PCT No. PCT/GB98/02840 Sec. 371 Date Jul. 14, 1999 Sec. 102(e) Date Jul. 14, 1999 PCT Filed Sep. 18, 1998 PCT Pub. No. WO99/13741 PCT Pub. Date Mar. 25, 1999Food is rendered sterile by UV irradiation, preferably with UV at 265+/-15 nm. A sterilization unit may include UV sources (90, 100, 110, 120) and a heat source, which may be a broad band UV source, a source of IR or microwave radiation. A combined microwave/UV unit can be used to defrost frozen food and simultaneously sterilize it or maintain sterility. Heating prior to UV irradiation can enhance the sterilization, as can rapid cooling after irradiation. Irradiation can also be enhanced by displacing the food during irradiation e.g. by supporting it on a rotatable support (135) and/or by displacing it relative to the support surface.