METHOD AND APPARATUS FOR ASEPTICALLY PROCESSING A FOOD PRODUCT

Abstract: A method and apparatus are disclosed for continuously and gently aseptically processing a food product comprising delicate food chunks of fruit, vegetables or the like immersed in a liquid. The apparatus comprises a conveyor (28) for feeding food chunks (12) and a supply tube (36) for supplying liquid into a mixing hopper (32) and thence into a helical feed pump (44). An aseptic gas is also fed into the pump (44). As the food product and gas move through the helical pump the food is heated in a heating enclosure (68) to render it aseptic and then discharged into a separator (92) where the food and gas are separated.

Description: This invention relates generally to food processing, and more specifically to a method and apparatus for continuously and gently aseptically processing a food product of the type comprising delicate food chunks of fruit, or vegetables or the like immersed in a liquid. This application is related to our European Patent Application number 87301880.8, filed on 4th March 1987. A food treating device with a helical pumping system is disclosed in U.S. patent Nos. 3,489,074 and 3,586,510 which issued to D.F. Farkas et al . on January 13, 1970 and June 22, 1971, respectively. In U.S. Patent No. 3,489,074, the food treatment device comprises a helical feed pump formed from a continuous coil of tubing, and a treatment chamber for receiving the food from the feed pump and conveying it by means of a cleated belt into the inlet of a helical discharge pump, also formed from a continuous coil of tubing. U.S. Patent No. 3,586,510 discloses a food treatment device comprising a single continuous helical pump formed from a continuous coil of tubing wound on a drum and having a feed section, a holding section and a discharge section. In both devices, a slug of food material having a volume of 1/2 turn is fed into the feed pump for each revolution of the helical pump. One problem encountered by the known food treatment devices is that food product can only be fed into the helical feed pump for 1/2 turn of the pump resulting in a maximum input ratio of food product to gas of 1 to 1. This seriously limits the rate of throughput of food product achieved by the food processing device resulting in reduced efficiency of food processing. Also, such known food treatment devices further suffer from the problem of transient conditions resulting, for example, from minor variations in the rate of liquid and food product being fed into the feed pump, and the trapping of bubbles of gas in the liquid entering the feed pump. These transients will cause instability of operation resulting, among other things, in a reduced throughput of food product, and an increased exposure time of food product, on the dry inner tube wall surface resulting in product "burn on", forming a residue on the inner tube wall surface. The residue deleteriously affects the quality of the food product, the efficiency of the apparatus, and greatly increases "down time" required to clean the feed pump. Still further, prior art processing methods and apparatus while providing effective sterilization, do so by heating the food products in an inefficient manner whereby the heat up and cool down time periods are longer than desirable and the quality, e.g., the texture and taste of the food product, is diminished. In addition, prior art processing apparatus such as a scraped surface heat exchanger undesirably damages the food product during processing and therefore can often only be used for foods where the damage is hidden, such as chili, chowder and the like, where the appearance of the food particles is not critically important. Other food products such as fruit and vegetable chunks cannot tolerate such damage and when processed in accordance with the prior art produce undesirably high amounts of unacceptable product. Finally, systems described by known food treatment devices have no provision to ensure sterilization of the gas used in the process. Since heat transfer into the gas is relatively poor compared to the food product, the gas fails to reach sterilization temperature. In accordance with a preferred embodiment of the invention, a method and apparatus are disclosed for continuously and gently aseptically processing a food product comprising food chunks of delicate fruit, vegetables or the like immersed in a liquid, without damaging the delicate food chunks. In this preferred embodiment of the invention, aseptic processing is achieved by feeding a continuous uninterrupted stream of food product in a desired chunk-liquid ratio and a gas into the inlet of a rotatable helical feed pump. The feed pump is rotatably mounted in an enclosure in which the food product and gas are heated to a sterilization temperature and preferably maintained at the sterilization temperature for a time sufficient to sterilize the food product. In those situations in which the food product is not maintained at the sterilization temperature within the enclosure for a time sufficient to sterilize the food product, such sterilization must occur during the time required for passage of the food product from the enclosure into any suitable receptacle, including any time spent in the receptacle prior to cooling the product. The food product and gas are fed from the enclosure into a separator which separates the gas from the food product. The food product free of gas can be fed into any suitable receptacle, such as a hot fill bag, for example. In the known hot fill bag process, the bag is filled with food product, heat sealed and cooled by water spray or the like. In a more specific aspect of the invention, the sterile gas and liquid separator comprises a separator enclosure having an inlet and outlet, a vent in the separator enclosure, and a food product guideway mounted within the separator enclosure for connecting the separator inlet to the separator outlet, the guideway comprising a plurality of parallel spaced apart wires. A primary advantage or object of this invention is to solve the shortcomings or problems set forth in relation to prior known food treating devices. Specifically, the method and apparatus of this invention retains the flavor and texture of the product by heating the product rapidly to a sterilization temperature, and holding the product at the temperature only long enough to sterilize it. This object is achieved by, among other things, continuously feeding a food product comprising delicate food chunks of fruit, vegetable or the like immersed in a liquid in a predetermined ratio of food chunks to liquid directly into a helical feed pump. This object is further achieved by providing the helical feed pump with a gas accumulator at the inlet thereof to allow the continuous introduction of gas into the feed pump during operation of the processing apparatus. Another contributing factor to solving the problems posed by prior known treatment devices is maintaining enclosures and separators at a positive pressure to prevent non-sterile air or the like from entering therein through possible pin-hole leaks or the like in the outer walls thereof. The invention is defined in the appended claims. The invention and its advantages will become more apparent from the detailed description of the invention presented below with reference to the accompanying drawings, in which:- FIGURE 1 is a side elevation of an apparatus embodying this invention, for aseptically processing a food product; FIGURE 2 is an enlarged side elevational view of the heating enclosure and helical feed pump of the apparatus of Figure 1 with portions thereof broken away and sectioned; FIGURE 3 is a section view taken substantially along line 4-4 of Figure 2 showing the inlet end of the helical feed pump, and the food product and gas interface in the first coil of the pump, if it were transparent; FIGURE 4A is an enlarged section view of the portion of Figure 3 showing the gas accumulator, inlet pipe and gas pipe; FIGURE 4B is an enlarged side elevation view partially in section of the gas accumulator of Figure 1 showing the food product guiding device; FIGURES 5-9 are end views of the first coil of the first helical feed pump showing the gas and food product interface at various angles of rotation of the feed pump; FIGURE 10 is an enlarged section view of the first separator of the apparatus of Figure 1; FIGURE 10A is a section view taken substantially along line 10A-10A of Figure 10. Referring now to Figure 1 of the drawings, a preferred embodiment of the apparatus of this invention is shown for continuously and gently aseptically processing a food product 10. The food product comprises, for example, food chunks 12 of fruit, vegetables or the like, such as peaches, pineapple or potatoes, immersed in any suitable compatible liquid, such as, for example, fruit juice, vegetable juice or water. One Preferred embodiment of the aseptic food product processing apparatus, as best shown in Figure 1, essentially comprises means 14 for feeding the food product 10 and a first nonsterile gas into a food product heating means 16 which heats the food product to a sterilization temperature of around 100°C and holds the food product at the sterilization temperature for a sufficient time to sterilize the food product. The heated food product 10 and first gas are fed into a first separator means 18 which separates the nonsterile gas from food product 10. The food product 10, mainly devoid of gas and at its sterilization temperature or higher, is fed by gravity from separator discharge end 98 through a food product diverting valve 104 and a feed tube 106 into any suitable receptacle such as a hot-fill bag or the like while the food product remains at or above the sterilization temperature for a time sufficient to complete the sterilization of the food product before the hot fillbags cool to a substerilization temperature by convection, or are cooled by a water spray or any other suitable cooling means. The food product feeding means 14 essentially comprises a conveyor 28 or the like for feeding food chunks 12 from a supply container 30 into any suitable mixing tank or hopper 32 in a controlled manner. A liquid is also supplied from a supply container 34 through a supply tube 36, preferably in spray form or alternately in a tangential flow, into mixing hopper 32 to form the food product 10. The ratio in volume of food chunks 12 to liquid is controlled by any suitable means, such as a variable liquid control valve 38 or by speed control of conveyor 28, for example. A volumetric food product ratio of food chunks to liquid found to be suitable in the practice of this invention is 1-to-1, although other ratios of food chunks to liquid can be used. The mixing hopper 32 has a lower level switch LS-1 electrically connected to any suitable level detector and alarm to indicate to the operator when the food product level is too low. A similar upper level switch, not shown, may be provided to indicate when the food product level is too high. With reference to Figures 2 and 4B, the food product 10 is fed via feed tube 40 into inlet pipe 42 of a rotatable helical feed pump 44 of the food product heating means 16 upon opening a food product feed valve 46 in tube 40. A first suitable non-aseptic gas, such as air or nitrogen, is also fed from a pressurized gas source, not shown, into helical feed pump 44 by a small diameter pipe 48 extending through an elbow of tube 40 into and through the center of inlet pipe 42. The helical feed pump 44 comprises a generally cylindrical body 180 with a removable domed end cap 182 rotatable in end supports 186. A feed pump end support 184 supports the feed pump's components on removal of the end cap 182. The pump 44, end cap 182 and pipes 42, 48 are all coaxial. The food product and gas flow into a gas accumulator 56 which is cylindrical and has its axis radially offset from the axis of the feed pump. The food product is guided from the end of pipe 42 into a radially extending inlet leg 58 connected to the accumulator 56 by a guiding device 49 comprising a plurality of parallel, spaced apart wires or rods 51. The rods are held in a circular rigid configuration by securing the ends of the rods to openings in walls 55, 56 and to the end of inlet leg 58 of first coil 52 by any suitable means, such as welding, for example. The openings in walls 55, 56 are in alginment with the end of pipe 42 and inlet leg 58 respectively. Wall 55 forms a flange connected to a flange 57 at one end of pipe 42, and wall 56 is connected to one end of inlet leg 58. The feed pump 44 may be rotated in any known manner, e.g. by means of one or more belts (not shown) engaging belt pulley grooves 120 and/or 128. With reference to Figures 3-9, the purpose for introducing a gas into the inlet of helical feed pump 44 is to provide an upper space 50 in each coil 52 of pump 44 of a density substantially less than the density of the food product 10. By virtue of this difference in density, the food product 10 is transported at a controlled rate through coils 52 upon rotation of helical feed pump 44. Since the helical feed pump 44 per se is not new, and the theory and operation thereof is described in detail in U.S. Patent Nos. 3,489,074 and 3,586,510, and no further description in regard to the known elements thereof is believed necessary. The outlet 54 of gas pipe 48 in gas accumulator 56 has an axis that is coaxial with the common axis of pipes 42, 48 as best seen in Figures 4A and 4B. The purpose of gas accumulator 56 is to allow continuous introduction of gas into helical feed pump 44. For most efficient operation, gas accumulator 56 is positioned at an angle relative to inlet leg 58 so that a line extending through the axes of tube 42 and gas accumulator 56 forms an angle of about 45° with inlet leg 58. With first coil 52 in the positions shown in Figures 4 and 5, gas continuously introduced into pipe 48 enters accumulator 56 and passes through the food product 10 in the upwardly positioned inlet leg 58 into upper space 50 of the coil. As feed pump 44 rotates further through the positions shown in Figures 6, 7 and 8, inlet leg 58 moves downwardly and is completely filled with food product 10 effectively preventing the less dense gas from passing therethrough, the gas instead rising and filling an upper space 59 within the accumulator instead of backing up into inlet pipe 42 and interfering with the continuous flow of food product 10 into the inlet pipe. When feed pump 44 rotates further to the position shown in Figure 9, in which inlet leg 58 is inclined upwardly, the pressurized gas which is fed to accumulator 56 forces its way through food product 10 into inner leg 58 to form a gas pocket 60 at the upper end of inlet leg 58. For the remainder of such cycle of rotation, inlet leg 58 is positioned upwardly and the lighter gas passes therethrough into the upper coil space 50, as seen in Figures 4 and 5. The continuous flow of gas into gas accumulator 56 through each cycle of operation is necessary to achieve a gas filled space whose volume, density and specific gravity can be more consistently controlled. It has been found that by properly controlling the continuous gas flow along with the continuous flow of food product 10 to achieve a volumetric ratio of food product to gas of about five to one, a satisfactory and controlled rate of food product transport through helical feed pump 44 can be achieved. The inlet pipe 42 and an outlet pipe 62 of helical feed pump 44 are rotatably mounted in bearings 64 mounted in bearing supports 188 secured to end plates 66 of a cylindrical heating enclosure 68, as best seen in Figure 3. The enclosure is mounted on legs 69 (Figure 1) resting on a metal support frame 71, which in turn is mounted on a concrete slab. The feed pump 44 is rotatably driven by any suitable drive motor 70 (Figures 1-3). The drive shaft 72 of motor 70 is drivingly coupled through a gear reducer 74 to feed pump 44 by a drive pulley 76 on drive shaft 72 driving a pulley 78 on pump outlet pipe 62 through a chain or belt connection 79. The heating means for heating enclosure 68 comprises a closed end sparge pipe 80 (Figure 2) extending into the enclosure adjacent the bottom thereof. The lower surface of pipe 80 has a plurality of radially extending holes 82 therethrough. A source of steam is connected through valves 84 (Figure 1) to the open end of pipe 80 for introducing steam under pressure through pipe 80 and holes 82 therein for heating enclosure 68. Condensate from the inner periphery of enclosure 68 and external surface of helical feed pump 44 collects at the bottom of enclosure 68 to form a pool of condensation within which pipe 80 is submerged. A condensate outlet 85 in enclosure 68 is provided to control the level of the condensate pool in enclosure 68. The submerged pipe, arrangement of steam outlet holes 82 and condensate function to prevent the feed pump coils 52 from overheating by maintaining the steam in a saturated condition. Without this arrangement, the steam would become superheated resulting in deleterious "burn on" of the food product 10 on the inner surface of the coils. The condensing temperature within heating enclosure 68, which is measured by a temperature gauge T1 on top thereof, can be controlled by regulating the steam pressure or by the introduction of a noncondensing gas, such as air, for example. For condensing temperatures above 100° C, steam alone under pressure is satisfactory. For condensing temperatures below 100°C, it is necessary to introduce air into the heating enclosure to control the condensing temperature while maintaining a pressure greater than atmospheric. A condensing temperature vent arrangement 87 is required to control the respective partial pressures of the steam and noncondensing gas (air) at temperatures below 100°C. The heating enclosure is further provided on top thereof with a normal pressure gauge 86 and steam relief valve 88, for example. With reference to Figures 1, 10 and 10A, outlet pipe 62 of helical feed pump 44 discharges food product 10 and gas through an inlet pipe 90 into a separator 92. The outlet and inlet pipes 62, 90, respectively, have flanges, as best seen in Figure 1, that are secured together by any suitable means, not shown. A sluiceway 94 of U-shaped cross-section in separator 92 has one end in alignment with and connected to inlet pipe 90, and is angled downwardly for guiding the food product toward the discharge end 98 of the separator. A food product level switch LS-2 is provided at the lower end of the separator to sense the level of the food product and to actuate an alarm, not shown, if the food product reaches that level. The pressurized gas emitted through inlet pipe 90 escapes from separator 92 through a vent 100 in the top wall of the separator. Windows 102 are provided in the top wall of separator 92 to allow the operator to observe the separator in operation. Separator 92 is further provided with a cleaning nozzle 96 at the upper end thereof through which liquid or steam may be directed for cleaning the separator. The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the invention as defined in the claims.

Claims: A method for continuously sterilizing a food product made up of food chunks immersed in a liquid without damaging the food chunks, consisting of the steps of: feeding a continuous stream of food product (10) to be processed and feeding a gas into the inlet (42) of a rotating helical feed pump (44) rotatably mounted in a heating enclosure (68) in which the food product is heated to a predetermined temperature in the helical feed pump (44); feeding the food product and gas from the feed pump (44) into a separator (92) which separates the gas from the food product; and feeding the food product from the separator (92) into a container; said predetermined temperature being selected so that the temperature of the food product remains at least at the sterilization temperature for a time sufficient to sterilize the food product. An apparatus for continuously sterilizing a food product made up of food chunks immersed in a liquid without damaging the food chunks, consisting of: first means (44) for transporting and heating the food product (10) to a predetermined temperature; second means (14) for continuously feeding the food product (10) and for feeding a gas into said first means (44); separator means (18) in product communication with said first means (44) for separating said gas from the food product; and means (106) for feeding the food product (10) from the separator means (18) into a container; said predetermined temperature being selected so that the temperature of the food product (10) remains at least at the sterilization temperature for a time sufficient to sterilize the food product. An apparatus according to claim 2 wherein said first means comprises a helical feed pump (44) and a gas accumulator (56) provided at the inlet thereof for receiving said food product (10) and gas, and said second means (14) comprises a conduit (40) having an outlet (42) in food product communication with said gas accumulator (56). An apparatus according to claim 3 wherein said gas accumulator (56) is cylindrical, and the axis of said gas accumulator is radially offset from the axis of said helical feed pump (44). An apparatus according to claim 4 wherein said helical feed pump (44) has a radially extending inlet leg (58) and said gas accumulator (56) is positioned so that lines extending through the axes of said feed pump and said accumlator (56) form an angle of about 45° with said inlet leg (58). Apparatus according to any one of claims 3-5 and including a gas feed pipe (48) through which gas is fed into the gas accumulator (56) and wherein the gas and food product are fed continuously into the helical feed pump (44). An apparatus according to claim 2, 3 or 4 wherein said helical feed pump (44) has a radially extending inlet leg (58) connected to said gas accumulator (56), and a guiding device (49) in said gas accumulator (56) connecting said outlet (42) of said conduit to said inlet leg (58) for guiding food product through the gas accumulator (56). An apparatus according to any one of claims 2-5, in which the accumlator (56) comprises a food product guiding device (49) connected between the food product feed tube (42) and the inlet leg (58), while allowing gas to pass out of the guiding device (49) into the accumulator body. An apparatus according to claim 7 or 8 wherein said guiding device (49) comprises a plurality of parallel spaced apart rods (51) arranged to form a tubular path for the food products.

Inventors: ATHEY, RODERICK ELWYN, MCFARLANE, DONALD PATRICK
Applicants: GRAHAM CORPORATION
Application year: 1987
Main classification: A23L3
IPC codes: A23B7, B65B55, A23L3