Flash evaporation is the rapid evaporation of volatile components from a substance — fruit juice concentrate plants use it to strip water fast, and flavour houses to capture aromas. The liquid is heated under pressure, then released into a low-pressure chamber: the sudden pressure drop flashes a portion instantly to vapour, no prolonged boiling needed. The speed protects heat-sensitive flavours — the juice tastes fresher than long-boiled concentrate — and the staged chambers of a multi-effect evaporator reuse the vapour’s heat with remarkable efficiency. The same physics runs in reverse for aroma recovery: flash the volatiles off first, condense them separately, and add them back to the concentrate. It is evaporation by pressure shock rather than by patient simmering — the industrial shortcut to concentration without cooking.