Definition
Molecular distillation, also called short-path distillation, is a separation process run under high vacuum, at pressures below 0.001 mbar. It isolates or fractionates natural extracts at temperatures 50 to 100 °C lower than classical distillation, preserving heat-sensitive aromatic molecules.
Origin and history
The process was developed in the 1930s and 1940s by American engineer Kenneth Hickman for the vitamins and fine oils industry (source: Wikipedia). Perfumery adopted it from the 1950s and 1960s, to purify natural essences at low temperature. The principle: a very short path between evaporator and condenser under high vacuum, where molecules vaporize at low temperature and deposit on the cold surface opposite (source: ScienceDirect).
Use in perfumery
Molecular distillation yields natural extracts of high purity or targeted fractions: concentration of vetiveryl acetates from vetiver heartwood, isolation of santalol fractions from sandalwood, refinement of ambergris fractions (source: Perfumer & Flavorist). Givaudan, Firmenich and Robertet use it for their premium naturals. The lower temperature and short exposure time deliver purer extracts than classical distillation. The process remains contested by advocates of the traditional alembic, who see it as an industrial shortcut.