case. Pressed lime oil comes from the peel and keeps citral and the smell of freshly cut rind, green and slightly bitter. Distilled lime oil, made mainly in Mexico, takes another route: the fruit is crushed, and the mix of juice and oil is steam distilled for several hours.
During those hours, the acid in the juice changes the oil. Citral falls sharply. Terpene alcohols such as alpha terpineol rise, together with a few unusual constituents such as 1,4-cineole and terpinen-1-ol. The result is a lime that smells sharper and drier, without the fresh note of the rind. Distilled lime is made in far larger volumes than pressed lime, and most of it goes into food flavouring.
Distillation does something else the nose does not notice: it leaves the non-volatile part behind. Heavy molecules do not travel with the steam into the condenser. This is why distilled lime oil is not phototoxic, although some Mexican samples have been recorded with traces of furocoumarins. Lemon exists in the same two parallel forms. Two oils, one fruit, two different safety rules.
Furocoumarins and bergapten
Pressed oil carries everything that was in the gland, including things with no smell at all. In bergamot, about 4 to 7 percent of the oil by weight is non-volatile: waxes, carotenoid pigments, coumarins and furocoumarins. Among the last group, the two most often named are bergamottin and bergapten.
Bergapten, chemically 5-methoxypsoralen, is a small molecule with the formula C12H8O4 and almost no odour value. It matters for another reason: when skin carrying bergapten meets UV light, a phototoxic reaction can follow, from redness to blistering, and can leave long lasting marks known as berloque dermatitis. Measured bergapten content varies by fruit: about 0.17 to 0.33 percent in pressed lime, 0.11 to 0.33 percent in bergamot, and far lower in lemon and grapefruit.
This is why pressed citrus oils have their own rules. The IFRA Standard for citrus oils and other furocoumarin containing essential oils sets a limit on total furocoumarins, expressed as bergapten, of 0.0015 percent, or 15 ppm, in the finished product left on sun exposed skin. For pressed bergamot, this corresponds to about 0.4 percent oil in the product. The limit does not apply to rinse off products such as soap, and when several furocoumarin containing materials are present, their amounts are added together.
In the European Union, Annex II of the Cosmetics Regulation 1223/2009 bans furocoumarins except for the amounts naturally present in essential oils; in sunscreen and tanning products, total furocoumarins must stay below 1 mg per kilogram. These figures are why a bottle of pressed bergamot always carries the instruction to avoid sun or UV light for about 12 hours after use on skin. A botanical origin does not make a molecule any less phototoxic.
Bergamot FCF
Perfumery wants the smell of bergamot without the bergapten. The answer is to separate the non-volatile part from the pressed oil. The most common method is vacuum distillation: at low pressure, the scented fraction evaporates at a moderate temperature while the heavy furocoumarins stay behind. Some producers use adsorptive filtration or an alkaline process. The product is labelled FCF, furocoumarin free, or bergaptene free.
The effect is easy to measure. In bergamot FCF, residual bergapten sits between 0 and about 0.009 percent, against 0.11 to 0.33 percent in pressed oil. As a result, the maximum skin level for FCF, based on the SCCNFP threshold, reaches 16.6 percent, while pressed bergamot stops at 0.4 percent. Because it is no longer phototoxic, FCF is widely used in cologne style perfumes, where a citrus smell is wanted without a warning about the sun.
There is a small cost. The library records bergamot FCF as lighter in smell than traditional pressed oil, with part of its signature character lost along with the furocoumarins. Smelled on two blotters side by side, the pressed oil often reads rounder and fuller, the FCF straighter and brighter. The main constituents stay the same: limonene, linalyl acetate, linalool. Only the ground beneath them has changed.
Pressed peel and shelf life
Limonene is a molecule that changes easily. Exposed to oxygen and light, it slowly turns into oxidation products, and it is these products, not fresh limonene, that can sensitise skin. Pressed peel oils therefore have a shorter life than many other essential oils. The smell shifts too: the note of freshly cut rind slowly flattens.
Storage is therefore simple and strict: dark glass, a tight cap, as little air space as possible, a cool place or a refrigerator. Producers often add an antioxidant to formulas containing citrus oil. At Lê Mai, each bottle of peel oil carries a lot number, because with an oil built on limonene, time is part of the composition.
On the label, a few words say a lot. Expressed, cold pressed or CP means pressed oil. Distilled means distilled oil. FCF or bergaptene free means the furocoumarins have been removed. Terpeneless, or figures such as 5x and 10x, means the oil has been concentrated by removing part of the limonene. A region, Calabria or Mexico, is named because the same fruit grown in two places gives two different compositions. The story of sunlight and citrus peel continues in Lime Peel and Sunlight.
A gland breaks, and everything inside comes out together.
Distillation selects. Pressing does not.
The letters FCF on a label are the trace of that choice.