Harvesting Bergamot: Picking for Peel Oil, Paring the Flavedo and the Burn Risk

Read this before you cut a bergamot open

Bergamot peel oil is strongly phototoxic, and this is not a cautious footnote. The oil contains furocoumarins that do nothing at all on their own but react violently under ultraviolet light. Juice, zest or oil left on skin that is then exposed to sunlight produces a delayed chemical burn, typically appearing many hours later as redness, then as blistering that can be severe, followed by dark brown staining that persists for months and sometimes for more than a year. The pattern is unmistakable when it happens, usually running in drips and streaks down a forearm or as handprints where somebody held the fruit.

The practical rules are simple and you should follow all of them. Handle and process the fruit indoors or in shade, never sitting out in the sun with a bowl of peel. Wear gloves whenever you are cutting, juicing or paring, and keep the oil off your forearms as well as your hands. Wash thoroughly with soap and warm water immediately afterwards, since plain water does not shift an oil. And keep skin that has touched the fruit out of direct sun for at least the rest of the day, and preferably for a full day and night.

Take particular care with children who want to help, with anybody handling the fruit outdoors on a bright day, and with the fruit that a curious visitor picks up and squeezes. The delay between exposure and reaction is what catches people out: nothing hurts at the time, so nobody thinks to wash, and the burn appears that evening or the following morning long after the connection has been forgotten. None of this makes the fruit unsafe to use in a kitchen. It makes it a fruit you process deliberately, in shade, with gloves on.

The same chemistry is the reason bergamot oil is regulated in perfumery and why some products use a version with the furocoumarins removed. Home pared peel and home pressed oil are the full strength original. Treat what you produce accordingly, and do not apply it to skin.

The crop is the peel, and the fruit is not for eating

Everything about harvesting this species follows from one fact: the valuable part is the thin colored outer layer of the rind, called the flavedo, which is studded with oil glands you can see as pinpricks when you hold the peel to the light. The flesh is very sour, harshly bitter and sharply acidic, well beyond a lemon, and nobody eats it fresh. Judging ripeness by taste, the habit you carry over from every other fruit in the garden, tells you nothing useful here.

Judge by the rind instead. A bergamot ready to pick has turned from deep green through a pale yellow green to a clear yellow, feels heavy for its size, and gives a sharp bright burst of scent when you scratch the surface with a fingernail. That scratch test is the single most useful check you have, because oil content in the flavedo peaks as the fruit finishes coloring and falls away again if it hangs too long. Fruit left on the tree past its peak looks perfectly good and yields noticeably less aroma.

The juice is worth taking even though the fruit is inedible raw. Heavily diluted and sweetened, or used a spoonful at a time as an acidulant in a marinade, dressing or preserve, it has a floral character no lemon possesses. But it is a secondary product. If you have to choose between damaging the peel to extract juice cleanly and taking the peel intact, take the peel. That is what you grew the tree for.

Cutting the fruit and paring the flavedo

Cut fruit from the branch with sharp snips rather than pulling it. The rind is thick and firmly attached, and a straight pull tears out a plug of peel at the stalk end or strips bark from the fruiting spur. Leave a stub of stalk no longer than a quarter inch (5 mm), because a longer stalk punctures the fruit lying next to it in the basket and turns a clean crop into a moldy one within a week. Pick in the morning once dew has dried, into a shallow basket rather than a deep one, and remember the thorns, which will pierce a fruit on its way past and will certainly pierce a forearm reaching into the canopy.

Paring is the skill that matters. The oil sits in the flavedo, a layer only about a sixteenth of an inch (1 to 2 mm) thick, and directly beneath it is the white pith, which is thick on this species, bitter in the wrong way and holds no aroma at all. Any pith you take with the peel dilutes and spoils the result. Work with a sharp swivel peeler or a small very sharp knife and take strips that are almost translucent, showing yellow through with only the faintest hint of white on the reverse. If the strip is opaque and spongy on the underside, you have gone too deep.

Wash the fruit only if it needs it, and dry it completely before paring. Surface oils and natural wax are part of what you are harvesting, and scrubbing removes them. Pare the fruit whole and unopened first, then cut and juice what is left, in that order, because a cut and leaking fruit is slippery, awkward to hold and much harder to pare cleanly.

1. Set up in shade with gloves on Work indoors or in full shade, never in sun. Put on gloves before the first cut and keep a bowl of warm soapy water within reach for hands, tools and the board.
2. Wipe the fruit dry and check it Dry any dampness with a cloth and set aside anything punctured or soft for immediate use. Damp peel does not dry properly afterwards and moisture carried into storage becomes mold.
3. Pare the flavedo in long strips Hold the fruit firmly and take strips from top to bottom with a swivel peeler, turning the fruit as you go. Aim for a strip that is barely opaque; a hint of white on the back is fine, a spongy layer is not.
4. Scrape back anything too thick Lay a thick strip flat with the pith facing up and scrape the white away with the flat of a small knife. This rescues heavy strips and is faster than repeating the paring.
5. Juice the pared fruit last Halve and press the pared fruit for juice, straining out seeds. Keep juicing separate from paring so that oil from squeezed peel does not coat everything you are still handling.
6. Wash everything and yourself Wash hands, forearms, board, knife and peeler with hot soapy water before doing anything else. Then keep any exposed skin out of direct sun for the rest of the day.

Keeping the peel, the oil and the juice

Whole fruit keeps a week or two in a cool room and three to four weeks refrigerated, provided it is dry, unbruised and the fruit are not touching. It does not improve in storage, and oil content only falls, so the sensible plan is to pare within a few days of picking and store the product rather than the fruit. Check anything you are holding weekly and remove soft fruit immediately, since one rotting bergamot spoils its neighbors quickly.

Dried peel is the most useful form for a home grower. Spread the pared strips in a single layer on a rack somewhere warm, dry and airy out of direct sunlight, and turn them daily until they snap cleanly instead of bending, which usually takes three to seven days depending on humidity. Stored in a sealed jar in the dark they hold their aroma for six months or more. Peel dried in sunlight loses a great deal of its character, so keep it shaded.

For a stronger and more versatile product, steep the fresh pared strips. Packed into a jar with a neutral high proof spirit and left in a dark cupboard for two to four weeks, shaken occasionally, they yield an intensely aromatic infusion that is the practical home equivalent of the oil. Packed with sugar instead, in a sealed jar for a few days, the peel draws out a fragrant syrup. Juice freezes well in small portions and loses very little, which suits an ingredient used a spoonful at a time. In every case, label the jar clearly, including the note that the contents are phototoxic and are not for use on skin.

What to record at harvest

Write down the date the first fruit turned clear yellow, the date you picked, the number and total weight taken, and the weight of pared peel it produced. That last ratio is the number that tells you whether you are paring too thickly, and comparing it across two or three seasons is far more informative than any advice, because it measures your own technique against your own fruit.

Note also which side of the tree the best fruit came from and how much sun that side gets, whether any fruit showed thorn punctures and where in the canopy those branches sat, and how long the dried peel held its scent in storage. The thorn note in particular feeds straight into your winter pruning, since it tells you exactly which congested branches to thin.