Seafood vacuum-pack system
BACKGROUND OF INVENTION 
     1. Field of Invention 
     The present invention relates to a method of vacuum packing frozen seafood and more particularly to a method of and apparatus for vacuum packing frozen peeled shrimp, cooked or uncooked, and the like to produce, for example, even microwave cooking, and an apparatus therefor which includes forming means for forming the packet for the seafood with a smaller thickness in its central area in comparison to its peripheral areas, and further to the resulting pack therefrom. 
     2. Prior Art &amp; General Background 
     With respect to food technology generally, it is well known to provide vacuum packed food in packets or pouches for defrosting and cooking of the frozen food in boiling water or in a microwave. In such packing, the packed food is contained in a transparent plastic package made of barrier film, i.e. a film which holds a vacuum and does not &#34;breathe,&#34; and the food, while still in its package, is cooked or at least defrosted. Classic examples of such food packaging for immediate home use in for example a microwave oven are the food packages provided by Stouffer&#39;s. 
     In the commercial packaging of such food products, the packs are formed on a continuous, mass production basis, in which upper and lower barrier films are provided with the food placed between them on the lower film, and the individual packets evacuated and sealed and separated. Machines which are used for such packing are called &#34;form, fill and seal&#34; machines. 
     However, in attempting to apply such technology to the packing of for example frozen, peeled shrimp, which is a highly heat sensitive food product, it was found that such technology did not work, and the end food product, when cooked or defrosted in the package, was heated unevenly. In particular, the shrimp located in the center were under cooked or heated, while on the other hand the shrimp at the peripheral edges were over cooked or heated, by the microwave unit. As a result, such technology has not heretofore been available for products such as shrimp. 
     One of the problems noted by the inventor was that such machines tended to cause the shrimp to be relatively bunched up in the center of the package in the final sealing step. 
     General, Summary Discussion of the Invention 
     The present invention overcomes this prior art problem by providing a system which is highly reliable, relatively economical and very cost effective, in which the shrimp or other like food product is packed in the plastic container with a lesser density in the central area and a greater density in the peripheral areas, preferably with a smooth, curved transition in densities between the extremities. 
     In the preferred embodiment this pack is produced by forming the bottom pouch film layer with a raised portion in its center flowing out to a maximum thickness at at least two of its opposed peripheral edges. Such a forming of the pouch can be created by placing the bottom film layer on a form, which is for example either spherically or curvi-linearly shaped, the latter being made for example from a cylindrical section. The resulting pack then has a greater number of shrimp and hence a greater density at its peripheral areas and a lesser number and hence a lesser density at its center. 
     Thereafter, when the frozen shrimp pack is placed in a microwave and heated, the resulting food product comes out relatively evenly cooked throughout, producing a very tasty, convenient food product for the consumer. 
     Although the invention has been found to be particularly effective for shrimp, the principles thereof could be applied to other food products, particularly those which are highly heat sensitive, such as for example seafood, and which are packed in a manner that the contents are subject to be rearranged and spread out with respect to itself and hence fungible. For example a typical, rectangular shrimp pack of for example five inch by six inch size (when viewed in its lateral extent from a top perspective) might contain approximately twenty to sixty individual shrimp, allowing the contents to be moved about to produce the varying densities in the pack taught in the present invention. Other exemplary seafood products would include crawfish, minced fish, small fish (e.g. sardines), crab meat, oysters, etc. 
     It is thus a basic object of the present invention to provide a vacuum packed food pack of highly heat sensitive frozen food product(s) which has a lesser food density in its central area in comparison to its surrounding areas, to produce an evenly heated product when heated in for example a microwave oven, an exemplary food product being frozen, peeled shrimp. 
    
    
     BRIEF DESCRIPTION of the DRAWINGS 
     For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals, and wherein: 
     FIG. 1 is a side view of an exemplary, prior art vacuum packed, frozen food pack with variation(s) thereof being shown in phantom line. 
     FIG. 2 is a side view of the preferred embodiment of the varying density, vacuum packed, frozen food pack of the present invention, similar in perspective to that of FIG. 1, for comparison purposes. 
     FIG. 3 is a simplified, flow chart or schematic type view showing the three stages of an exemplary &#34;form, fill and seal&#34; machine incorporating the bottom forming techniques and forms of the present invention, used to produce the packet configuration of FIG. 2. 
     FIG. 4 is a top perspective view of a first, exemplary, curvi-linear embodiment of a form which can be used in the machine of FIG. 3 to form a curved bottom in the packet; while 
     FIGS. 5A &amp; B are top and side views, respectively, of a second, exemplary, hemispheric embodiment of a form which can be used in the machine of FIG. 3 to form a curved bottom in the packet. 
    
    
     DETAILED DESCRIPTION of the PREFERRED, EXEMPLARY EMBODIMENT(S) 
     As can be seen in FIG. 1, a typical, exemplary, vacuum packed frozen food pouch or packet 1 ideally (in prior art terms) contains an evenly distributed food product having a rectangular, side cross-section, as illustrated in solid line in the drawing. However, in fact, the &#34;form, fill and seal&#34; machines used often produce a packet 1&#39; having in side configuration a convexly curved, thicker depth in its central region 1C&#39;. This is caused by the action of the bottom and/or the top film layer(s) B &amp; T, respectively, pushing the contained food in toward the center during the vacuum sealing stages as the film(s) shrink inward. 
     Such a prior art pack, although apparently fine for most food products, causes an unacceptable, unevenness of heating of the product, when used for a highly heat sensitive food product such as for example frozen, peeled shrimp. For example, the heat sensitive food will be overly cooked or heated at the peripheral area 1P, in comparison to the insufficiently heated or cooked central, thicker area 1C. 
     In contrast, with reference to FIG. 2, the preferred, exemplary food pack 10 produced in the present invention has a smaller, less thick dimension in its central area 10C, in comparison to the larger, thicker, peripheral or surrounding areas 10P. Preferably, as illustrated, there is a smooth, curved progression of varying thicknesses from the central area 10C to the outer, surrounding, peripheral areas 10P, at least with respect to two, opposed edges. 
     Such a pack 10 has a higher density of container food F at the peripheral areas 10P, in comparison to the central area 10C. Thus, for example, in the preferred, exemplary application of frozen, peeled shrimp (cooker or uncooked), there are a greater number of shrimp one above the other in the peripheral areas 10P, than in the central area 10C. 
     An exemplary shrimp pack having a size of approximately five inches by six inches could have a count of approximately twenty to sixty shrimp, with the central portion 10C having a thickness of about three-eights of an inch and with the peripheral, maximum thickness portion 10P having a thickness of about five-eights of an inch, although of course these particular dimensions are subject to great variation. 
     With reference to FIG. 3, this contoured package 10 for example could be produced by including a rigid form 20, preferably convexly curved, in at least the sealing structure 50 underneath the lower or bottom layer B of the barrier film forming the ultimate pouch or packet 10. This then causes the shrimp or other food product to be properly distributed when sealed in the desired density distribution described above, during the evacuation and sealing steps. Once so sealed, the package 10 maintains its density distribution under the tautness of the sealed top and bottom film layers T &amp; B. 
     It is noted that in the sealing station 50 the area between the film layers T &amp; B is evacuated and the peripheral edges surrounding each pack are sealed together, producing the relatively flat surrounding peripheral strip 11. Usually more than one pack, for example a grouping of four or six or eight packs, is processed in the sealing station 50 at a time. A form 20 is included at the underside of each pack located centrally underneath it. Exemplary &#34;form, fill and seal&#34; machines are marketed under the brand name &#34;TIROMAT&#34; and also by the Mahaffy &amp; Harder Company. 
     If desired, such rigid forms 20 could also be included in the forming or form station 30, as illustrated, in order to pre-form the concavity of the bottom layer B of the film, before the food product is added at the subsequent fill station 40. Such inclusion further insures that the desired density distribution of the ultimately packaged product will result. 
     Two exemplary embodiments 20A &amp; 20B for the rigid form(s) 20 are illustrated in FIGS. 4 and 5A &amp; 5B, respectively. 
     As seen in FIG. 4, the first exemplary embodiment 20A is made of a longitudinally extended, rigid plate bent along its centerline presenting a curvi-linear, convex surface on its upper side. Alternatively, a curved, cylindrical section could be used. When placed under the bottom layer B of the barrier film, it causes the flexible film to be bowed up in its central area to produce the reduced center portion 10C and relatively downwardly flared, peripheral portions 10P at two of its opposed peripheral edges. If desired, such a longitudinally extended form 20A could be extended in one or more sections to effectively reach all the way through the filling station 40 to and within the final sealing station 50, so that the center portion of the bottom film layer B is always supported in its centrally bowed up configuration throughout the machine. 
     As seen in FIGS. 5A (top view) &amp; 5B (side view), the second exemplary embodiment 20B is made of a rigid, hemispherical section or at least a &#34;flatten,&#34; near &#34;hemispherical&#34; section, both of which present a fully curved, convex surface on their upper sides. When placed under the bottom layer B of the barrier film, the form 20B causes the film to be bowed up in its central area to produce the reduced center portion 10C and relatively downwardly, peripheral portions 10B at all four of its opposed peripheral edges. 
     Such rigid forms 20 are necessary when the packing material for the pouches is in the form of flexible, non-rigid film. However, if the material is provided in the form of a relatively, form-holding material, the bowed bottom (and/or top) could be pre-formed independently of the packaging machine to produce the desired density varying distribution result described above with reference to FIG. 2. 
     Although for illustrative purposes the bowing in the foregoing embodiments was always on the bottom film layer B, alternatively or conjunctively the top film layer T could be bowed downwardly or inwardly, the primary goal being the desired density distribution of less in the center and more in the surrounding areas up to and including the very peripheral edges for the contained or packaged food product. 
     After the packed frozen shrimp leave the sealing station 50, they are ultimately provided to the consumer for eating when desired. When such is desired, the consumer merely places the packet 10 in the micro-wave, and, for pre-cooked shrimp, the packet is defrosted or thawed in the micro-wave in approximately an exemplary one minute. For frozen, non-cooked shrimp, the packet 10 is cooked in the micro-wave for an exemplary three to four minutes. 
     It is noted that the drawings have been somewhat simplified for illustrative purposes and the nicely defined perfectly curved line for the underside of the packet 10 is not absolutely necessary. Indeed, in reality the film will tend to cling up and around the enclosed food items, such as for example the rounded bodies of the shrimp, but of course the package will still have the desired distribution of more shrimp one above the other at the peripheral edges 10P that in the center 10C. 
     The embodiments described herein in detail for exemplary purposes are of course subject to many different variations in structure, design, application and methodology. Because many varying and different embodiments may be made within the scope of the inventive concept(s) herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirements of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.