Abstract:
Improved cooking devices and methods of achieving good adherence contact between a low-friction, non-stick release sheet material and a heated food-supporting platen or cooking surface are provided. The adherence of the release sheet to the lower platen is sufficiently good to permit removal of cooked items such as hamburger patties with a spatula without significantly adversely disturbing the release sheet. In addition, good heat transfer is achieved to permit good sear (good carmelization and good browning) on the bottom surface of foods, including hamburger patties. In addition, inventive cooking utensils and methods are provided that incorporate or use release sheets in the utensils themselves, so that the benefits of a release sheet on the food-supporting platen or cooking surface are achieved.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to cooking devices and to methods of cooking food items on a grill, griddle or other flat surface. More particularly, the invention relates to devices and methods of cooking food on a flat surface and removing the food therefrom in which removable, disposable, flexible, non-stick sheets are utilized. 
       BACKGROUND OF THE INVENTION 
       [0002]    A need exists for improved devices and methods for cooking relatively large quantities of food, particularly food such as hamburger patties in quick service restaurants. 
         [0003]    Typically, clamshell grills are utilized that have top and bottom (upper and lower) heated cooking platens. The food items to be cooked, typically a plurality of items, such as, for example, 6, 9, 12 or more hamburger patties, are placed on the lower platen. The upper platen is closed onto and in contact with the food items on the lower platen so that both sides of the food items are cooked simultaneously. When cooking is completed, the upper platen is raised and the food items are manually removed from the lower platen, such as with a flat metal spatula. 
         [0004]    A need exists to remove all of the food items on the lower platen as quickly as possible and preferably all at once to help facilitate production of uniform cooked food products. 
         [0005]    To prevent food items from unwanted adherence to the upper platen, especially when the upper platen is opened when cooking is completed, a PTFE impregnated fiberglass release sheet is mechanically attached to the upper platen. Otherwise, removal of the items is hampered and food item breakage can occur due to sticking, for example. 
         [0006]    Other problems have been linked to food items adhering to the lower platen, including fissures in hamburger patties, for example, commonly referred to as “blow holes.” While not wishing to be bound by theory, it is believed that shrinkage of a 
       FIELD OF THE INVENTION 
       [0007]    The present invention relates to cooking devices and to methods of cooking food items on a grill, griddle or other flat surface. More particularly, the invention relates to devices and methods of cooking food on a flat surface and removing the food therefrom in which removable, disposable, flexible, non-stick sheets are utilized. 
       BACKGROUND OF THE INVENTION 
       [0008]    A need exists for improved devices and methods for cooking relatively large quantities of food, particularly food such as hamburger patties in quick service restaurants. 
         [0009]    Typically, clamshell grills are utilized that have top and bottom (upper and lower) heated cooking platens. The food items to be cooked, typically a plurality of items, such as, for example, 6, 9, 12 or more hamburger patties, are placed on the lower platen. The upper platen is closed onto and in contact with the food items on the lower platen so that both sides of the food items are cooked simultaneously. When cooking is completed, the upper platen is raised and the food items are manually removed from the lower platen, such as with a flat metal spatula. 
         [0010]    A need exists to remove all of the food items on the lower platen as quickly as possible and preferably all at once to help facilitate production of uniform cooked food products. 
         [0011]    To prevent food items from unwanted adherence to the upper platen, especially when the upper platen is opened when cooking is completed, a PTFE impregnated fiberglass release sheet is mechanically attached to the upper platen. Otherwise, removal of the items is hampered and food item breakage can occur due to sticking, for example. 
         [0012]    Other problems have been linked to food items adhering to the lower platen, including fissures in hamburger patties, for example, commonly referred to as “blow holes.” While not wishing to be bound by theory, it is believed that shrinkage of a hamburger patty during cooking, together with adherence to the lower platen surface, results in crack and fissure formation in the meat. Expansion of hot gases trapped between the patty and the lower platen then likely causes these cracks to propagate upward, harming the appearance and integrity of the patty. This problem is exacerbated in high volume cooking, where the time required to remove a full run of patties from a lower platen can result in overcooking of the last patties removed. 
         [0013]    However, the conventional upper platen type of release sheets do not work well on the lower platen. Good sear (good carmelization and browning) on the lower surface of the food items, such as hamburger patties, are prevented when such release sheets are used, making them unacceptable. 
         [0014]    A need therefore exists for a lower horizontal heated platen cooking device that prevents sticking of food items while providing good sear, that is, good carmelization and good browning of food items cooked thereon, such as hamburger patties and other food items. A need also exists for such a device that would also achieve faster removal of cooked food items from the heated lower platen upon completion of cooking. 
       BRIEF SUMMARY OF THE INVENTION 
       [0015]    In accordance with one aspect of the invention, a cooking device is provided that permits efficient cooking of one or more food items. In one aspect, the cooking device comprises a food-supporting cooking platen for supporting food items to be cooked and at least one flexible non-stick release sheet removably laid on top of the food-supporting platen, wherein the release sheet comprises a fiberglass substrate layer having a thin film PTFE layer on each side of the fiberglass substrate. The release sheet has sufficient stiffness to permit removal of food products from the release sheet with a spatula when the release sheet is laid over the food-supporting platen. In addition, when the release sheet is in contact with the platen, an overall heat transfer coefficient from the surface of the food-supporting platen to the food contacting surface of the release sheet is sufficient to achieve good sear on hamburger patties using a food-supporting platen temperature in the range of from about 350-450° F. and more desirably 375-425° F. Typically, such heat transfer coefficients will be at least about 210 BTU/hr-ft 2 -° F. 
         [0016]    Typically, the release sheet will be configured and utilized so that it substantially covers the top surface (the cooking surface) of the food-supporting platen. 
         [0017]    Typically, the thickness of the release sheet will be in the range of from about 0.001 inch to about 0.003 inch and may have a thickness of about 0.002 inch. Typically, the release sheet will be at least substantially liquid-impermeable. This is because it is desirable that no or substantially no liquid from the food products being cooked on the release sheet penetrate through the release sheet into contact with the food-supporting platen surface. The food-supporting platen surface may be the bottom or lower platen of a clamshell-type grill that permits simultaneous two-sided cooking of food products, which may be hamburger patties. 
         [0018]    Typically, the overall heat transfer coefficient when the release sheet is in contact with the food-supporting platen from the surface of the food-supporting platen to the food contacting surface of the release sheet is sufficient to achieve good sear, that is, good carmelization and good browning, on hamburger patties using a food-supporting platen temperature in the range of from about 350-450° F. and more desirably 375-425° F. Typically, such heat transfer coefficients will be in the range of from about 210 BTU/hr-ft 2 -° F. to about 250, 300, 350 or more BTU/hr-ft 2 -° F. Such heat transfer coefficients provide efficient cooking and permit good sear to be achieved on the surface of the food items that are in contact with the release sheet. 
         [0019]    In accordance with another aspect of the invention, an adherence-enhancing fluid is located between the food-supporting platen surface and the bottom surface of the release sheet. It is believed that the adherence-enhancing fluid increases the surface tension between the platen and the release sheet to promote adherence. The adherence-enhancing fluid can be selected from various oils, fats and lubricants, that may be animal, vegetable or synthetically derived, including, for example, without limiting the scope of the invention, cooking oil, shortening, animal fat, oil produced by cooking a food item, or glycerin, for example. Preferably, any such adherence-enhancing fluid will be food compatible. 
         [0020]    In accordance with one aspect of the present invention, commercial methods of efficiently cooking one or a plurality of food items simultaneously are provided. In one aspect, the invention includes providing a platen for supporting food items to be cooked and capable of being heated and a lower platen release sheet as defined herein, optionally applying an adherence-promoting material to the platen and/or the release sheet, placing the release sheet in intimate heat transfer contact with the platen, which may be facilitated through an interface formed by the adherence-enhancing material, if present, placing one or more food items to be cooked directly on the release sheet and cooking the food item(s) in direct contact with the release sheet. Typically, the food-supporting platen will have a heating element associated with it that may be, for example, gas-fired or electrically heated, as desired. Typically, the lower or food-supporting platen release sheet will be in intimate contact with the top surface of the lower or food-supporting platen. The release sheet should have sufficient stiffness to permit removal of food products from the release sheet with a spatula, preferably having a dull edge, when the release sheet is laid over the food-supporting platen, and to stay flat. This is accomplished without the necessity of any mechanical attachment of the release sheet to the lower platen. It is merely necessary to lay the release sheet over the food-supporting platen. If desired, an adherence-promoting material which typically will be in the form of a fluid grease or oil can be applied to the surface of the food-supporting platen or to the bottom surface of the release sheet so that the adherence-promoting material creates an interface between the food-supporting platen and the release sheet placed thereover. Advantageously, when the release sheet is in contact with the food-supporting platen an overall heat transfer coefficient from the surface of the food-supporting platen to the food contacting surface of the release sheet is sufficient to achieve good sear on hamburger patties using a food-supporting platen temperature in the range of from about 350-450° F. and more desirably 375-425° F. Typically, such heat transfer coefficients will be in the range of from about 210 BTU/hr-ft 2 -° F. to about 350 BTU/hr-ft 2 -° F. or greater. Thus, the heat transfer coefficient may be, for example, 250, 300, 350 or greater BTU/hr-ft 2 -° F. 
         [0021]    The flexible, removable, non-stick release sheet may cover substantially the entire top surface of the food-supporting platen. One or more of such release sheets may be utilized to cover substantially the entire cooking surface area of the food-supporting platen. 
         [0022]    When utilized, the adherence-enhancing fluid can be applied to the top surface of the food-supporting platen prior to or while it is heated. Any suitable manner of application of the adherence-enhancing fluid can be utilized including brushing, spraying, roller application, squeegee or other manner of application, for example. It can be advantageous to apply the adherence-enhancing fluid and position the release sheet on the top surface of the food-supporting platen while it is at ambient temperature. 
         [0023]    When cooking is completed, the food item(s) are removed from the food-supporting platen. In this manner, improved intimate heat transfer contact is achieved between the release sheet and the platen, thereby providing more efficient heat transfer between the platen and the food item to be cooked. The food item(s) can be removed from the platen by using a spatula that is inserted above the release sheet and below the food item(s) and manually removed by a human operator, for example. Alternatively, a removal device in accordance with the invention can be used to remove the food item(s) from the lower platen simultaneously. In those simultaneous removal embodiments, the release sheet forms part of a utensil that incorporates the release sheet and has a handle so that a user can grasp the handle and remove the release sheet and the food items from the lower cooking platen simultaneously. The utensils in accordance with the invention include a fork utensil that carries a release sheet and a release sheet-covered hoop utensil. 
         [0024]    The cooking area is defined by the utensil. Specifically, the cooking area for the fork is between two elongated and two spaced apart fork tines. The spacing and area between the two fork tines define the cooking area. For the hoop utensil, the cooking area is defined by the area encircled by the hoop. 
         [0025]    In accordance with another aspect of the invention, a cooking device is provided that comprises a frame defining the cooking area, a handle attached to the frame, the handle extending away from the cooking area and a flexible-non-stick release sheet mounted to the frame, the release sheet covering the cooking area. In one embodiment, the frame is a fork having two spaced-apart tines, each having a length, the spacing between the tines and the length of the tines defining the cooking area. The release sheet may be composed of a sheet having two opposite edges, the ends spaced apart a distance that is about the spacing of the fork tines. The release sheet can be conveniently secured to the fork by inserting the tines into a sleeve that is formed along each of the two side edges of the release sheet. The spacing between the fork tines may be slightly larger than the spacing between the sleeves of the release sheet. By compressing the tines towards each other and inserting the release sheet the tines will exert a spring tension on the release sheet when the release sheet is mounted to the fork tines in that manner. This keeps the release sheet in tension so that there is minimal sag when the fork utensil is lifted from the surface of the food-supporting platen with one or more food items being located on the release sheet. 
         [0026]    In accordance with another aspect of the invention, the frame comprises a hoop-shaped frame that surrounds an area for cooking. The release sheet is attached to the hoop-shaped frame and covers at least substantially the area surrounded by the hoop. The release sheet may be attached to the hoop-shaped frame by forming in situ a sleeve extending peripherally of the release sheet around the hoop-shaped frame. 
         [0027]    The release sheet material for the release sheet utensils can have a thickness typically in the range of from about 0.0002 to about 0.005 inches. The material can be PTFE, a fiberglass substrate that has PTFE applied thereto which can be by, for example, lamination, dipping, impregnating or any other suitable application method. The release sheet material for the utensils in accordance with the present invention need not have the same properties as the release sheet material that is merely laid over the food-supporting platen, particularly since typically a separate spatula will not be used to remove the cooked food items from the utensil release sheet device. Thus, the release sheet for the utensil devices of the invention could be thinner or thicker as desired. If desired, the release sheet material for the utensils in accordance with the invention may be selected so that an overall heat transfer coefficient from the surface of the food-supporting platen to the food contacting surface of the release sheet can be sufficient to achieve good sear on hamburger patties using a food-supporting platen temperature in the range of from about 350-450° F. and more desirably 375-425° F. Typically, such heat transfer coefficients will be in the range of from about 210 to about 350 or more BTU/hr-ft 2 -° F. 
         [0028]    In accordance with another aspect of the present invention, a cooking method is provided. The method includes providing at least one food-supporting platen that can be heated to cook food products placed thereon. The method further includes providing a cooking device comprising a frame that defines a cooking area and further includes a handle attached to the frame. The handle extends away from the cooking area and can optionally be removably attached to the frame. A flexible, non-stick release sheet is mounted to the frame and covers at least substantially all of the cooking area defined by the frame. The method further includes placing a cooking device on top of the heated food-supporting platen and placing at least one food item on the top surface of the release sheet. 
         [0029]    In accordance with the invention, the food items may be placed on the top surface of the release sheet of the cooking device before or after the cooking device is placed on the top surface of the food-supporting platen. Thereafter, the at least one food item is cooked in direct contact with the release sheet while the release sheet is located on top of the heated food-supporting platen. In accordance with the invention, substantially all of the top surface of the food-supporting platen can be covered by the release sheet of the cooking device. In addition, optionally, an adherence-enhancing fluid can be applied to the surface of the heated food-supporting platen or to the lower surface of the release sheet of the cooking device. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0030]      FIG. 1  is a perspective view of a cooking device  10  in accordance with the present invention, having a single heated platen  12  covered with a single full-size release sheet  14 . 
           [0031]      FIG. 2  is a perspective view of a cooking device  16  having a single heated platen  12  covered with a single full-size release sheet  14  and a thin layer of fluid  18  between the platen and release sheet. 
           [0032]      FIG. 3  is a perspective view of a cooking device  20  having a single heated platen  12  covered with a thin layer of fluid  18  and a pair of half-size release sheets  22 . 
           [0033]      FIG. 4  is a front sectional view along line  4 - 4  of  FIG. 2 . 
           [0034]      FIG. 5  is an exploded perspective view of the release sheet  22 , showing an inner fiberglass sheet  26  between two PTFE sheets  28 . 
           [0035]      FIG. 6  is an enlarged fragmentary view of the fiber weave of fiberglass sheet  26  having wider vertical fibers  29  and narrower horizontal fibers  30 . 
           [0036]      FIG. 7  is a perspective view of an open clamshell grill  31  incorporating the release sheets  22  of the present invention. 
           [0037]      FIG. 8  is a perspective view of the closed clamshell grill  31 . 
           [0038]      FIG. 9  is a front sectional view along line  8 - 8  of  FIG. 8 . 
           [0039]      FIG. 10  is a perspective view of a fork utensil  46  in accordance with the present invention. 
           [0040]      FIG. 11  is a perspective view of the fork  54  showing its tines  58  in their relaxed, splayed position. 
           [0041]      FIG. 12  is a perspective view of the fork utensil  46  supporting food items H in an open clamshell grill  60 . 
           [0042]      FIG. 13  is a perspective illustration of clamshell grill  60  closed onto fork utensil  46  to cook food items H. 
           [0043]      FIG. 14  is a front sectional view of the closed clamshell grill  60 . 
           [0044]      FIG. 15  is a perspective view of a hoop utensil  62  bearing a release sheet  64  in accordance with the present invention. 
           [0045]      FIG. 16  is a perspective view of wire hoop  66  and handle  68  with release sheet  64  removed. 
           [0046]      FIG. 17  is a plan view of a release sheet  64  to be hemmed. 
           [0047]      FIG. 18  is an exploded perspective view of an alternative hoop utensil  80  having a removable handle  88  in accordance with the present invention. 
           [0048]      FIG. 19  is a perspective view of the assembled hoop utensil  80 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0049]    Cooking devices and methods in accordance with the invention that can provide easy cleaning and good sear, (as used herein “good sear” means good carmelization and good browning of a food product), browning and cooking of food products, including hamburger patties will be described in conjunction with  FIGS. 1-19 . The figures are not drawn to scale, but rather are intended to illustrate possible arrangements of elements in cooking devices embodying the present invention as will be appreciated by those skilled in the art. 
         [0050]      FIGS. 1-3  illustrate a food-supporting platen cooking device in accordance with the present invention that can be part of a clamshell grill arrangement. Referring to  FIG. 1 , a cooking device  10  having a single food-supporting platen  12  removably covered with a single full-size non-stick, low-friction release sheet  14  is shown. Food-supporting platen  12  typically has a flat cooking surface. Cooking device  10  may be, for example, a single surface griddle or may be the lower platen of a clamshell grill. Any food item H as desired, such as a hamburger patty, sausage, fish fillet, chicken breast, hot dog, pancake, egg, bacon strip, Canadian bacon, mushroom or vegetable, may be placed on release sheet  14  as shown for contact grilling or cooking. 
         [0051]    Release sheet  14  should have sufficient stiffness to permit removal of food products from the release sheet with a spatula and cleaning of the release sheet with a squeegee or cloth when the release sheet is removably laid over food-supporting platen  12 , even when the release sheet is not retained by any mechanical structure. In other words, release sheet  14  merely lays on the surface of food-supporting platen  12 . Additionally, in this embodiment, release sheet  14  in contact with food-supporting platen  12  should have an overall heat transfer coefficient from the platen surface to the food contacting surface of the release sheet of from about 210 BTU/Hr-ft2-° F. including, for example, about 250 BTU/Hr-ft2-° F., about 300 BTU/Hr-ft2-° F., about 350 BTU/Hr-ft2-° F. or greater, and should provide good sear and browning of proteins when the food item H is a proteinaceous food item such as a hamburger patty. Thus, overall heat transfer coefficients of 250, 300, 350 or greater BTU/Hr-ft2-° F. and values therebetween are contemplated. Surprisingly, it has been discovered that a thin release sheet composed of PTFE laminated fiberglass adheres well when laid on top of a horizontal heated platen, provides good sear and browning of proteins, significantly reduces the incidence of fissures in hamburger patties, and does not wrinkle when heated, thus allowing for removal of food items with a spatula without significantly dislodging or disturbing the release sheet and easy cleaning with a squeegee or grill cloth. The PTFE sheets of the invention save significant time and effort by eliminating the need for the laborious scraping required to clean a bare metallic platen and the sharpening of tools used to scrape the platen. Conveniently, release sheet  14  may be simply lifted off of platen  12  to be thoroughly cleaned or discarded and replaced with a clean or a new release sheet  14 . 
         [0052]    Turning to  FIG. 2 , a preferred cooking device  16  having a single heated food-supporting platen  12  covered with a single release sheet  14  and a thin layer of adherence-promoting fluid  18  between the platen and release sheet is shown. It has been found that a layer of an adherence-promoting fluid, which may be ordinary cooking oil, such as sunflower oil or the like, results in even better adherence between a single or lower heated platen and a release sheet laid thereon, providing still easier cleaning as well as better sear and browning. The fluid layer  18  is applied by any suitable method and device including, for example, spraying, brushing or a similar method in an amount ranging from about 1.1 grams/ft 2  to about 18 grams/ft 2 . Any excess oil can be squeegeed from the surface. 
         [0053]      FIG. 3  illustrates another embodiment of the invention in which a portion of a clamshell grill platen cooking device  20  is shown having a heated food-supporting platen  12  covered with a pair of half-size release sheets  22  and a layer of adherence-enhancing fluid  18  between the platen and release sheets. It has been found that smaller release sheets are easier to orient and lay on the platen surface, saving time and effort required for placement of the sheets, particularly for platens that are about 2′ wide×3′ long, for example. Preferably, the sheets should each have an area slightly more than one half that of the heated platen, to provide an overlap area  24 , thus preventing migration of oil from cooking or other undesired material to the platen surface. For example, it has been found that an overlap area about 2 inches wide effectively prevents any migration of unwanted material under the release sheets during a full day of use. 
         [0054]      FIG. 4  is a fragmentary sectional view of a portion of cooking device  20  of  FIG. 3 , illustrating the stacked relationship of a food item H, a release sheet  22 , a layer of fluid  18 , and a single platen  12 . 
         [0055]      FIG. 5  is an exploded perspective view illustrating the layered structure of a preferred form of release sheet  22 . As shown, release sheet  22  is preferably composed of a fiberglass sheet  26  sandwiched between two PTFE sheets  28 . The PTFE sheets may be laminated onto the fiberglass sheet  26 , by means of pressure and/or heat. Release sheet  22  is preferably between about 0.001 and 0.003 inch thick, more preferably between about 0.0016 and 0.0026 in. thick, and still more preferably about 0.0021 in. thick. 
         [0056]    Referring to  FIG. 6 , a greatly enlarged view of a portion of the fiberglass sheet  26  is shown. As seen in the figure, the fiberglass sheet is composed of a woven mesh of wider vertical fibers  29  and narrower horizontal fibers  30 , oriented at right angles, with about 7 fibers per ⅛ inch in each direction, providing numerous void spaces  27 . 
         [0057]      FIG. 7  is a perspective view of the present invention embodied in a clamshell grill  31  having lower and upper heated platens  32  and  34 . As shown, lower platen  32  is covered with a pair of half-size release sheets  22  and a thin layer of fluid  18  in the same manner as the single platen  12  depicted in  FIG. 3 . Upper platen  34  has a handle  31 ′ for conveniently opening and closing upper platen  34  and is covered with an upper release sheet  36  retained in contact with upper platen  34  by dynamic release sheet tensioning system  38 . Dynamic tensioning system  38  is composed of a tapered outer frame  40 , a smaller tapered inner frame  42  nested within outer frame  40 , and springs  44 , secured to pins  44 ′ which provide tension on release sheet  36 . 
         [0058]    Other securing assemblies may also be suitable for use in accordance with the present invention, such as an opposed pair or a plurality of spring-tensioned clips or hooks arranged about the perimeter of the release sheet. Moreover, as alternatives to the dynamic tensioning system  38 , upper release sheet  36  may instead be retained by a heat transfer enhancing adhesive, or in the case of a very thin release sheet, by simply “clinging” to the surface of upper platen  34 . For instance a static charge may be generated on the sheet prior to mounting, thereby creating a static electric cling force that holds the sheet in contact with the platen. 
         [0059]    Turning to  FIGS. 8-9 , clamshell grill  31  is illustrated in its closed position.  FIG. 8  is a perspective view of the closed clamshell grill  31 , and  FIG. 9  is a front sectional view along line  8 - 8  of  FIG. 8 . Optionally but desirably, a heat transfer enhancing material  18  such as a grease, adhesive or fluid may be disposed between upper platen  34  and upper release sheet  36 , as shown in  FIGS. 8 and 9 . 
         [0060]    A cooking device similar to that depicted in  FIG. 9  was tested on cooking hamburger patties, where the release sheets  22  were 0.002-inch thick PTFE-laminated fiberglass sheets available from Saint-Gobain Performance Plastics Corp. under the trade designation Chemfab CF102. CF102 is a PTFE-coated fiberglass having a high content of polytetrafluoroethylene (PTFE) (a resin content of 74 percent), and a smooth surface. CF102 has a weight of 2.80 ounces/square yard, a warp breaking strength of 55 pounds per inch and a fill breaking strength of 50 pounds per inch. Fluid layer  18  was about 2 grams of sunflower oil per square foot applied to the platen by spraying, and upper release sheet  36  was a 0.0045-inch thick PTFE impregnated fiberglass sheet. Lower platen  32  was set at a nominal temperature of 400° F., and upper platen  34  at a nominal temperature of 425° F. Surprisingly, the device was found to provide good sear and browning of the patties, without wrinkling of lower release sheets  22 . It is believed that inner fiberglass sheet  26  prevented wrinkling by providing release sheet  22  with some rigidity. Moreover, another significant unexpected benefit was achieved, namely, the mean temperature variation within the patties cooked was significantly decreased compared to the temperature variation within patties cooked in a clamshell grill having a bare lower platen set at 350° F. 
         [0061]    Without wishing to be bound by theory, it is believed that temperature variation within patties may be caused by the concentration of heat in a heated platen at the locations of a finite number of heaters. The lower platen of the clamshell grill tested had three heaters distributed across a 2 ft×3 ft cooking area. In the aforementioned comparison testing, 0.1 lb. patties cooked in the bare lower platen clamshell grill for about 38 seconds had an observed inner temperature ±3 standard deviation range of 55° F. (standard deviation was 9.1° F.), while 0.1 lb. patties cooked in the grill of the present invention for about 41 seconds had an observed inner temperature ±3 standard deviation range of 29° F. (standard deviation of 4.8° F.), a 53% reduction in internal temperature range. A 30% reduction in temperature range (±3 standard deviation range) was achieved in 0.25 lb. patties, which had a ±3 standard deviation range of 75° F. (standard deviation of 12.5° F. after cooking on the bare lower platen grill for about 104 seconds and only a ±3 standard deviation range of 53° F. (standard deviation of 8.8° F.) after cooking on the grill of the present invention for about 109 seconds. All internal temperature data were taken at various locations in the hamburger patties, all at a patty midpoint depth. Reduced temperature variation in hamburger patties is an important benefit, because many restaurant customers prefer meat that is not overcooked, while a minimum temperature of 155° F. throughout a cooked ground beef food item is required by the FDA Model Food Code. 
         [0062]    Turning to  FIGS. 10-11 , a fork utensil  46  in accordance with the present invention is illustrated. Fork utensil  46  is composed of a release sheet  48  having parallel sleeved ends  50  attached at seams  52  and a fork  54  with a handle  56  and tines  58 . As shown in  FIG. 10 , the tines  58  are inserted into sleeved ends  50 , so that tines  58  define a cooking area A on release sheet  48 . Advantageously, fork utensil  46  may be used to cook a plurality of food items H on a heated platen, simultaneously remove all of the cooked food items and release sheet  48  from the platen, and quickly transfer the food items to another location. Moreover, release sheet  48  is easily removed from fork utensil  46 , and then it may either be cleaned and replaced or discarded and substituted with a new release sheet  48 . This saves time when compared to the laborious scraping and sharpening of utensils associated with cleaning a bare metallic platen, as noted above. 
         [0063]    Tines  58  preferably provide an outward tension T on release sheet  48 , to prevent the release sheet from sagging under the weight of the food items when fork utensil  46  is lifted. In the embodiment illustrated in the figures, this is achieved by providing a fork  54  whose tines  58  are relaxed at a splayed angle, such that they provide outward tension when they are urged into a parallel orientation. Hence,  FIG. 11  illustrates the relaxed, splayed position of tines  58 , which must be urged inwardly before insertion into parallel sleeved ends  50 . Those skilled in the art will recognize that any equivalent manner of providing outward tension in release sheet  48  will also suffice, as long as the tension provided is sufficient to support the weight of a plurality of food items without excessive sagging of the release sheet. Preferably, the fork utensil  46  should support nine 0.1-lb hamburger patties without excessive sagging. 
         [0064]    As tines  58  provide tension to release sheet  48 , stiffness of release sheet  48  is not as important as in the prior embodiments. Accordingly, release sheet  48  may be composed of any suitable non-stick material including a thin film of pure PTFE, as well as a fiberglass sheet laminated, impregnated or dip-coated with PTFE, provided that it will support the weight of a plurality of food items. Preferably, release sheet  48  is between about 0.0002 and about 0.005 inch thick. 
         [0065]      FIGS. 12-14  illustrate a clamshell grill  60  used to cook food items H on fork utensil  46  in accordance with the present invention. Similarly to the clamshell grill embodiments illustrated in previous figures, lower platen  32  is optionally but desirably coated with a layer of adherence enhancing fluid  18  as shown in  FIG. 12 , and fork utensil  46  placed on top of fluid layer  18 . Again, upper release sheet  36  is shown mounted to upper platen  34  by dynamic tensioning system  38 .  FIG. 13  shows clamshell grill  60  in its closed position, and  FIG. 14  is a front sectional view of the closed clamshell grill  60 . 
         [0066]      FIGS. 15-17  illustrate a hoop utensil  62  in accordance with the present invention. As shown in  FIG. 15 , hoop utensil  62  is composed of a peripherally sleeved release sheet  64  mounted to a wire hoop  66  attached to a handle  68 , wire hoop  66  defining a cooking area A′ on the release sheet  64 . Peripheral seam  70  of release sheet  64  extends around substantially the entire periphery of the release sheet, and is interrupted only by a gap  72 . Gap  72  corresponds to the attachment point of handle  68  to wire hoop  66 .  FIG. 16  shows wire hoop  66  and handle  68  without release sheet  64 .  FIG. 17  illustrates how the sleeve in release sheet  64  may be formed. As shown, release sheet  64  is made from a flat square sheet with a square notch  74  cut out. Then, outer attachment region  76  is folded under the sheet to align with inner attachment region  78  as indicated by arrows A-E, and the attachment regions  76  and  78  are joined by any suitable means, such as an adhesive. 
         [0067]    Release sheet  64 , like release sheet  48  used with fork utensil  46 , may be composed of any suitable non-stick material, including a thin film of pure PTFE or a fiberglass sheet laminated, impregnated or dip-coated with PTFE, and is preferably between about 0.0002 and about 0.005 inch thick. 
         [0068]    Referring to  FIGS. 15-19 , similarly to fork utensil  46 , hoop utensil  62  saves significant time and effort when compared to cooking on a bare platen by allowing the simultaneous removal of a plurality of food items and a release sheet  64  on which the food items are cooked, as well as the rapid transfer of the food items to another location. Conveniently, release sheet  64  may be removed and discarded to be substituted with a new release sheet  64 . 
         [0069]    Illustrating an alternative embodiment,  FIGS. 18-19  show a hoop utensil  80  having a peripherally-sleeved release sheet  82  with an uninterrupted seam  84 , wrapped around a wire hoop  86 . Hoop utensil  80  features a removable handle  88 , thus eliminating the need for an interruption in the release sheet seam.  FIG. 18  is an exploded view showing removable handle  88  and attachment assembly  90  separate from wire hoop  86  composed of a bolt  92  and threaded plates  94  to attach handle  88  to hoop  86 . Any suitable attachment configuration can be utilized.  FIG. 19  shows assembled hoop utensil  80 . Conveniently, the easy assembly and disassembly of hoop utensil  80  permits release sheet  82  and wire hoop  86  to be removed and cleaned or discarded as a unit. Then they may be reattached or substituted with a new wire hoop  86  covered by a new release sheet  82 , as desired. 
         [0070]    Food-supporting platens of the present invention are preferably substantially flat, metallic platens of a type widely used in contact grills, such as a clamshell grill typical of the fast food industry. Typically, the platens are stainless steel. 
         [0071]    While the invention has been described with respect to certain preferred embodiments, as will be appreciated by those skilled in the art, it is to be understood that the invention is capable of numerous changes, modifications and rearrangements and such changes, modifications and rearrangements are intended to be covered by the following claims.