Apparatus for continuous microwave sterilization of food in pouches

• US 3,961,569 A
• Filed: 08/15/1974
• Issued: 06/08/1976
• Est. Priority Date: 08/15/1974
• Status: Expired due to Term

• Current Assignee: The United States Of America As Represented By The Secretary Of The Army
• Original Assignee: The United States Of America As Represented By The Secretary Of The Army
• Inventors: Berkowitz, Daniel, Kenyon, Ernest M., Ayoub, John A.
• Primary Examiner(s): Wilhite, Billy J.
• Assistant Examiner(s): Niegowski, James A.
• Application Number:
  US05/497,789
• Time in Patent Office: 663 Days
• Field of Search: 219/10.55 A, 219/10.55 E, 21/54 R, 21/102 R, 99/349, 99/355, 99/360, 99/361, 99/362, 99/443 R, 99/443 C, 99/451, 99/470, 99/483, 198/184, 198/193
• US Class Current: 99/451
• CPC Class Codes: A23L 3/01 using microwaves or dielectric heating
• CPC Class Codes: A23L 3/04 with packages on endless chain or band conveyors A23L3/022 takes precedence

Abstract

An apparatus for sterilizing food packaged in flexible pouches in a contius process employing microwaves for heating the food within the sealed flexible pouches to sterilizing temperatures. The pouches of food are conveyed thru the apparatus between a pair of conveyor belts which are permeable to microwaves and which comprise a layer of thermal insulation which is also permeable to microwaves. The pouches are also permeable to microwaves. The apparatus is pressurized to prevent bursting of the flexible pouches at the high sterilizing temperatures attained.

Claims

1. Apparatus for sterilizing food sealed in flexible, microwave-permeable pouches, including in combination:

a tunnel pressurized above atmospheric pressure comprising a microwave heating section, a temperature maintenance section, and a cooling section, said microwave heating section having a source of microwaves for heating said food to sterilizing temperatures, said temperature maintenance section comprising a space wherein said food sealed in said flexible, microwave-permeable pouches is maintained at said sterilizing temperatures after said food passes out of said microwave heating section for a length of time sufficient to accomplish sterilization of said food, said cooling section having means for reducing the temperature of said food after sterilization thereof sufficiently to prevent bursting of said pouches when exposed to the atmosphere outside of said pressurized tunnel,

means for introducing said flexible, microwave-permeable pouches into said pressurized tunnel at an entrance end thereof while an atmosphere of predetermined pressure above atmospheric pressure is maintained within said pressurized tunnel,

means for removing said pouches from said pressurized tunnel at an exit end thereof while an atmosphere of predetermined pressure above atmospheric pressure is maintained within said pressurized tunnel,

two parallel, spaced apart, heat-insulated, endless conveyor belts, one of said conveyor belts being positioned above the other of said conveyor belts and spaced from said other conveyor belt a distance which is substantially equal to the thickness of said flexible pouches of food, said conveyor belts being contained within said microwave heating section and said temperature maintenance section of said pressurized tunnel, at least one of said two parallel, spaced apart, heat-insulated, endless conveyor belts being microwave-permeable,

a third endless conveyor belt contained within said cooling section of said pressurized tunnel,

means for driving each of said endless conveyor belts,

said two parallel, spaced apart, heat-insulated, endless conveyor belts being adapted to receive said flexible pouches of food from said introducing means and to convey said flexible pouches of food therebetween through said microwave heating section and said temperature maintenance section of said pressurized tunnel and to deposit said flexible pouches of food in succession onto said third endless conveyor belt,

said third endless conveyor belt being adapted to receive said flexible pouches of food from said two parallel, spaced apart, heat-insulated, endless conveyor belts and to convey said flexible pouches of food through said cooling section of said pressurized tunnel and to discharge said flexible pouches of food from said cooling section into said removing means;

whereby said food sealed in said flexible pouches is irradiated by said microwaves while said pouches are being conveyed through said microwave heating section, said food being heated by said microwaves to temperatures effective for sterilizing said food, at which temperatures said pouches are held while being conveyed through said temperature maintenance section wherein said food becomes sterilized, said flexible pouches of food thereafter being cooled while being conveyed through said cooling section sufficiently to prevent bursting of said pouches when exposed to the atmosphere outside of said pressurized tunnel, said flexible pouches of food being discharged from said third conveyor belt into said removing means and thereafter being discharged from said removing means into the atmosphere outside of said pressurized tunnel in a sterilized condition.

2. Apparatus according to claim 1, wherein said introducing means is an airlock comprising a plurality of compartments isolated from each other for receiving, holding for a predetermined period of time, and then discharging pouches of food one at a time as said pouches of food are being introduced from the outside atmosphere into said pressurized tunnel at said entrance end thereof, and said removing means is an airlock comprising a plurality of compartments isolated from each other for receiving, holding for a predetermined period of time, and then discharging pouches of sterilized food one at a time as said pouches of sterilized food are being removed from said pressurized tunnel at said exit end thereof into the outside atmosphere.

3. Apparatus according to claim 1, wherein both of said two parallel, spaced apart, heat-insulated, endless conveyor belts are microwave-permeable.

4. Apparatus according to claim 3, wherein both of said two parallel, spaced apart, heat-insulated, endless conveyor belts comprise a layer of microwave-permeable, foamed polymeric heat insulation.