Contact members for packaged articles heated with radio frequency energy
Heating systems utilizing radio frequency (RF) energy and methods for using the same to rapidly and uniformly heat packaged articles moving through the system on one or more convey lines. These systems may be useful for a variety of processes, including the pasteurization or sterilization of packaged foodstuffs.
1. A process for sterilizing or pasteurizing packaged articles using radio frequency (RF) energy, said process comprising:
(a) loading a plurality of said articles onto a conveyance system in a loading zone, wherein said loading includes initiating contact between the packages of said articles and contact surfaces of article contact members of said conveyance system, wherein said contact surfaces have an initial contact surface temperature immediately before contacting the packages of said articles in said loading zone;
(b) transporting said articles through an RF heating zone via said conveyance system while supporting said articles with said article contact members and maintaining the packages of said articles in contact with said contact surfaces, wherein each of said article contact members comprises an energy absorptive component having a dielectric constant in the range of 20 to 150 and a dielectric loss factor in the range of 10 to 1500;
(c) simultaneously with said transporting, heating said articles and said contacting members using RF energy discharged into said RF heating zone, wherein said heating causes the temperature of the geometric center of said articles to increase by at least 20° C., wherein said heating causes the temperature of said contact surfaces of said article contact members to increase by at least 10° C. to a maximum contact surface temperature;
(d) unloading said articles from said conveyance system in an unloading zone, wherein said unloading includes removing the packages of said articles from contact with said contact surfaces of said article contact members;
(e) returning said article contact members from said unloading zone to said loading zone to repeat said loading of step (a) with additional articles; and
(f) subsequent to said heating of step (c) and prior to repeating said loading of step (a), cooling the temperature of said contact surfaces of said article contact members to a temperature at least 10° C. below the maximum contact surface temperature.
2. The process of claim 1 , wherein said articles transported through said RF heating zone are not placed in multi-article carriers.
3. The process of claim 1 , wherein said conveyance system comprises two or more convey lines arranged in series.
4. The process of claim 1 , wherein said conveyance system comprises a continuous convey line extending from said loading zone to said unloading zone.
5. The process of claim 1 , further comprising, prior to said heating of step (c), passing said articles through an initial thermal regulation zone and, subsequent to said heating of step (c), passing said articles through a subsequent thermal regulation zone.
6. The process of claim 5 , wherein said articles are not supported by said article contact members in said initial and subsequent thermal regulation zones.
7. The process of claim 5 , wherein said loading of step (a) is carried out prior to passage of said articles through said initial thermal regulation zone and said unloading of step (d) is carried out subsequent to passage of said articles through said subsequent thermal regulation zone.
8. The process of claim 5 , wherein said loading of step (a) is carried out subsequent to passage of said articles through said initial thermal regulation zone and said unloading of step (d) is carried out prior to passage of said articles through said subsequent thermal regulation zone.
9. The process of claim 1 , wherein said cooling of step (f) includes passing said article contact members through a liquid having a temperature that is less than said maximum contact surface temperature.
10. The process of claim 1 , wherein said energy-absorptive component includes an energy-absorptive material having a conductivity in the range of from about 0.01 Siemens per meter (S/m) to about 10 S/m.
11. The process of claim 1 , wherein each of said article contact members comprises an insulating component having a dielectric loss factor of not more than 10, wherein said contact surfaces of said article contact members are presented by said insulating components, wherein at least a portion of said insulating components are positioned between said energy absorptive component and the packages of said articles during said heating of step (c), wherein each of said insulating components comprises a layer of an insulating material covering at least a portion of said energy absorptive component.
12. The process of claim 11 , wherein said insulating component surrounds the energy-absorptive component.
13. The process of claim 1 , wherein each of said article contact members comprises a polymeric material surrounding an electrolyte material.