The punch-maker's syrup
Oleo saccharum: citrus oil and sugar
How sugar draws the oil out of citrus peel into a fragrant syrup, how to avoid the bitter pith, how to use it in punch and sours, and how to store it.
Oleo saccharum — "oil sugar" — is citrus peel buried in sugar until the sugar pulls the oil out of it and dissolves into a thick, intensely fragrant syrup. It was the base of punch for as long as punch has been made, and it does something juice cannot: it carries the peel's aroma, which is where most of a lemon's smell lives.
It is easy, needs no heat and uses peel you would otherwise throw away, which makes it the best first advanced technique for anyone who already juices citrus.
Peel without pith
Use a vegetable peeler to take wide strips of the coloured zest only. The white pith underneath is bitter and gives up that bitterness to the sugar; a strip you can almost see through is right. Unwaxed fruit is best; otherwise scrub the peel in warm water first.
Lemon is the classic. Orange, grapefruit and lime work too, and mixing them is fine.
The method
Weigh the peel and add the same weight of caster sugar. Toss or muddle them together in a bowl so every strip is coated, cover, and leave at room temperature. Within an hour the sugar starts to look wet; after several hours, and better overnight in the fridge, there is a pool of oily syrup and the peel has gone limp.
Stir and press the peel to free the last of the syrup, then strain it out. If sugar crystals remain, a splash of the punch's citrus juice or a little warm water dissolves them — and that turns the oleo into a citrus syrup you can use straight away.
- Ratio
- Equal weights of peel and sugar is the usual starting point. More sugar gives a sweeter, thicker syrup with the same aroma.
- Time
- From about an hour for a quick, light oleo to overnight for the fullest one. Longer than a day or two adds little.
Using it
In a punch, the oleo is the sugar: dissolve it in the citrus juice, then add the spirits, tea or water. A punch made this way smells of lemon in a way that one made with juice and simple syrup does not. It is also a lovely replacement for simple syrup in a Tom Collins or a Whiskey Sour, measure for measure once it is dissolved to the same sweetness.
Because it is a by-product of juicing, it is a natural companion to milk punch and to any party where a lot of citrus is being squeezed.
Storage and what goes wrong
Keep finished oleo or citrus syrup in a sealed jar in the fridge and use it within a week or two, tasting before use; discard it if it fizzes, smells of alcohol or vinegar, or grows anything. The peel's aroma is the first thing to fade.
- Bitter
- Too much pith on the peel. Peel thinner next time.
- Little syrup
- Too short, or the sugar was coarse. Muddle again and give it more time.
- Gritty
- Undissolved sugar. Dissolve it with a splash of juice or warm water.
The short version
- Equal weights of thin citrus peel and sugar, left an hour to overnight, give a fragrant syrup.
- Peel only the coloured zest; pith makes it bitter.
- Use it as the sugar in punch, or in place of simple syrup in a sour.
- Keep it in the fridge and use it within a week or two.
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What separates a syrup, a cordial, a shrub, a tincture and an oleo saccharum: what each is made in, how sweet and sour it is, how much goes in a drink and how long it keeps.