MICROWAVE PACKAGE FOR HAMBURGERS AND FRENCH FRIES

Abstract: A packaged food article for heating in a microwave oven comprises at least one farinaceous layer (11, 12). The farinaceous layer or layers (11, 12) is contained in a microwave shielding dish (10) arranged so that the upper edge (16) of the opening of the dish is level with the uppermost surface (18) of the farinaceous layer or layers. A layer of edible filling material (13) lies on top of the uppermost farinaceous layer (12) and completely closes the open top of the dish. The food article is sold frozen and can be microwaved from the frozen state. The farinaceous layers may be two halves of a burger bun and the layer of edible filling material may be a burger patty.

Description: MICROWAVE PACKAGE FOR HAMBURGERS AND FRENCH FRIES The present invention relates to packaged food articles and more particularly to articles which can be heated in microwave ovens. There is an increasing demand for food articles which can be prepared for consumption simply by heating, typically from frozen, in a microwave oven. Popular convenience foods include sandwiches, particularly burgers and hot dogs and the like, comprising an edible filling material between two layers of farinaceous material, typically bread in the form of a sliced roll or bun. Although frozen burger patties have themselves been available for a long time and can be heated from a frozen state in a microwave oven reasonably satisfactorily, there are problems with prepackaged frozen sandwiches which include the bun as well as the patty filling. If a burger complete with bun is microwave heated from the frozen state, by the time the patty has been defrosted and heated adequately, the bread bun becomes either completely dried out or at least rubbery and generally unpalatable. There have been a number of attempts in the prior art to resolve this problem. US-A-4015085 discloses a frozen sandwich combination comprising two farinaceous layers with a filler layer on top, the whole being enclosed and sealed in a non metallic film package. A dish of microwave reflecting material is located under the lower farinaceous layer. It is said that the dish partly shields the bread base of the package so as to alter the character of the heating of the bread base to yield a palatable product while still heating the meat filling material to a high temperature. It is believed, however, that the arrangement disclosed in the above patent specification does not provide satisfactory results. No product resembling tha shown in the U.S. patent has been successfully marketed even though the patent itself issued nearly 20 years ago. GB-A-1484929 discloses a carton containing two halves of a burger bun and a meat patty on top of the two halves. The carton is lined on a base and four sidewalls with a microwave shield material. It is said that the whole carton can then be microwave heated by inverting the package, so that the patty is lowermost, and placing in a microwave oven. It is said that sufficient microwave energy penetrates through the unshielded top of the carton (at the bottom when heating) to heat the patty without excessively heating the bread layers. To avoid problems of arcing between adjacent edges of the shielding material, gaps are left in the shield up the corners of the carton. Again, it is believed that the product described in the above patent has not proved satisfactory. Nothing corresponding to this product has ever emerged on the market, even though food manufacturing companies have been looking continuously during this period for a solution to the problem of providing a satisfactory microwave heatable combination burger and bun. According to the present invention, a packaged food article for heating in a microwave oven comprises at least one farinaceous layer having a predetermined thickness, a dish of microwave shielding material having a base extending continuously under the lowermost surface of the farinaceous layer or layers and a sidewall extending from the base continuously up the sides of the farinaceous layer or layers, the sidewall having an upper edge defining an open top of the dish, the sidewall having a height from the base so that the uppermost surface of the farinaceous layer or layers is substantially level with said upper edge when the farinaceous material is warmed, and located on top of said uppermost surface a layer of edible filling material, said filling material layer extending completely over said uppermost surface substantially to said upper edge round the whole periphery of the open top of the dish. With the above arrangement, microwave energy is in fact substantially completely excluded from the farinaceous layers. The bottom and sides of the farinaceous layers are protected by the shielding dish which extends continuously over the whole base of the farinaceous layers and right up the sides level with the top of the farinaceous layers. The filling material layer, typically a burger patty, is then arranged to extend completely over the top surface of the farinaceous layers right up to the edge of the dish right around the periphery. Generally, the filling material has a water and/or fat content which is much greater than that of the farinaceous layers, and is also made of a thickness so that, once defrosting is underway, microwave energy cannot substantially penetrate through the filling material layer. Since the arrangement is made to minimise and preferably eliminate any gaps between the filling material layer and the top edges of the shielding dish, microwave energy is excluded from the interior of the dish containing the farinaceous layers. In practice, said filling material layer may have transverse dimensions greater than the transverse dimensions of the open top of the dish so that said filling material layer can extend outside said upper edge. Where the dish is formed with a flange extending outwards from said upper edge in the plane of the open top, the transverse dimensions of said filling material may be less than the transverse dimensions of the outer periphery of said flange so that said filling material layer can be located inside said outer periphery. Normally, the packaged food article includes a microwave transparent carton containing said layers and said dish, whereby steam evolved during microwave heating is partially confined within the carton. It has been found that fully adequate heating of the farinaceous layers is achieved relying on conductive and convective heating primarily from the evolved steam trapped within the carton. The carton may have internal lateral dimensions to fit the outer periphery of said flange allowing minimal lateral movement of the dish within the carton. The flange typically has a uniform width and said transverse dimensions of said filling material layer may exceed the transverse dimensions of the open top of the dish by approximately said uniform width. In this way, even if the filling material layer is dislodged in the carton to touch the sides of the carton, thereby on one side becoming vertically aligned with the outer periphery of the flange of the dish, the opposite edge of the filling material layer will still be substantially aligned with the inner edge of the flange, i.e. the upper edge of the dish wall, thereby still substantially closing off the open top of the dish. Normally the carton is formed of cardboard. In a preferred arrangement, the microwave transparent carton further contains a plurality of parallel partitions formed from microwave absorbing material, said partitions extending within the carton to provide a plurality of parallel side-by-side elongate chambers each for holding at least one food stick to be heated by conduction or radiation from the microwave absorbing material. The food sticks are normally potato chips or "fries". Reference may be made to U.S. Patents Nos. 4943439, 5034234 and 5084601 for further details of these microwave absorbing partitions and structures for microwave heating and cooking french fries. Preferably, said parallel partitions are arranged in said microwave transparent carton below said dish. Then said carton may have an opening in at least one face of the carton perpendicular to said elongate chambers and aligned with ends of said chambers to allow steam evolved by said food sticks during heating to leave the carton. In this way, sufficient ventilation is provided to the food sticks to prevent excess steam from damaging the texture and consistency of the product. Conveniently, said opening does not extend above the base of the dish so that evolved steam is trapped in the upper part of the carton around the dish, thereby providing appropriate heating of the farinaceous layers within the dish. Typically, the carton is wrapped in a packing film which is to be removed before microwave heating. The dish may be formed from paper with a layer of foil laminated on the surface thereof. This foil layer may be on the inner surface of the formed dish. Instead the dish may be formed of aluminium foil. In any case, said dish is preferably sufficiently ridged to be self supporting. The edible filling material is typically a meat, fish or poultry product, a substitute for one of these or a vegetable product. In a preferred arrangement, said filling material layer is made to be thinner in the centre and thicker around its periphery. It has been found that this shape improves uniformity of heating. Normally, the layers and dish are circular. The present invention also contemplates a packaged food article for heating in a microwave oven comprising a microwave transparent carton and a plurality of parallel partitions of microwave absorbing material extending within the carton to provide a plurality of parallel side-by-side elongate chambers, each for holding at least one food stick to be heated by conduction or radiation from the microwave absorbing material, the carton also containing above said chambers a dish of microwave shielding material, at least one farinaceous layer in said dish to be shielded by the dish, and a layer of edible filling material on top of the uppermost farinaceous layer so as to be above the dish, said carton having an opening in at least one face of the carton perpendicular to said elongate chambers and aligned with the ends of said chambers to allow steam evolved by said food sticks during heating to leave the carton. Preferably, said opening does not extend above the base of the dish so that evolved steam is trapped in the upper part of the carton around the dish. Examples of the invention will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-sectional view through a packaged food article embodying the present invention,- Figure 2 is a cross-sectional view of a further embodiment of the invention incorporating an outer carton; and Figure 3 is a perspective view of the embodiment of Figure 2 with part of the outer carton broken away. Referring to Figure 1, the packaged food article comprises a microwave shielding dish 10 containing two farinaceous layers, 11 and 12, comprising the two halves of a burger bun. A burger patty 13 lies on top of the upper half of the bun 12. The dish 10 is formed of a material which is reflective to microwaves. The dish has a continuous base 14 extending completely under the lowermost surface of the lower half 11 of the bun. A sidewall 15 of the dish extends up the sides of the two layers 11 and 12 of the bun to an upper edge 16 defining an open top 17 of the dish 10. The relative sizes of the dish 10 and the two halves 11 and 12 of the burger bun are important. As shown in Figure 1, the uppermost surface 18 of the upper half 12 of the bun is substantially aligned with the open top of the dish 10 in the plane of the upper edge 16 of the sidewall 15. Further, it is desirable that there are minimal gaps between the outer peripheral edge 19 of the upper half 12 of the bun and the surrounding upper edge 16 of the dish 10. In the drawing, the dish 10 is shown to have a sidewall 15 which leans outwards slightly from the vertical. This structure is solely for ease of manufacture of the dish. In order for the upper half 12 of the bun to fit snuggly within the dish, the lower half 11 may be slightly compressed. The dish 10 can be made in any convenient manner known in the art to produce a continuous microwave shield fully over the base 14 and sidewall 15. In one example, the dish 10 is formed from paper board laminated with a thin layer of aluminium foil on one surface. The laminated board is then pressed to form the dish shape as illustrated in Figure 1. These pressed paper dishes can be obtained from Tenneco Packaging, Pressware Division, Bath, England. Preferably, the thin aluminium foil layer is on the inside of the dish, so that the exterior of the dish has the appearance of paper. The dish is formed with an outwardly extending flange 20 in the plane of the upper edge 16 of the sidewall 15. The burger patty 13 lies on top of the uppermost surface 18 of the upper half 12 of the burger bun, as shown in Figure 1. The patty 13 has a diameter which is slightly greater than the diameter of the bun 12, and is in fact greater than the diameter of the opening 17 in the top of the dish, so that the patty 13 rests on the upper edge 16 of the sidewall 15 right around the opening. In this way, the patty 13 effectively closes the open top of the dish. When the resulting combination is heated in a microwave oven, the combination of the shielding dish 10 and the patty 13 completely covering the open top of the dish, substantially excludes microwaves from the interior of the dish. However, microwaves cam be absorbed in the patty 13 to defrost and heat the patty as required. The bun halves 11 and 12, meanwhile-., are not exposed to substantial microwave energy and are defrosted and heated gently from other sources, including heat conducted down from the patty 13 and heat conducted inwards through the base and walls of the dish 10 from the external atmosphere. It has been found important to ensure that there are no substantial gaps between the outer peripheral edge of the patty 13 and the upper edge 16 of the sidewall 15 of the dish 10. It is also preferable to ensure that the upper half 12 of the bun substan ially completely fills the opening in the dish so that there are no significant gaps between the outer peripheral edges of the upper half 12 of the bun and the inner face of the sidewall 15 of the dish 10 at the upper edge 16. Gaps should be less than 5 mm and preferably not more than l mm. It is also important that the sidewall 15 of the dish extends right up to the uppermost surface of the upper half 12 of the bun. In practice, when the dish 10 is filled with the two halves of the bun and the cooked patty 13 placed on top ready for freezing, the upper half 12 of the bun may extend slightly proud of the open top of the dish after freezing. However, what is important is that when the bun begins to defrost and soften during microwave heating, it sinks down again under the weight of the patty 13, so that the upper surface does not extend above the upper edge 16 of the sidewall 15. As shown in Figure 1, the burger patty 13 is made to be slightly thinner in the centre compared to the edges. It has been found that this facilitates even heating of the patty in the microwave oven. Normally, the bun and patty combination shown in Figure 1 is provided contained in a cardboard carton. The carton may be sized so as just to fit the outer peripheral edges 21 of the flange 20 of the dish 10, so that the dish 10 is restrained against lateral movement within the carton. Then, the burger patty 13 can be made to have a diameter which exceeds that of the open top 17 of the dish 10 by the width of the flange 21. With the patty 13 centrally located over the dish 10, the edges of the patty then extend halfway out over the flange 20 on both sides as shown in Figure 1. Importantly, if the patty 13 is dislodged to one side within the carton, so that one edge becomes aligned with the outer edge 21 of the flange 20, then the opposite edge will still be substantially aligned with the upper edge 16 of the sidewall 15 preventing any substantial gap between the dish 10 and the patty 13. Before microwave heating, any film wrapping over the carton is first removed. The carton containing the dish 10, bun halves 11 and 12, and patty 13 is then placed the correct way up (with the patty 13 on top) in the microwave oven for heating. After the specified heating time, the carton can be removed and opened to remove the dish with patty lying on top. The patty 13 should be very hot, but the bun halves 11 and 12 should be simply thawed and warm without having been damaged by excessive exposure to microwave energy. The burger can then be made ready for βctting by breaking open the side of the dish 10 removincr the bun half with the patty on top, placing the lower bun half on top of the patty to form the usual sandwich, and eating by hand in the usual way. Lines of weakness may be provided down opposite sides of the sidewall 15 of the dish 10 to enable the dish to be split open easily to reveal the two halves of the bun. Relish or sauce may be included conveniently between the patty 13 and the uppermost surface of the upper half 12 of the bun. In this way the relish or sauce is protected during packaging and carriage by the patty 13. Then, the lower half 11 of the bun as located in the dish 10 may be formed by the base of a burger bun, and the upper half 12 may form the top of a burger bun. When the bun is reconstructed after heating, the base 11 is first placed on top of the patty 13 and the bun then inverted for consumption the usual way round, with the sauce or relish (or cheese) lying on top of the burger patty 13. - 11 - Referring now to Figure 2, the assembly of Figure 1 is shown contained inside a carton 22. Also within the carton 22 is contained an inner box 23 containing a number of vertical and horizontal partitions 24 and 25. The partitions 24 and 25 are formed of a microwave absorbing or susceptive material. The partitions are in adjacent vertical and parallel planes respectively and between them form a number of elongate chambers 26. Each chamber 26 contains a french fry or chip. When the package is heated in a microwave oven, the partitions 24 and 25 absorb microwave energy and heat up so that the french fries contained in the chambers 26 are heated and cooked by conduction and radiation of heat from the partitions 24. In this way, the microwave absorbing material can crisp, toast or brown the surfaces of the french fries or other food sticks contained in the chambers 26. Reference may be made to the above referred U.S. Patents for further details of the microwave absorbing material and structures for heating french fries. The complete package illustrated in Figure 2 can be heated from frozen in a microwave oven to produce a combination meal comprising both a burger and french fries. The complete package is illustrated in more detail in Figure 3 which shows the patty 13 lying over the open top of the microwave shielding dish 10 containing the two halves of the bun. The dish 10 rests on top of the inner box 23 containing the microwave absorbing partitions 24 and 25. The box 23 is usually completely open at one end 30 revealing the ends of the chambers 26. At the opposite end 31 the box 23 is closed apart from small windows 32. In this way, when the combination food package has been heated, the french fries contained in the box 23 can easily be tipped out through the open end 30. The sidewall 33 of the carton 22 adjacent the closed end 31 of the french fries box 23 is provided with an opening 34 immediately opposite the end 31 to expose the small openings 32 in the end wall 31. The opening 34 in the sidewall of the carton 22 does not extend above the upper surface of the box 23, or the base of the dish 10. The purpose of the window 34 in the carton 22 is to ventilate the lower part of the carton 22 to prevent the french fries being exposed to excessive levels of moisture from steam trapped within the carton. On the other hand, because the opening 34 does not extend above the base of the dish 10, the steam evolved during heating is substantially trapped within the upper part of the carton, though the carton is not of course intended to be airtight. By trapping a substantial amount of steam around the dish 10, adequate defrosting and heating of the bun contained within the dish 10 is ensured, even though the combination of the patty 13 and dish 10 substantially prevents microwave energy from penetrating to the bun. At the same time, the window 34 ensures that the french fries are adequately ventilated to provide a desirable crisp texture and brown colour for the french fries. In a particular example, the two halves 11 and 12 may together form a burger bun of which the baked weight is about 60 grams. The nominal diameter of the bun is 100 mm and the nominal height of the whole bun is 35 mm. The dish 10 is formed also with a depth of 35 mm. and a diameter at the top opening of 102 mm. The diameter at the base of the dish may be about 86 mm. The patty 13 may have a diameter of about 108 mm. The width of the flange 21 around the open top of the dish may be about 6 mm. The entire package may include an outer film wrapping to seal the contents and maintain hygiene. This outer wrapping is removed before microwave heating. Although the above examples have been described by reference to a burger with a patty, usually beef, the invention is also applicable to other forms of sandwich comprising a edible filling layer between two farinaceous layers. The farinaceous layers may be slices of bread or halves of a bun. The filling may be meat, poultry, fish or vegetarian substitutes for these. In addition to a patty the filling may include cheese, sauce or relish. Instead of french fries, the sandwich may be packed with some other form of vegetable accompaniment such as a hashbrown patty.

Claims: CLAIMS 1. A packaged food article for heating in a microwave oven comprising at least one farinaceous layer having a predetermined thickness, a dish of microwave shielding material having a base extending continuously under the lowermost surface of the farinaceous layer or layers and a sidewall extending from the base continuously up the sides of the farinaceous layer or layers, the sidewall having an upper edge defining an open top of the dish, the sidewall having a height from the base so that the uppermost surface of the farinaceous layer or layers is substantially level with said upper edge when the farinaceous material is warmed, and located on top of said uppermost surface a layer of edible filling material, said filling material layer extending completely over said uppermost surface substantially to said upper edge round the whole periphery of the open top of the dish. 2. A packaged food article as claimed in Claim 1 wherein said filling material layer has transverse dimensions greater than the transverse dimensions of the open top of the dish so that said filling material layer can extend outside said upper edge. 3. A packaged food article as claimed in Claim 2 wherein the dish is formed with a flange extending outwards from said upper edge in the plane of the open top and the transverse dimensions of said filling material are less than the transverse dimensions of the outer periphery of said flange so that said filling material layer can be located inside said outer periphery. 4. A packaged food article as claimed in any preceding claim and including a microwave transparent carton containing said layers and said dish, whereby steam evolved during microwave heating is partially confined within the carton. 5. A packaged food article as claimed in Claim 4 as dependent on Claim 3 wherein the carton has internal lateral dimensions to fit the outer periphery of said flange allowing minimal lateral movement of the dish within the carton. 6. A packaged food article as claimed in Claim 5 wherein the flange has a uniform width and said transverse dimensions of said filling material layer exceed the transverse dimensions of the open top of the dish by approximately said uniform width. 7. A packaged food article as claimed in any of Claims 4 to 6 wherein said carton is formed of cardboard. 8. A packaged food article as claimed in any of Claims 4 to 7 wherein said microwave transparent carton further contains a plurality of parallel partitions formed from microwave absorbing material, said partitions extending within the carton to provide a plurality of parallel side-by-side elongate chambers each for holding at least one food stick to be heated by conduction or radiation from the microwave absorbing material. 9. A packaged food article as claimed in Claim 8 wherein said parallel partitions are arranged in said microwave transparent carton below said dish. 10. A packaged food article as claimed in Claim 9 wherein said carton has an opening in at least one face of the carton perpendicular to said elongate chambers and aligned with ends of said chambers to allow steam evolved by said food sticks during heating to leave the carton. 11. A packaged food article as claimed in Claim 10 wherein said opening does not extend above the base of the dish so that evolved steam is trapped in the upper part of the carton around the dish. 12. A packaged food article as claimed in any of Claims 4 to 11 wherein the carton is wrapped in a packing film which is to be removed before microwave heating. 13. A packaged food article as claimed in any preceding claim wherein said dish is formed from paper with a layer of foil laminated on a surface thereof. 14. A packaged food article as claimed in Claim 8 wherein the foil layer is on the inner surface of the formed dish. 15. A packaged food article as claimed in any one of Claims 1 to 7 wherein said dish is formed of aluminium foil. 16. A packaged food article as claimed in any preceding claim wherein said dish is sufficiently rigid to be self-supporting. 17. A packaged food article as claimed in any preceding claim wherein said edible filling material is a meat, fish or poultry product, a substitute for one of these, or a vegetable product. 18. A packaged food article as claimed in any preceding claim wherein said filling material layer is made to be thinner in the centre and thicker around its periphery. 19. A packaged food article as claimed in any preceding claim wherein the layers and dish are circular. 20. A packaged food article as claimed in any preceding claim wherein there are two of said farinaceous layers stacked one on top of the other. 21. A packaged food article for heating in a microwave oven comprising a microwave transparent carton and a plurality of parallel partitions of microwave absorbing material extending within the carton to provide a plurality of parallel side-by-side elongate chambers, each for holding at least one food stick to be heated by conduction or radiation from the microwave absorbing material, the carton also containing above said chambers a dish of microwave shielding material, at least one farinaceous layer in said dish, to be shielded by the dish, and a layer of edible filling material on top of the or the uppermost farinaceous layer so as to be above the dish, said carton having an opening in at least one face of the carton perpendicular to said elongate chambers and aligned with ends of said chambers to allow steam evolved by said food sticks during heating to leave the carton. 22. A packaged food article as claimed in Claim 21 wherein said opening does not extend above the base of the dish so that evolved steam is trapped in the upper part of the carton around the dish.

Inventors: BRANDBERG LAWRENCE C, RISCH SARA J, BRANDBERG, LAWRENCE, C., RISCH, SARA, J.
Applicants: BRANDBERG LAWRENCE C, CONAGRA FOODS LTD, RISCH SARA J, BRANDBERG, LAWRENCE, C., CONAGRA FOODS LIMITED, RISCH, SARA, J.
Application year: 1996
Main classification: B65D81
IPC codes: B65D81