Heat is the enemy of a citrus note

Cut into an orange peel and you can smell it across the room. Those are oil glands rupturing and releasing a mixture that is mostly limonene, plus a small fraction of aldehydes and esters that carry almost all of the character.

That small fraction is fragile. Warm it and it changes.

Cold pressing — scraping or crushing the peel and separating the oil mechanically — never takes the material far above ambient temperature. What comes out is close to what was in the fruit, which is why cold-pressed citrus oil smells like the peel you just cut.

Distillation uses heat and steam. It is efficient, it produces a clean and stable oil, and it is the right process for a great many materials. For citrus it costs you the top: the delicate aldehydes are partly lost or altered, and the result is flatter and more generic — recognisably citrus, less recognisably that fruit.

Oxidation is the second half of the problem

Limonene oxidises readily once it has air, warmth and time. Oxidised citrus oil develops the characteristic stale, faintly turpentine note that anyone who has kept a bottle of orange oil too long will know. Which is why extraction is only half the story — how the oil is stored, and how quickly it goes from press to product, matters just as much.

We cold-press our own citrus oil rather than importing it, which is mostly a decision about that gap in time.