Patent GB-978806-A (GB)
Title: Method and apparatus for heating and sterilising a fluid foodstuff
IPC: A23L3/18
Filed: 1962-05-09
Abstract: 978,806. Direct contact heating of liquids. W. M. MARTIN. May 9, 1962, No. 17901/62. Heading F4K. [Also in Divisions A2, B1 and G1] A fluid foodstuff is heated and sterilized in continuous flow prior to packaging in cans, by flowing it over and in contact with a heat exchanger surface and in a thin moving body such that the exposed surface of the body of foodstuff is in direct contact with a rapidly moving body of hot gas without intermixture of the food and the gas, and all other surfaces of the foodstuff are maintained in contact with bodies at a cooler temperature. The procedure is aimed at preventing disintegration, attrition or mushing of the solid components of such foods as vegetable soup or beef stew. Fluid foodstuff consisting of a liquid component 31, Fig. 1, and blanched solid pieces metered off a conveyer belt 62 in controlled proportions by a mixer D are pumped by a pump E through inlet piping 105, 117 to be poured by a revolving spout 122, Figs. 1 and 2, rotating at between 30 and 80 r.p.m., on to the upper end of a generally conical wall 114 of a heater F to form a gently-moving film-type stream at all times covering and insulating the wall. Superheated steam or other heated gas, such as nitrogen, helium or air (when oxidation is no problem), from an inlet 128 at a temperature of between 800‹ and 1200‹ F. and at 45-50 lbs. per sq. inch gauge pressure, is impelled on to the flowing stream of food in a,rapidly whirling vortex by impeller blades 145 mounted on a shaft 134 rotating at speeds of the order 1800 r.p.m. in co-operation with fixed baffles 146 tilted in the opposite direction to that of the blades (see Fig. 1), and cooled gas at a temperature of between 350‹ and 450‹ F. is exhausted for re-heating through an outlet 149 by the blades 141 of a fan 135 also rotating with the shaft 134. A watercooled channel 129 is provided in the wall adjacent the food-gas interface so that spattered food will not be burned on to the surface. The foodstuff now heated in a matter of a few seconds to a temperature of the order of 275- 300‹ F. passes from an outlet 185 into an insulated tube 196, Fig. 1, of sufficient diameter to prevent damage to solid pieces of the foodstuff and by which it is held at the desired temperature for a time sufficient to complete the sterilization. A temperature sensing element 160 for the foodstuff at the outlet 185 regulates through a controller 161 the quantities of air and gaseous fuel constant-ratio-mixture fed through a pipe 166 to the gas burners 151 of the superheater. A flat 183, Fig. 2, in the outlet chamber 181 controls through a lever system 186, 188, 189, the needle valve 187 which throttles a constant stream of air under pressure from a pneumatic tube 190 serving as a control for the variable-speed motor H, Fig. 1, driving the pump E, conveyer 62 and the solids supply, metering and blanching unit C; the pressureequalizing tube 147 maintains the pressure in the chamber 181 at the same level as that in the chamber 132, so that the level of the float 183 is not affected by pressure differences. Pressure loss caused by constantly bleeding air from the system through orifice 156 is compensated through a pressure controller 171 by admission of live steam (or other heated gas) through an inlet 157. The gas in contact with the foodstuff should be at an elevated pressure at least equal to the vapour pressure of the gas at the temperature of sterilization in order to avoid flashing of the foodstuff, and the quantity of circulation and temperature of the steam may be high enough to evaporate some of the liquid food into steam. The apparatus may be presterilized using a flow of hot water. In an alternative embodiment, Fig. 6, steam from a superheater 421 is passed into a central manifold 411 from which a series of tubes 412 extend out radially, a nozzle 413 at the outer end of each tube imparting a whirling motion to the steam; in this case the steam is at such a relatively low temperature, e.g. 350-360‹ F., that it will mostly condense on the surface of the foodstuff. Examples relates to the heating and sterilization of green split pea slurries containing diced potatoes and carrots, cream of potato soup, cream of chicken soup, " beef-burger " soup and minestrone. Other ingredients mentioned are: celery, onions, cubes of beef and slices of ham. Specifications 978,807 and 978,808 are referred to.