A method of pasteurizing or sterilizing foodstuffs utilizing microwaves, and an oven for the implementation of such a method

摘要

Foodstuff packaged in a material transparent to microwaves is conveyed continuously through an environment pressurized to 2.5 bar max so as to prevent the containers or wrappers bursting or being forced out of shape; in four steps, the temperature is raised quickly to a prescribed treatment value with high frequency microwave radiation, stabilized by applying a combination of lower power microwaves and hot air, held steady with hot air only, and then lowered by cooling. In a split-level cylindrical oven, the upper level consists in a pressure-and-temperature compensating chamber (4), a high speed heat chamber (5) with closely spaced microwave generators (24) ordered in longitudinal rows along its top and sides, the waveguides (24′, 25) of which are directed at the containers or wrappers (C) of of foodstuff from above and beneath as they are indexed through on special pallets (S), and a stabilization cham­ber (5′) in which lower power microwaves combine with air drawn through heaters (20) and circulated by a fan (21) located at the closed end of the oven; the same air is used to heat a vertical chamber (6), through which the pallets descend on an elevator (D) before passing into a cooling chamber (7) on the lower level and proceeding toward the final outgoing compensating chamber (8). Once out of the oven, the pallets (S) are raised by a further elevator (A) to the upper level for emptying and reloading.