Citrus oils are not distilled. They are pressed. The difference explains why bergamot, lemon, and grapefruit smell the way they do — and why they disappear so fast.
Cold pressing — also called expression or cold expression — is the extraction method used for citrus essential oils.
The oil is contained in the peel (the flavedo) of the fruit, not in the juice or pulp. In industrial production, the whole fruit or the rind is mechanically pressed or rasped in equipment that ruptures the oil-containing glands.
The oil is released, combined with water from the fruit, and then separated by centrifugation. No heat is applied.
This matters: the aromatic molecules in citrus peel are monoterpenes — primarily limonene, linalool, pinene — that are highly volatile and heat-sensitive. Steam distillation would alter or destroy them. Cold pressing preserves the aromatic profile intact, which is why cold-pressed bergamot, lemon, and grapefruit oils smell like the fresh peel of the fruit. It is also why these oils are the most volatile in a formula — they were never cooked into stability.

FACTS
Groom (The Perfume Handbook) documents cold expression as the definitive citrus extraction method, noting that bergamot oil from Calabria was historically produced by hand (using a sponge pressed against the rind over a collection vessel) before industrial mechanisation.
RSC Chemistry of Fragrances identifies limonene as the dominant aromatic compound in most citrus peels — it constitutes approximately 90-95% of lemon oil and 80% of bergamot oil by weight — and confirms its extreme volatility: it is the compound primarily responsible for the immediate brightness of citrus top notes and their rapid evaporation.
Piesse (The Art of Perfumery, 1879) distinguishes between pressed citrus oils and those obtained by distillation, noting that distillation yields an inferior, terpene-heavy product lacking the delicacy of cold-expressed oils.
TAKEAWAY
Cold-pressed citrus oils are Act 1 materials. Their volatility is not a flaw — it is the result of their extraction method preserving their most volatile compounds intact. This is why a bergamot, lemon, or neroli top note opens so cleanly and fades so quickly.
If you want citrus presence in Act 2 or beyond, you need to construct it with citrus-character synthetics (citronellal, citral derivatives) that have lower volatility. The cold-pressed oil is the opening. It is not meant to last.