Patent GB-521715-A (GB)
Title: Improvements in low-temperature processes for the preservation of perishable foodstuffs
IPC: A23L3/37
Filed: 1938-11-22
Abstract: 521,715. Freezing fish etc.; refrigerating. JOSEPHSON, sen., W. S., and JOSEPHSON, jun., W. S. Nov. 22, 1938, No. 33956. [Class 29] Compression systems.-A quick-freezing process for the preservation of fish, meat and other foodstuffs consists in subjecting them to the direct action of evaporating carbon dioxide, the vapour being continuously withdrawn, compressed and condensed and the condensate reevaporated in the freezing chamber. The fish 63 supported on a stand 61 are first drenched with water, brine or other solution and then placed in the freezing vessel 10 with a hinged cover 45 secured by swing bolts 51. Liquid CO2 from a main 11 is admitted through a regulating valve 12 and vaporises in the vessel 10, baffles 57, 58 deflecting the blast of gas to prevent mechanical damage to the foodstuffs. The gas leaves the vessel through a pipe 13 and adjustable relief valve 14 to a gas main 15. The temperature within the vessel is regulated by controlling the pressure of the spring 69 of the relief valve by a handwheel 74, a thermometer 78 and' pressure gauge 77 being provided. Gas from the main 15 passes into a receiver 9 and thence to a heat exchanger 16 where it cools liquid CO., flowing to the main 11. The gas then passes by a pipe 18 to a dessicator 27 containing silica gel, calcium choride and chips of marble to remove acid, and thence through a filter and deodoriser 21 containing activated charcoal to a compressor 23 which discharges to a filter 25 containing closelypacked particles of cellulose which remove particles of oil. The gas is liquefied in a condenser 29 and supplied through a pipe 19 to the heat exchanger 16 and main 15. When the freezing operation in any one of the vessels 10 is complete its inlet valve 12 is closed and the outlet valve 14 left open until the pressure within the vessel is the same as that in the main 15, when the valve 14 is closed. A valve 31 is then opened to vent the remaining gas to a main 33 which leads through a heat exchanger 29a to a gas holder 34 which may be counterbalanced to maintain atmospheric pressure in the main 33, so that when the vessel 10 is opened for removal of the footstuffs the loss of gas is negligible. The liquid cooled in the heat exchanger 29a is used in the cooler 29 for liquefying the CO2. A booster pump 36 takes gas from the gas-holder 34, raises its pressure to that of the main 15 and discharges it to the heat exchanger 16 and thence to the intake side of the compressor. A steam engine 38 driving the booster pump is controlled automatically in accordance with the volume of gas in the gasholder by a slotted lever 39 engaging a pin 41 on the gas holder and operating the steam valve. The stand 61 for the foodstuffs comprises a base 60 with holes 80 for the passage of gas and a series of platforms 62. A modified freezing vessel is open at the bottom and the goods are placed on a platform constituting the head of an hydraulic press adapted to close the vessel ; in this form the baffles comprise plates accommodated in a pocket in the wall of the vessel.