Control of microwave interactive heating by patterned deactivation

Abstract

A patterned microwave interactive element and laminate including a patterned microwave interactive element for use in forming food packaging materials that may be employed to store and subsequently cook the food stored therein are provided. The pattern of the microwave interactive element is selected to focus the heat generated to predetermined areas of the food contained in the packaging. Areas where the microwave interactive element has been deactivated may be formed by a variety of methods, such as by demetallization, by the application of an inactivating chemical, by mechanical means and the like, to create a preselected pattern of inactive areas relative to the active areas, thereby controlling the temperatures produced in different sections of the packaging material. Optimum browning and/or crisping of the microwave heated food product may be achieved by selecting a pattern of microwave interactive and inactive areas tailored to specific food products.

We claim: 
     
       1. A microwave interactive heating element capable of converting microwave radiation to heat energy to heat a food product proximate to said heating element, wherein said element is formed of a layer of microwave interactive material supported on a substrate and said element includes a plurality of first areas having a reduced capability to generate heat in response to microwave radiation and a plurality of second areas having an unaltered capability to generate heater in response to microwave radiation arranged in a predetermined pattern relative to said first areas, wherein said pattern is formed by selectively deactivating without removing selected areas of said microwave interactive material from said substrate in the predetermined pattern to form said first areas and by leaving the remainder of said predetermined pattern untreated to form said second areas, thereby producing preselected temperature differences in said food product corresponding to said pattern when said heating element is subjected to microwave radiation. 
     
     
       2. The microwave interactive heating element of claim 1, wherein said first areas are arranged alternately with said second areas in concentric rings. 
     
     
       3. The microwave interactive heating element of claim 1, wherein said first areas are arranged to form a grid around said second areas. 
     
     
       4. The microwave interactive heating element of claim 1, wherein said first areas are formed in the shaped of discrete squares separated by a grid formed of said second areas. 
     
     
       5. The microwave interactive heating element of claim 1, wherein said first areas are arranged alternately with said second areas in parallel lines. 
     
     
       6. The microwave interactive heating element of claim 1, wherein the reduced capability of said first area to generate heat in response to microwave radiation is produced by the application of an inactivating chemical to said first area. ƒ7. The microwave interactive heating element of claim 1, wherein the reduced capability of said first area to generate heat in response to microwave radiation is produced by mechanically reducing the amount of microwave interactive material in said 
     
     
        first area. .]. 8. A microwave interactive heater for insertion into a container intended for the storage and cooking by microwave energy of a food product contained therein, said heater comprising: a. a supporting film;   b. a microwave interactive material deposited on the entire surface of one side of said film, and   c. a substrate supporting said film and said microwave interactive material, wherein first, deactivated areas have been formed in said microwave interactive material by the application of an inactivating chemical to reduce the capability of the first areas to generate heat in response to microwave radiation to create a predetermined pattern of said first areas relative to second areas untreated by said inactivating chemical so that the capability of said microwave interactive material in said second areas to generate heat in response to microwave radiation is   
     
     
        not affected by said inactivating chemical. 9. The microwave interactive heater of claim 8, wherein said first areas are arranged alternately with 
     
     
        said second areas in concentric rings. 10. The microwave interactive heater of claim 8, wherein said first areas are arranged to form a grid 
     
     
        around said second areas. 11. The microwave interactive heater of claim 8, wherein said first areas are formed in the shapes of discrete squares 
     
     
        separated by a grid formed of said second areas. 12. The microwave interactive heater of claim 8, wherein said first areas are arranged 
     
     
        alternately with said second areas in parallel lines. 13. The microwave interactive heater in claim 8, wherein said first areas are formed by inactivating said microwave interactive material in incremental steps to produce a temperature gradient when said laminate is subjected to 
     
     
        microwave radiation. 14. The microwave interactive heater of claim 8, wherein the sections of the food product in contact with said first areas are heated to a lower temperature than the sections of the food product in 
     
     
        contact with said second area. 15. A container for packaging several different foods, storing said foods and cooking said foods by microwave energy, said container including a plurality of heaters formed according to claim 8, wherein each heater is positioned in said container in contact with one of said foods and the pattern of first and second areas on said heater is selected to produce the optimum temperature required to brown or 
     
     
        crisp the food. 16. A method of producing patterns on the surface of a food product in contact with a heater element heated by microwave energy comprising the steps of: a. forming a beater element including a microwave interactive material that has been selectively inactivated to produce a preselected pattern of microwave active and microwave inactive areas wherein said microwave active areas are capable of browning the surface of said food product to a significantly greater degree than said microwave inactive areas;   b. placing said food product in contact with said heater element in a microwave oven;   c. subjecting said food product and said heater element to microwave energy for a time sufficient to differentially brown the surface of the food product in a pattern corresponding to said preselected pattern, wherein the surface of the food product in contact with the microwave active areas of said heater is browned to a substantially greater degree than the surface of the food product in contact with the microwave inactive areas   
     
     
        of said heater. 17. A method according to claim 16, wherein said food product is a hot dog and said preselected pattern comprise a plurality of parallel lines of alternating active and inactive areas, and in step (b) said hot dog is placed across the parallel lines of the pattern to contact said heater element so that following step (c) the surface of said hot dog is selectively browned in a pattern of parallel lines resembling grill 
     
     
        marks. 18. A method according to claim 16, wherein said food product is a pancake and said preselected pattern is a grid of active areas separating islands of inactive areas, and in step (b) said pancake is placed in contact with the grid pattern on the heater element so that following step (c) the surface of said pancake is selectively browned in a waffle-like 
     
     
        grid pattern. 19. A method of forming a heating element selectively responsive to microwave radiation for use in the microwave cooking of food products having portions that require browning or heating to different degrees, said method including the steps of: a forming a layer of microwave interactive material on a substrate to completely cover said substrate;   b. selecting a pattern of microwave interactive and microwave inactive areas that will produce the different amounts of heat required to optimally brown or heat the food product; and   c. applying a chemical capable of inactivating said microwave interactive material only to the areas said layer of microwave interactive material corresponding to said microwave inactive areas of said pattern to produce said microwave inactive areas, thereby forming said selectively responsive   
     
     
        heating element. 20. The method of forming a heating element described in claim 19, wherein said pattern comprises concentric rings of alternating 
     
     
        microwave interactive and microwave inactive areas. 21. The method of forming a heating element described in claim 19, wherein said pattern comprises parallel lines of alternating microwave interactive and 
     
     
        microwave inactive areas. 22. The method of forming a heating element described in claim 19, wherein said pattern comprises a grid with said microwave interactive areas forming discrete islands separated by lines of 
     
     
        microwave inactive areas. 23. The method of forming a heating element described in claim 19, wherein said pattern comprises a grid with said microwave inactive areas forming discrete islands separated by lines of 
     
     
        microwave interactive areas. .Iadd.24.  A microwave interactive heating element of claim 1, wherein said plurality of first areas are contiguous. .Iaddend. .Iadd.25. A microwave interactive heating element of claim 1, wherein said plurality of first areas are noncontiguous. .Iaddend. .Iadd.26. A microwave interactive heating element as defined in claim 1, wherein said second areas are contiguous. .Iaddend. .Iadd.27. A microwave interactive heating element as defined in claim 1, wherein said second areas are noncontiguous. .Iaddend. .Iadd.28. A microwave interactive heating element capable of converting microwave radiation to heat energy to heat a food product proximate to said heating element, wherein said element is formed of a layer of microwave interactive material supported on a substrate and said element includes a first area having a reduced capability to generate heat in response to microwave radiation and a second area having an unaltered capability to generate heat in response to microwave radiation arranged in a predetermined pattern, wherein said pattern is formed by selectively deactivating without removing a selected area of said microwave interactive material from said substrate in the predetermined pattern to form said first area and by leaving the remainder of said predetermined pattern untreated to form said second area. .Iaddend.