| 摘要 |
963,473. Drying in electric fields. UNILEVER Ltd. July 20, 1960 [May 21, 1959], No. 17398/59. Heading F4G. [Also in Divisions A2 and H5] A foodstuff is dried in a substantially uncompressed state by exposing it under low pressure and at a temperature above the freezing point of water to microwaves of wavelength from 3 to 50 cm., preferably from 10 to 35 cm., which are supplied at such intensity that water present in the foodstuff is rapidly vaporized therefrom, the water vapour thus generated being continuously removed. Food is dried within a glass flask 4 permeable to microwave energy and mounted on a polytetrafluoroethylene trolley 5 movable on rails 6 within a microwave oven 1 coupled to a magnetron by a waveguide 2. The neck of the flask is connected through flexible pressure tubing 8 to a rotary vacuum pump 10 by way of condensers 12, 13. During drying the trolley is moved slowly to and fro on the rails to improve the uniformity of absorption of the microwave energy and overheating of the food is avoided by the provision of flowing water through a tube 16 in the oven whereby the proportion of microwave energy absorbed by the water in the tube increases continuously as the food loses its water. |
