PACKAGING PERISHABLE LIQUIDS IN GABLE TOP CARTONS

Abstract: The invention relates to the shelf stable packaging of perishable liquid food products in hermetically sealed gable top cartons (13) rendered easily openable to the user. The carton is rendered easy to open by sealing it with patterned jaws (Fig. 7, 9, 10, 11 and 12) which apply sufficient pressure to achieve a strong seal along a horizontal stake line (22), vertical stake lines (21 and 21a) and a center stake point (70). The center stake point (70) being optionally located close to the upper edge of the end flaps (20) so as to leave the area (26) of the intersection of the end flaps (20) and side flaps (19) at the horizontal fold line (27) substantially unsealed. A suitable jaw (Fig. 11) for rendering the carton easy to open includes a horizontal rib (43) to form a horizontal stake line, at least one vertical rib (44) to form a vertical stake line and a center stake (471) located to provide a center stake point immediately below the upper edge of the end flaps (20) at the gap (29) but well above area (26).

Description: PACKAGING PERISHABLE LIQUIDS IN GABLE TOP CARTONS TECHNICAL FIELD This invention relates to the shelf stable packaging of perishable juices and other perishable liquid products in hermetically sealed gable top cartons acceptable to the consumer. A packaged product is said to be shelf stable when it retains its desirable qualities for an extended period of time without refrigeration. Being acceptable to the consumer means that the carton is easy to open. BACKGROUND ART The selection of appropriate containers and processes for packaging a particular liquid food product presents the packer with various options from which to choose. Against these must be considered numerous factors. These include cost of the container and packaging process, structural integrity and weight of the package, handling convenience for the packer and convenience for the consumer i.e. , can the container be tightly packed? Is it fragile? Is it openable and resealable? The packer must also con¬ sider the distribution network and infrastructure available in the market sought to be served: is refrigeration avail¬ able, if not, the packaged product must be rendered shelf stable? A package which is too costly in relation to the value of the product itself or which is inconvenient in some respect for the consumer will meet with market resistance and likely fail to win a sufficient degree of acceptance to be commercially viable. Traditionally juices have been packed in cans and glass bottles. The technology applicable to these packages is well known. Juices packed in these containers may be kept unrefrigerated for extended periods provided that these products and their containers have been sterilized and hermetically sealed in order to prevent entry of bacteria. These containers have achieved wide acceptance through use. They may be easily sterilized and sealed effectively. They tolerate both internal vacuum and positive pressure. Closures such as twist off lids for bottles are acceptable to consumers because they are easy to operate and may be used to close the bottles effectively after first opening. These containers resist high temperatures and thus may be sterilized at usual temperatures without deteriorating their structural qualities. Among the disadvantages of glass bottles and cans are cost and the weight which they add to the pro¬ duct. Also, because of their shape, cans and bottles cannot be tightly packed. In the case of bottles their relative fragility is also a disadvantage. More recently greater use of so-called flexible containers has been made for the packaging of liquid food products. These include paper-based containers, molded plastic containers and plastic pouches. Two types of paper-based flexible containers have become widely accepted, the gable top carton and the brick pack. The gable top carton has been extensively used for packaging refrigerated non-shelf stable liquid products such as milk and other dairy products and fruit juice products. The brick pack, so called because of its shape, has been extensively used in association with an aseptic packing process for liquid foods such as fruit juices, milks, sauces, etc. packaged for shelf stability and which therefore do not require refrigeration. The gable top carton is relatively inexpensive and light weight. Moreover, because of its planar sides it can be tightly packed for shipping and storage. The gable top carton enjoys wide acceptance in the public for its ease of storage and handling after opening and for its spout which pours well and re-closes effectively even to the extent of permitting the contents to be lightly shaken with¬ out spilling. One disadvantage of the gable top carton, when compared with glass bottles, is the difficulty encountered by many consumers in opening the carton for the first time. This problem has been largely overcome in the dairy and fruit juice industry by simply weakening the seal at the spout. A previously proposed method of weakening the spout is described in U.S. Patent No. 3,116,002, wherein it is suggested that a non-adherent material " adhesive" be applied to selected areas near the spout in order to reduce the plastic-to- plastic bond formed during the sealing process. This method adds to the cost of the carton and quality control as to the precise placement of the abhesive is difficult to achieve during packing. While the otherwise desirable goal of achieving a strong hermetic seal is defeated the consumer has become accustomed to the fact that dairy products and juices packed in this way must be kept refrigerated and have only limited shelf lives. Because of this practice of weakening the seal to please the consumer, from a consumer acceptance point of view, it is not possible to successfully market a juice in a gable top carton unless the spout is relatively easy to open. Unfortunately, in some ways the gable top carton lacks the structural integrity of other containers, especially cans. for instance, gable top cartons are relatively intolerant of internal vacuum or pressure. Also their physical properties make them less tolerant of high sterilization temperatures. As discussed below, these drawbacks have inhibited use of gable top cartons in shelf stable packaging. Typically, gable top cartons are formed of paperboard sheet material having an overall coating of thermoplastic film such as polyethylene applied on the surfaces of the sheet. The plastic coated paperboard is impervious to moisture and is particularly suitable for use in packaging products such as milk and orange juice. The thermoplastic coating not only serves to moisture proof the carton but also can be utilized for sealing the carton closing flaps which characterize the gable top carton. This sealing action is accomplished by heating the surfaces to be sealed while pressing them tightly together to form a liquid tight plastic-to- plastic bond. The carton erected from the plastic-coated blank typically includes a bottom, four sidewalls extending from the bottom and " united along their lateral margins, and an upper closure means which can be opened to form a spout. The closure is formed from four end wall portions united with the sidewalls and with each other at the lateral margins; the end wall portions are inclined in pairs toward each other and have marginal portions heat sealed to each other which form extensions of the end wall portions; the marginal portions of two opposite end wall portions are folded like bellows between the outer marginal portions of the two remaining end wall portions and at least one of the two inwardly folded marginal portions is move able outward together with the pertaining end wall portions from its position between the two outer marginal portions to a new position outside these where the marginal portion after being moved outward, as well as its pertaining end wall portion, form a pouring spout and an emptying passage. Traditionally, dairy products and fruit juices packed in gable top cartons have been kept refrigerated throughout the distribution process in order to avoid almost immediate spoilage. This spoilage would result from the fact that the gable top cartons are not sterilized and that bacteria in the environment and on the inside of the carton itself would develop very quickly. It is only refrigeration which retards spoilage for up to a few of weeks. Products packed in this way are not said to be shelf stable. Shelf stability is extremely desirable from many standpoints. A shelf stable product is much less likely to spoil while in the distribution system and with a shelf life measured in months rather than days losses due to spoilage should be low. The packer does not need to maintain the product under refrigeration either in its warehouse or while in transport. Similarly the retailer need not allocate expensive refrigerated space to store its supply of product. The consumer also has the advantage of a product which does not require refrigeration until opened. Shelf stability may only be achieved in two ways. First, use may be made of chemical preservatives. Alternatively, precautions must be taken to exclude the possibility of bacteria coming into contact with the product following pasteurization of the product itself. In order to achieve shelf stability of a juice or similar liquid food product without using chemical preservatives the product must be sterilized (said to be pasteurized) . Following pasteurization no bacteria must be permitted to come into contact with the product. To ensure that this is the case, all bacteria which may come into contact with the product prior to or at the time of filling and sealing of the carton, all bacteria within the carton and all bacteria in the environment which becomes trapped in the carton after sealing must be killed. Failure to do so will inevitably lead to spoilage. With glass containers and cans a process known as post packaging sterilization has been employed to achieve shelf stability. The liquid is poured into a non- sterile container, the container is capped and sealed; the container and its contents are heated to and maintained at a sterilization temperature until all the bacteria within the container are killed; the container is then cooled; the product is then shelf stable. This process has been used in the brewing and soft drink trade in packaging liquids in bottles and cans. It has also been used to package liquids in flexible containers. For example, U.S. patents 4,088,444 to Byrne and 2, 995,418 to Muller each disclose a sterilization process wherein a container formed from flexible material such as plastic is fiHed with a liquid, sealed, and sterilized by first subjecting the container to a hot liquid bath or to steam until the temperature of the liquid in the containers reaches the sterilization temperature, maintaining the temperature at the sterilization temperature until steriliza¬ tion is effected, and thereafter cooling the liquid in the containers by subjecting the containers to cold water. Muller in particular specifically contemplates sterilizing fruit juices which are in sealed plastic containers. U.S. patent 4,376,126 to Evers discloses a method of making a yogurt beverage which includes the steps of pasteuri ation or sterilization after the beverage has been packed in a container. Evers, however, does not appear to specifically disclose the use of any particular container nor does he mention the special problems associated with gable top cartons. U.S. patents 4,057,391 to Yamaguchi, 3,481, 688 to Craig et al. and 2,380,134 to Waters disclose methods of preserving or sterilizing food in flexible containers, such as plastic containers, whereby the food is subjected to heating and then cooling after being sealed in the con¬ tainers. However, these patents do not specifically teach the sterilization of liquid food products, such as fruit juices nor do they address the special problems associated with gable top cartons. U.S. patent 237,449 to Schaumberg et al. dis¬ closes a method of preserving fruit juices in glass bottles that includes bottling and sealing the juices and thereafter heating the juices to 170 F for 35 minutes. However, Schaumberg et al. does not disclose subjecting the heated bottles to a cooling process and does not contemplate the use of plastic or plastic coated cartons nor does he address the special problems of gable cartons. Despite the wide recognition of the usefulness of most package sterilization in other packaging systems, the process has not to the inventor's knowledge previously been used to package perishable liquids in gable top cartons. Since the introduction in the 1950 * s of paper- based cartons for liquid food products, only two processes have been widely promoted in order to permit paper-based cartons to be used for packaging shelf stable products. These are the aseptic process, promoted since the early 1960 's by Tetr Pak of Sweden principally in association with the so-called brick pack, and the hot fill process more recently adapted for gable top cartons from a process used in connection with glass bottles. In accordance with the aseptic process the product is pasteurized and kept in a sterile environment up to and through the filling and sealing of the container which is pre-sterilized ( generally using hydrogen peroxide and steam) and also kept in a sterile environment until filling and sealing. The seal must be hermetic under all conditions. Aseptically processed brick packs must be cut, pierced or torn to open. In each case either the opening or the re-closing is clumsy and is not considered advantageous from a consumer convenience point of view. The aseptic method is complicated to carry out and requires specialized and expensive equipment and maintenance. Notwithstanding the complexity and cost of the aseptic process it became widely accepted in Europe, Australia and Canada in the 1970 's. It was only approved in the United States in the early 1980 's and has become widely accepted since that time. Prior to the introduction of the aseptic process and the brick pack there were no shelf stable products packaged in paper-based containers. The aseptically packed brick pack created a whole new application for paper-based containers. The success of the aseptically packed brick pack has been nothing short of phenomenal. It is estimated that, on a worldwide basis, aseptically packed brick packs account for over $20 billion dollars worth of liquid food products. Because of the complexity and cost of the aseptic process, efforts were made to achieve shelf stability in paper-based containers, most desirably with the popular gable top carton, with simpler less expensive technology. In the early 1980 's a so called hot fill process was pro¬ posed. The hot fill method, a less costly alternative to the aseptic method, did not meet with much success. In accordance with the hot fill method the pasteurized product is heated to temperatures in the range of 185 degrees F and poured hot directly into the gable top carton which is then sealed. The heat of the product itself kills the bacteria remaining within the container after sealing. In the United States the hot fill method for gable cartons was adopted by various juice packers but has largely been abandoned because this method results in a substantial vacuum being created within the container following the cooling of the product from the hot fill temperature to room temperature. This vacuum is undesirable because it promotes the inflow of bacteria from the environment through the seal which leads to quick spoilage unless the product is refrigerated. In order to deal with this problem the seal must be strong enough to withstand the significant pressure differential created by the process. The seal must also be strong enough to retain its integrity in all cases throughout the distribution process. If at any time seal integrity is lost, the vacuum will cause bacteria to enter the carton and virtually immediate spoilage to occur. Where the seal was made sufficiently strong to prevent the entry of bacteria under all conditions, the cartons were so hard to open that consumers, used to the ease of opening of the weakly sealed gable cartons used for dairy products, resisted the container. In practice, the strength of the seal which had to be provided to overcome the problems created by the high vacuum resulted in a significant percentage of the cartons not being readily openable by the consumer in the ordinary way. This was such a problem that International Paper, the principal proponent of the hot fill technology, developed an alternative form of opening the carton, subject of US patent No. 4,527,732 issued in 1985, which covers a scored "smile" to be pushed through by the consumer. Gable top cartons have also been constructed with a plastic cap sticking out of a roof panel of the carton. Thus up until the present invention industry efforts to adapt the popular gable top carton to achieve shelf stability and yet retain its good opening and hand¬ ling qualities all at reasonable cost have heretofore not proven successful; and this despite the fact that finding an uncomplicated and inexpensive method of achieving shelf stability with a gable top carton would open up a market worth at least several hundred million dollars for cartons alone. Thus, there remains a need for a system for shelf stable packaging of perishable liquids which allows use of a gable top carton which can be hermetically sealed to ensure shelf stability while retaining an easily opened spout necessary for consumer acceptance. DISCLOSURE OF INVENTION The present invention overcomes the difficulties referred to above in adapting the gable top carton for the packaging of shelf stable liquid products such as juices in a manner acceptable to the consumer. The present invention is, to some extent, the consequence of the present inventor's recognition of a significant inter¬ relationship between the strength of seal necessary to maintain hermeticity and the process used to sterilize the gable top carton. Having recognized this, the present inventor has determined that the lack of a commercially viable system for shelf stable packaging in gable top cartons is primarily due to a failure to find an acceptable compromise between hermetically sealing and ease of opening of the sealed spout of the gable top carton. These two objectives are diametrically opposed; the stronger the seal, the harder it is to open and the lesser the consumer acceptance. The present inventor has discovered that shelf stability with a weakened seal on the gable top carton can be achieved through the selection of an appropriate post- pasturization process combined with an appropriate seal design. A weakened seal can be used because no vacuum is created in the inventor' s process otherwise a much tighter or more hermetic seal would be required. The inventor has also discovered that an adequate seal which is still easy to open can be achieved by applying increased pressure at certain empirically located critical points along the seal. If these critical points are adequately sealed, the remainder of the seal can be sealed in an easy open fashion. Other methods such as abhesives could be used but the above method is preferred. Consequently, the spout is still easy to open. Of course, sealing at these critical points may not only be achieved with sealing jaws which apply pres¬ sure at these points, but also by other methods such as selective heating of the seal area in an appropriate pattern by the use of a laser for example. In summary, the inventor has discovered a technique for achieving the shelf stable packaging of perishable liquids in a gable top carton which is easy to open. The technique involves the combination of a technique for sealing a liquid in a gable top carton and a process for sterilizing the interior and contents of the sealed carton. All of which is possible because no vacuum is created. In accordance with the present invention, the liquid food product to be packed is first pasteurized, if required, in accordance with procedures appropriate to particular product. The product is then cooled to room temperature (i.e. between 60 - 80 F) and introduced into gable top cartons which are then satisfactorily hermetically sealed at the empirically determined critical points along the sealing portion of the gable top carton as described below in such a way as to permit their ease of opening for the consumer. As mentioned before there are other methods which could be used but are less adequate. The filling process is open to the environment. In order that the gable carton be rendered easy to open it is hermetically sealed more securely over certain predetermined portions of the sealing flaps than over others. The predetermined portions of the sealing flaps include: a) a horizontal stake line extending the full length of the side flaps at a level just above the upper edge of the end flaps; b) at least one vertical stake line located inwardly of each end of the flaps extending downward from the horizontal stake line to the horizontal fold line; c) a center stake of a size and shape sufficient to cover portions of both of the end flaps and being located between the horizontal stake line and the horizontal fold line and preferrably being located above a point mid-way between the upper edge of the end flaps and the horizontal fold line. This seal may be achieved with conventional heat sealing equipment using pressure jaws patterned to apply greater pressure over these predetermined areas than over the remaining areas of the seal. The same result may be achieved using planar or unpatterned jaws provided the thermoplastic in the seal area is specifically heated, for example by laser, in a pattern to achieve a strong seal in these predetermined areas. An abhesive may also be used to create such a pattern by applying it over each area of the seal except those predetermined areas. Of course while this sealing technique is applicable when shelf stability in a gable carton is desired it may also be used effectively for products not marketed for shelf stability such as is often the case for milk if it is desired to render the carton easy to open and yet sufficiently sealed to prevent leaks. The sealed cartons are then heated to and held for an appropriate time at a post-pasteurization temperature appropriate to kill the environmental bacteria, mold and yeast remaining within the product and within the carton but at a temperature below that which would melt the inner plastic layer of the carton or cause delamination of the carton. Generally a post-pasteurization temperature in the range of about 160 F is appropriate with a preferred temperature of about 167 F with a holding time of about 10 minutes. The cartons are then cooled. Because the contents were originally sealed in the carton at room temperature and returns to room temperature after being heated, no vacuum is created (i.e. no pressure differential across the seal) and thus there is no danger that environmental bacteria will be drawn into the carton in the event the integrity of the seal is sub¬ sequently lost. While the seal is hermetic, it need not be as strong as that required if the hot fill process were used and is therefore more acceptable to the consumer because the carton remains easy to open. The present invention offers significant advantages over the hot fill method. With the present invention the desirable easy opening characteristics of the gable top carton may be retained which is not possible with the hot fill method because the seal must be very strong in order to overcome the pressure differential across the seal created by that process. In the event that seal integrity is lost or a leak occurs in a container packed by the hot fill method, the internal vacuum will immediately draw harmful micro¬ organisms into the container which will lead to spoilage. With the present invention, because there is no vacuum in the head space above the liquid in the carton, a minor break in the seal or leak elsewhere will not result in microorganisms being drawn into the carton and thus spoilage will be avoided. As compared with the aseptic process, the present invention requires much less sophisticated equipment which is both less costly and easier to operate. It is estimated that, taking into account capital costs and operating costs, the present invention can be worked for approximately 50% of the cost of the aseptic process in operations of a certain size. The present invention is also more secure than the aseptic process. Packing in the aseptic process must be done in an entirely aseptic environment. If, because of equipment or operator problems, any bacteria should find its way into the product or the container after they have been separately sterilized and before the package is sealed, then spoilage will occur. The present invention permits the fill ing to be done in an open environment because the bacteria is killed after the package is sealed and no further opportunity for bacteria to enter the carton occurs . Another advantage of. the present invention over the aseptic process is that the present invention does not require a steril izing agent such as hydrogen peroxide. With the aseptic process it is always possible that traces of hydrogen peroxide rem ain on the inside surface of the container and contaminate the product. The use of hydrogen peroxide also presents a problem for workers packing the product. If for any reason the ventilation system required to evacuate hydrogen peroxide vapours should not operate properly, the atmosphere in the packing area may very quickly become contaminated and pose a health hazard to the workers. The present invention presents no such danger. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view of a conventional gable top carton having an arrangement in a closed state; FIG. 2 is a perspective view of the package of FIG. 1 in an open state; FIG. 3 shows part of a blank for making a gable top carton; FIG. 4 is a perspective view of a gable top carton according to the present invention; FIG. 5 shows the carton of FIG. 4 partially opened; FIG. 6 shows the carton of FIGS 4 and 5 opened up to show the heat sealed areas. FIG. 7 is a view of a die used to seal the carton of FIGS. 4 and 5. FIG. 8 is a perspective view of a gable top carton in accordance with another embodiment of this invention illustrating the opening of the carton; FIG. 9 is a perspective side elevation view of the female portion of a die for producing the embodiment of FIG. 8; and FIG. 10 is a perspective side elevation view of the male portion of a die for producing the embodiment of FIG. 8. FIG. 11 is a perspective view of an improved male jaw for sealing a gable top carton; FIG. 12 is a perspective view of an improved female jaw for sealing a gable top carton; FIG. 13 is a cut-away view of a gable top carton; FIG. 14 is a side view of the top of a gable top carton. MODES FOR CARRYING OUR THE INVENTION FIGS. 1-3 show a conventional gable top carton construction. The package shown in the drawings has four side walls 1 and a bottom ( not shown) . Furthermore, the package has four end wall portions 2 which are united on one hand with the sidewalls 1 and on the other with each other. At the upper free margin, the end wall portions 2 are provided with marginal portions 3 and 4 which are folded toward each other in such a way that opposite end wall portions 2 are inclined in pairs toward each other and that the marginal portions 3 of two opposite end wall, portions lie folded like bellows between the marginal portions 4 of the two remaining end wall portions. Thus, the end wall portions 2 which are provided with the inwardly folded marginal portions 3, will, as shown in FIG. 3, be divided into three essentially triangular portions, the intermediate one 5 of which extends between the end wall portions 2 provided with the outer marginal portions 4, while the two side portions 6 rest against the inside of each of each one of these. The gable top carton is constructed from sheets of material which include at least a basic outer layer of cardboard and an inner layer of thermoplastic material. Normally, the sheet is entirely plastic coated and can include additional barrier layers. The preferred structural material of the present invention is in five layers, namely, an inner coating of polyethylene and aluminum (or other satisfactory barrier material) barrier, another polymeric layer to bond the foil, a layer of paper board and an outer layer of polyethylene or lacquer. A sixth layer, usual for hot filling methods, is not needed with the present invention. Suitable plastics for the carton also include vinyl resins, such as polyvinyl chloride, regenerated cellulose, polypropylene, polyethylene tere- phalate, polycarbonates and other plastics that are used for food products. Where a barrier layer is to be used, ethyl vinyl alcohol or like barrier film may be substituted for foil. The sealing of the package with the marginal and end wall portions in the position shown and described is brought about by means of heat, which will fuse the thermoplastic layers with the sealing zone. When the package is to be opened, the seal is torn open over one half of the sealing zone, whereupon the inwardly folded marginal portion located in said zone is pulled out to the position shown in FIG. 2, where the marginal and the end wall portions will form a pouring spout. FIG. 3 shows part of a blank for a package of the indicated kind. The drawing shows essentially only that part of the blank which is to form the inside surface of the marginal and end wall portion of the package, which can be opened. The blank is provided with fold or score lines along which the blank is to be folded as to form the finished package. Referring now to FIGS. 4 and 6, the carton illustrated is mainly of conventional construction. It includes opposed pairs of side walls 10 and 11, connected by a fifth panel 12. There is a bottom closure 13 and a gable top generally indicated at 14. The gable top includes a pair of side panels 15 having fold or score lines 16 to facilitate opening and a pair of end panels 17 having fold or score lines 18. A pair of top or side flaps 19 are extensions of side panels 15 and extend somewhat higher than end flaps 20 that are an extension of end panels 17 , Side flaps 19 are heat sealed in face to face relationship as shown. Flaps 19 and 20 splay at horizontal fold line 27 to form the top of the carton. End flaps 20 are heat sealed to the interior of the lower parts of side flaps 19 as shown in FIG. 5. Both in the case of hot fill and for non-shelf stable packed juices and dairy products flaps 19 and 20 are sealed over their entire surfaces. It is also known to provide further additional optional sealing such as a pair of vertical stake lines 21 at the end that is not to be opened and which coincides with the fifth panel 12. Optionally, at the other end there is stake line 21a. There may also be a horizontal stake line 22 extending across the side flaps 19. Stake lines are strongly indented to give a more secure seal. There may also be a center stake point 70 which presses together, expands into abutment and seals the adjacent edges of the inwardly folded end flaps 20. The foregoing is conventional structure. The present inventor has discovered that, in combination with an appropriate post-pasturi ation process, the said optional sealing areas are the truly critical ones. If these are made then it is not necessary to seal flaps 19 and 20 uniformly over their entire surfaces . Having realized this the present inventor empirically discovered what specific areas other than the critical areas should be sealed and the extent of such seal in order to achieve the desired easy opening characteristic in a shelf stable gable top carton. Since sealing at the critical areas is sufficient to ensure that, in combination with the post- pasturization process selected, the seal will in a commercially acceptable percentage of cases keep bacteria out of the carton, the non-critical areas, i.e. , the areas which are not staked, can be selectively sealed lightly or not at all to make the carton easy to open. One such construction is shown in FIGS. 4-6. The difference from conventional structure according to this embodiment is in the area of the seal between side flap 19 and end flap 20. According to conventional practice in the case of hot fill, the whole of the interior of end flaps 20 are sealed to side flaps 19. According to this invention an area which may be in the shape of an inverted triangle or a notch or a sector is left unsealed or lightly sealed at the top center of end flap 20 as indicated by the numeral 25 in the broken away part of FIG. 5. The remaining sealed area is stippled and indicated at 24. In FIG. 6 the unsealedor lightly sealed area is shown at 23a and 23b which combine to provide area 23 when the carton is closed. It has been found that, particularly when the stake point 70 is located at the apex of triangle 25, an effective seal is provided in spite of this unsealed or lightly sealed area. The unsealed area at the top center enables the consumer to start opening the carton and also results in there being less seal to pull apart where the consumer has the least leverage. This arrange¬ ment is considered useful feature because the area of the flaps at the unsealed or lightly sealed area tends to pop out and thus greatly facilitates opening. FIG. 7 illustrates the male jaw of a suitable die 30 including die face portion 31 for pressing together the upper part of side flaps 19, die face portions 32 and 33 for the ends and horizontal stake embossing line 34, vertical stake embossing lines 35 and embossing protrusion 36 for the center stake point. Die face portion 37 which presses flaps 19 and 20 together is cut away at 38 to leave a triangular unsealed or lightly sealed area. This can be used with a matching female die. Alternatives for providing the desired unsealed area would include the use of silicone as a parting agent or " abhesive" to prevent adhesion in area 25. Another possibility if adhesives were used in place of specifically made heat sealing jaws would be to omit adhesive in area 25. These methods are generally more expensive and less reliable because of the risk of misalignment of the parting agent to the desired non- adhering area. Thus, heat seal¬ ing with specially patterned jaws is the preferred method of closure where, as usual, the carton is coated internally with a thermoplastic resin. FIG. 8 illustrates an improved structure which is similar to that illustrated in FIGS. 4 to 6 but showing an unsealed or lightly sealed area at the top of flap 20 immediately above stake point 70 substantially in the shape of a rectangle 25a instead of the triangle of FIG. 5 and showing a further unsealed or lightly sealed area 25b extending between stake point 70 and vertical stake line 21a. Areas 25a and 25b are left unsealed or are lightly sealed by providing a die which applies no pressure or little pressure in these areas. The construction of a suitable die is illustrated in FIG. 9 showing female jaw 41 and FIG. 10 showing male jaw 40. Referring now to FIG. 10, male jaw 40 has a die face 42 having a raised longitudinal rib 43 to provide a horizontal stake line and vertical ribs 44 and 45 to provide vertical stake lines on the side of the container that is to remain sealed and a vertical rib 46 to provide a vertical stake line on the spout end of the carton (i.e. the end that is to be opened) . Male jaw 40 has a set screw 47 to provide a central stake point 70. The generally rectangular relieved area 25a of FIG. 8 is provided by depressed area 48 immediately above set screw 47 and offset in the direction of the side of the carton that is to be opened. A relieved area 49 is also provided extending from set screw 47, which provides center stake point 70, to rib 46 which provides vertical stake line 21a. Male jaw 40 also includes area 50 for sealing side flaps 19 of the carton and areas 51, 52, 53 and 54 for sealing the remainder of end flaps 20. Female die 41 shown in FIG. 9 has an upper area 55 which mates with portion 50 of the male jaw and a slightly undercut area 51 the upper edge of which is located to accomodate rib 43. Die 41 has slots 56 and 57 to accomodate ribs 44 and 45 and slot 58 to accomodate rib 46. It also has a depressed area 59, to relieve pressure, matching area 49 of the male die and generally rectangular pressure relieving area 60 matching area 48 of the male die. FIGS. 11 and 12 show an even further improvement of the male and female jaws respectively. The jaw construction shown therein is similar to that shown in FIGS. 9 and 10 where similar reference numerals are used. However, there are several differences which have been empirically found to yield better results. The differences reside in the region below the longitudinal rib 43 and bet¬ ween rib 45 and rib 46. It should be noted that in all of FIGS. 9-12, the depth of the depressions relative to one another is exaggerated for emphasis. In FIG. 11, the set screw 47 used to define the stake point in the jaws shown in FIG. 10 is replaced with a protrusion 471 which may be of semi-circular shape as shown. The protrusion 471 is in fact recessed from the longitudinal rib 43 but extends out generally as far as the ribs 44, 45 and 46. The male jaw also includes a recessed portion 53 like that of male jaw shown in FIG. 10, but the recessed portion 53 includes an inclined recess portion 494 recessed at an angle of about 30 to 40 with one edge contacting the recessed surface 53 and one edge extending significantly below that surface. Another surface 492 is recessed from the recess surface 53 and,optionally, a further recessed portion 491 is recessed from the portion 492. The female jawsE shown in FIG. 12 are similar to the female jaws shown in FIG. 8 with the exception of modification made in the depressed area 59. Specifically, in the modified jaw, the depressed area 59 is significantly depressed. From this depressed area are provided a number of areas which are less depressed, i.e. , protrude from the depressed area 59. These include the areas 60 and 58 and a protruding area 472 which is adapted as a stake plate for protrusion 471 in the male jaw to provide a heavily staked area. A protrusion such as 36, 47 or 471 is necessary to create a center stake which will block the natural path bacteria might follow to enter the carton. This path would be from the edge of the carton along a channel 28 just above the upper edges 20 a of end flaps 20 as shown in FIGS. 13 and 14 and down into the carton between the folding points of end flaps 20 where a natural gap 29 occurs. Accepted practice dictates that the larger the center stake in the gap region 29 the better. The present inventor has discovered that to ensure the easy open characteristic desired the center stake should be optimally placed below and as close to the upper edge of the end flaps as possible with a shape and area sufficient to adequately close the gap 29 and no more such as shown at 71 in FIG. 14. The present inventor has further discovered that if this is done and area 26 . , being the intersection of the fold or score lines on panel 17, is left substantially unaffected by the center stake, this area will "pop" out during the opening process and greatly facilitate the opening of the carton. It is believed that this arrangement allows sub-panels 17a and 17b to toggle effectively without distortion and thus bring greater force to bear in breaking the seal. Although the location and dimensions of the stake areas and the corresponding design of the jaws have been derived empirically, it has been found that generally the critical areas are those areas necessary to ensure a minimum complete seal of the flaps. Further, it has been found that, by relieving sealing pressure immediately adjacent to critical areas, improved sealing is achieved. Specifically, when the areas immediately adjacent the critical areas are relieved the force applied by the jaws to seal the flaps occurs at the reduced area, i.e. only at the critical areas. Accordingly, When a constant amount of pressure is applied to the jaw, the provision of a recessed area decreases the area of contact upon which high pressure is applied and thus increases the sealing pressure per unit of area over the critical areas; as a result, a stronger seal without an increase in pressure applied to the jaws. Traditionally, gable top cartons were heat sealed evenly across the flaps by flat non-patterned planar jaws . The practice then developped to further strengthen the seal by adding horizontal and vertical stakes and a center stake. It is believed that until the present invention, it was not understood that, so long as a process could be developped which would not create any significant pressure differential across the seal, a practical seal could be achieved by relying principally on the sealing effect of the horizontal, vertical and center stakes. With this realization it became possible to relieve sealing pressure, and thus the bond strength between the flaps forming the seal, over those other areas which would significantly improve the opening characteristics of the carton. The sealing of the gable top carton can be accomplished by employing the techniques described above so as to ensure a strong seal at certain critical areas while maintaining an easy to open carton. To ensure that this seal is adequate to ensure shelf stability, however, the contents must be steril ized or pasteurized in such a way that a stronger seal is not required and additional forces are not applied to the seal. As noted above, this means that the so-called hot fill method of pasteurization is not acceptable because it results in a vacuum which requires a stronger seal. The present inventor has discovered that by combining the sealing technique described above with the following post-packaging pasturization process which does not lead to the creation of a vacuum in the gable top carton, traditional gable top cartons can be used to package shelf stable liquid products and simultaneously retain their easy opening characteristic required in order to achieve consumer acceptance. It is believed that no such practical process has previously been developed for post-packaging pasteurization in easy to open gable top cartons constructed of plastic or paperboard coated with plastic. In accordance with one aspect of this invention, the method of providing liquid food products that are shelf stable in easy to open gable top cartons comprises the steps of: ( a) cold filling a plastic coated gable top carton with an essentially non-carbonated liquid food product free from pathogenic and thermophilic organisms; (b) sealing the carton as described above; (c) heating the food product in the carton to a pasteurization hold temperature in the range of about 160° F and preferably 167 F but below the softening temperature of the plastic; ( d) maintaining the food product at the pasteurization hold temperature for sufficient time to provide an adequate kill of the bacteria remaining within the carton; and (e) cooling. The food products to which this invention is applicable are those which are generally pourable and could be advantageously packaged in gable top cartons, including, for example, liquid dairy products, non- carbonated fruit products such as the citrus products or citrus flavored products, fruit products, vegetables juices and vegetable cocktails. Carbonation must be avoided as otherwise the pressures that would be generated in the carton during the process would be too high. Another requirement of the food product is freedom from pathogenic and thermophilic bacteria. Most juices and drinks have pH' s in the range 2.8 - 4.0 and not above pH 4.6. At a pH above 4.6 there is a potential problem of pathogenic bacteria. Below pH 4.6 the problems are yeast, molds and bacteria. If the pH is above 4.6, which would include such products as milk, then there should be a preliminary ultra high temperature treatment at 240°F to 260°F for 15-20 seconds to kill pathogenic organisms, followed by cooling to ambient temperature. A preliminary ultra high temperature treatment is advisable with some vegetable base products such as tomato, due to their initial high content of thermophil ic molds. The juices and drinks to which this process is applicable are formulated in a tank at ambient temperatures in the range 40 - 75 F and pretreated as discussed above if necessary. They are then pumped to a filling station where the juice or drink is fed into cartons. Although not essential, it may be useful to provide a sparging infusion valve in the line berween the tank and fill ing station. The sparging infusion valve is used to add up to about 0.1 lbs/square inch of nitrogen or carbon dioxide, and preferably about 0.01 lbs/square inch. The purpose of sparging is to create a slight positive pressure to oppose the entrance of any bacteria into the carton after filling- Carbon dioxide is preferred for this purpose. The product sparged with carbon dioxide would have such a small amount of carbon dioxide that it would not be classified as a carbonated product. At the filling station which is of conventional type, a number of individual cartons are filled cold. The temperature of the liquid food product should be less than 80°F and desirably less than 70 F to achieve a neutral or positive pressure after filling. This may be contrasted with hot fill temperatures of the order of 180°F. The maximum temperature that can be used depends on the conditions including the positive pressure from any sparging gas and on the strength of the seal. After filling and closing the cartons there should be a neutral to slightly positive pressure. As previously indicated a vacuum is undesirable. The cold filled cartons are transferred to a processor comprising three zones, a preheat zone, a hold zone, and a cool zone. The processor may be in the form of a continuously moving chain upon which rows of cartons are placed. The cartons are spaced to allow water to run down the sides of the cartons to heat or cool the contents. Heating may also be achieved in other ways such as the use of microwave energy provided no metal is used in the carton structure. 1. Preheat zone The cold filled cartons are preheated preferably by pouring water at a temperature of 180°F - 185 F onto the cartons and allowing it to cascade down the sides. After a period of time that varies with the size of the carton, viscosity, solids content, etc. , the liquid product within it reaches the desired "pasteurization hold" temperature. The preferred temperature for "pasteurization hold" is about 167 F, which will be reached in about 13-19 minutes in the case of 1 liter cartons. Two liter cartons would take 20 to 24 minutes to reach this temperature, while 4 to 7 minutes would be adequate for 250 ml. cartons. If microwave energy were used to heat the product, the time to reach the pasteurization temperature may be different. 2. Hold zone The product is maintained at the required pasteurization temperature for a predetermined time to ensure adequate kill of all microorganisms . The appropriate time at various "pasteurization hold" temperatures is available from standard texts. At the preferred temperature of 167 F a hold time of ten minutes is recommended. The temperature should not be greater than about 174 F, at which the time will be about 4 minutes, as otherwise there may be problems with softening of the plastic where the carton is polyethylene and delamination of foil from paperboard will occur. Slightly higher tempera¬ ture may be used with plastics having a higher softening point such as polypropylene. At lower temperatures the hold time is quite long. For example, at 160 F it would be about 25 minutes. 3. Cool zone After holding for the required amount of time, the cartons go into a cooling zone which, if water chilled, may exit at around 90 F to 105 F. This temperature is desirable as it will quickly evaporate off any excesss moisture adhering to the carton. The temperature of the cooling water may be about 35°F to > 6600°F F.. TThe cartons then leave the processor and are packed in cases. The process is further illustrated by the following examples: Example 1 This example relates to the production of 1000 Imperial gal. of single strength (ready to drink) orange juice. 135 gal. of orange juice concentrate 65 Brix ( % soluble solids) is added to 865 gal. of water and blended for 10 minutes. It is then pumped using positive pumps through a line leading to a filler. The line includes a sparging infusion valve to sparge carbon dioxide to give an end product with about 0.1 lbs/square inch of gas. At the filler the carton is filled at a temperature of about 70 F into one liter gable top cartons which are heat sealed in accordance with the sealing technique described above. The cartons are brought up to a temperature of 167 F in 14 minutes and held at that temperature for 10 minutes. They are then chilled with water at 40 F for 12 minutes to give an exit temperature of 90 F. The orange juice has a desirable shelf life of three months and a recommended maximum of six months. The taste of the orange juice is markedly better than that produced by hot filling. Example 2 This example relates to a Caesar' s clam juice cocktail. A thousand imp. gal. batch was made of water and 100 imp. gal of tomato paste (32-34 brix) 650 lbs of salt; 60 lbs of monosodium glutamate; 700 lbs of glucose solids; 30 lbs of spices and 10 gal. of clam broth. It is pumped to a pasteurizer where the product is brought to a temperature of 250 F in about 10-20 seconds, and held at this temperature to 48 to 52 seconds, cooled at 70 F and then filled and processed as described in Example 1. Example 3 This example relates to the packaging of milk in a shelf stable easy to open gable top carton. The milk is first pasteurized at a conventional UHT temperature such as 250 F for approximately 8 seconds then immediately cooled to ambient temperature. The milk is then cold filled into gable top cartons in the norm al manner under stringent sanitary conditions and then sealed and processed as des¬ cribed in Example 1.

Claims: CLAIMS: 1. A method of shelf stable packaging a perish¬ able liquid food product in a gable top carton which is internally coated with thermoplastic and which includes sealing flaps which comprise side flaps and inwardly folded end flaps, the lower edge of each of said flaps being defined by a horizontal fold line where the flaps splay to form the top of the carton, each of the flaps having an upper edge, the upper edge of the side flaps extending beyond the upper edges of the end flaps, one set of which end flaps being outwardly foldable to form a spout, the method comprising the steps of: a) ensuring that the liquid food product is free from pathogenic and thermophilic organisms; b) filling the carton with the liquid food product maintained at substantially room temperature; c) hermetically sealing the carton by applying heat and a predetermined amount of pressure to predetermined portions of the sealing flaps and applying less pressure to other portions of the sealing flaps so as to produce an easily opened seal; d) heating the food product in the sealed carton to a temperature sufficient for pasteurization but below the softening temperature of the thermo¬ plastic coating; e) maintaining the food product at the pasteurization temperature for sufficient time to kill essentially all microorganisms remaining within the carton; and, f) cooling the gable top carton and its contents . 2. A method as in claim 1 in which the predeter¬ mined portions of the sealing flaps include: a) a horizontal stake line extending the full length of the side flaps at a level just above the upper edge of the end flaps; b) at least one vertical stake line located inwardly of each end of the flaps extending downward from the horizontal stake line to the horizontal fold line; c) a center stake of a size and shape sufficient to cover portions of both of the end flaps and being located above the horizontal fold line. 3. A method as in claim 2 in which pressure is further relieved over a first area between the upper edge of the end flaps and the horizontal fold line which area extends from the center stake region out¬ wardly toward the spout end of the carton. 4. A method as in claim 3 in which the first area is in the shape of a triangle tapering towards the spout end of the carton. 5. A method as in claim 3 in which the center stake is located above a point mid-way between the upper edge of the end flaps and the horizontal fold line. 6. A method as in claim 3 in which pressure is further relieved over a second area extending below the upper edge of the end flaps between the center stake and the vertical stake on the spout end of the carton. 7. A method as in claim 2 in which pressure is further relieved over a second area extending below the upper edge of the end flaps between the center stake and the vertical stake on the spout end of the carton. 8. A method as in claim 7 in which the pressure over the second area is relieved progressively from the horizontal stake line down. 9. A method as in claim 2 in which the center stake is located above a point mid-way between the upper edge of the end flaps and the horizontal fold line. 10. A method as in claim 1 in which the predeter¬ mined portions of the sealing flaps include: a) a horizontal stake line extending the full length of the side flaps at a level just above the upper edge of the end flaps; b) at least one vertical stake line located inwardly of each end of the flaps extending downward from the horizontal stake line to the horizontal fold line; c) a center stake of a size and shape sufficient to cover portions of both of the end flaps and being located above a point mid-way between the upper edge of the end flaps and the horizontal fold line; and where, d) pressure is further relieved over a first area between the upper edge of the end flaps and the horizontal fold line which area extends from the center stake region outwardly approximately one third the distance toward the spout end of the carton; and, e) pressure is progressively further relieved from the horizontal stake line down over a second area extending below the upper edge of the end flaps and centered approximately two thirds of the way between the center stake and the vertical stake on the spout side of the carton. 11. A method as in claim 1 in which the pasteuri ation hold temperature is in the range of 160 F to 174 F. 12. A method as in claim 1 in which the thermo¬ plastic is polyethylene and the pasteurization hold temperature is in the range of 160 F to 174 F. 13. A method as in claim 1 in which the pasteurization hold temperature is about 167 F. 14. A method as in claim 1 in which the food product is maintained at a pasteurization hold temperature of about 167 F for about 10 minutes. 15. A method as in claim 1 in which after pasteurization the fbod product is cooled by chilled water to a temperature of about 90 F to 105 F. 16. A sealed gable top carton and a perishable liquid food product contained therein, the gable top carton having a gable closure which includes opposed side panels with side flaps extending therefrom and opposed end panels with end flaps extending therefrom to a lower height than the height of the flaps of the side panels, said side panels and end panels having fold lines to facilitate closing and opening, the opposed side flaps being adhered to each other and the end flaps being adhered to the lower portions of the side flaps, the carton being sealed by applying varied pressure across the flaps so that different regions of the flaps are sealed with different amounts of pressure to provide a strongly sealed area and a first lightly sealed area at the center of and at the upper portion of an end flap to facilitate opening of the carton by a consumer; the perishable liquid food product being filled into the carton at about room temperature before the carton is sealed, heated to a pasteurization hold temperature after sealing and maitained at the pasteurization hold temperature for a time sufficient to pasteurize the product and sterilize the interior of the carton. 17. A gable top carton as in claim 16 in which at least the interior of the carton is coated with a thermoplastic . 18. A gable top carton as in claim 17, in which the flaps are adhered by heat sealing. 19. A gable top carton as in claim 16, in which the lightly sealed area is in the shape of a triangle. 20. A gable top carton as in claim 16, in which there is a stake point immediately below the lightly sealed area. 21. A gable top carton as in claim 16, in which a second lightly sealed area is provided in the end flap having the first lightly sealed area, said second lightly sealed area extending along the lower portion of the end flap from substantially the center to a point spaced from the outer edge. 22. . A shelf stable system for storing perishable liquid product comprising: a thermoplastic coated gable top carton, the carton having a gable top closure which includes closure sealing flaps which can be sealed to one another by applying heat and pressure to the flaps; a perishable liquid food product; wherein the product is cold filled into the carton before the carton is sealed and the carton is then sealed by applying different amount of pressure to different regions of the flaps so as to provide a hermetic easy to open seal; wherein the sealed carton and perishable product are then heated to a pasteuri ation hold temperature, maintained at the pasteuriz tion hold temperature for a time sufficient to kill essentially all microorganisms remaining in the carton and then cooled such that the product is shelf stable within the sealed carton. 23. A sealed gable top carton and a perishable product contained therein; the gable top carton comprising a bottom panel, opposed side panels and opposed end panels and a gable top, the gable top being formed by folding and sealing the side and end panels to one another, the gable top carton having a thermoplastic surface layer which softens at a predetermined temperature, the gable top carton including a top sealing portion for sealing the interior of the carton, the top portion having a plurality of regions, each region being sealed with a different amount of pressure so as to provide a hermetic seal which is easy to open; the product being cold filled into the carton before sealing of the carton and the product being heated and maintained at a pasteuriz tion hold temperature after the carton is sealed, the pasteurization temperature being sufficient to kill essentially all microorganisms remaining in the carton but below the predetermined temperature at which the carton' s surface layer softens; the carton being sufficiently sealed to ensure that the product is shelf stable. 24. A process for packaging a perishable liquid product free from pathogenic and thermophilic organisms in a shelf stable gable top carton which has a temperature surface layer which softens at a predetermined temperature and includes opposed side panels with side flaps extending therefrom to a lower height than the flaps of the end panels, the process comprising the steps of: a) cold filling the gable top carton with the product; b) sealing the carton by applying heat and pressure to opposed side flaps to soften the thermoplastic layer so that the opposed flaps adhere to each other and the end flaps adhere to the lower portions of the side flaps and of the upper portion of an end flap to form a lightly sealed area which facilitates opening of the carton by a consumer; c) heating the product in the sealed carton to a pasteurization hold temperature which is above the pasteurization temperature of the product but below the softening temperature of the gable top carton surface layer material; d) maintaining the food product at the pasteurization hold temperature for sufficient time to provide an adequate kill of micro¬ organisms in the carton; and e) cooling the product within the carton. 25. A shelf stable package comprising a gable top carton containing a perishable product, the carton having a surface layer which softens at a predeter¬ mined temperature and including opposed side panels with side flaps extending therefrom and opposed end panels with end flaps extending therefrom to a lower height than the flaps of the side panels, the package being made by a process comprising the steps of: a) cold filling the gable top carton with the product; b) hermetically sealing the carton by applying heat and a first amount of pressure to predeter¬ mined critical areas of the opposed side flaps to soften the surface layer such that these critical areas adhere to each other and the end flaps adhere to the lower portions of the side flaps and applying a second amount of pressure, which is less than the first amount of pressure, to other, non-critical, areas of the flaps so as to leave areas which are lightly sealed at the center of the upper portion of the end flaps to facilitate opening of the carton by a consumer; c) heating the product in the sealed carton to a pasteurization hold temperature equal to or greater than the pasteuri ation temperature of the product but below the softening temperature of the gable top carton material; d) maintaining the food product at the pasteurization hold temperature for sufficient time to provide an adequate kill of micro¬ organisms in the food product; and e) cooling the product within the carton. 26. A method of shelf stable packaging a perish¬ able liquid food product in an easy opening gable top carton which is internally coated with thermoplastic and which includes sealing flaps which comprise side flaps and inwardly folded end flaps, the lower edge of each of said flaps being defined by a horizontal fold line where the flaps splay to form the top of the carton, each of the flaps having an upper edge, the upper edge of the side flaps extending beyond the upper edges of the end flaps, one set of which end flaps being outwardly foldable to form a spout, the method comprising the steps of: a) ensuring that the liquid food product is free from pathogenic and thermophilic organisms; b) filling the carton with the liquid food product maintained at substantial y room temperature; c) closing the carton so that the sealing flaps are adjacent one another; d) joining predetermined portions of the adjacent sealing flaps so as to hermetically seal the carton and to produce a seal which is easily opened; e) heating the food product in the sealed carton to a temperature sufficient ~ for pasteuri¬ zation but below the softening temperature of the thermoplastic coating; f) maintaining the food product at the p steurization temperature for sufficient time to kill essentially all microorganisms remaining within the carton; and, g) cooling the gable top carton and its contents. 27. A method as in claim 26 wherein the liquid food product contains no artificial preservatives. 28. A method as in claim 26 wherein the temperature of the liquid food product at the time of filling into the carton is in the range of 60 -80 F. 29. A method as in claim 26 wherein the liquid food product is filled into the carton in an environ¬ ment which is open to the atmosphere. 30. A die for sealing a heat sealable carton having a gable shaped closure, said gable shaped closure including side flaps extending from opposed side panels and end flaps extending from opposed end panels to a lower height than the flaps of the side panels, the end flaps having adjacent portions when inwardly folded to provide said closure, and at least one end panel having score lines to facilitate opening and closing one end of the carton, the die including a pair of jaws, each of the jaws having an upper surface for pressing together the side flaps that are above the end flaps, said jaws having lower surfaces for pressing together the side flaps and folded end flaps, a recessed area in at least one of said lower surfaces to provide an area that is not firmly adhered at the center of the upper portion of said end flaps to facilitate opening of the carton and one of said dies having a protrusion immediately below said recessed area to provide a center stake point which presses together, expands into abutment and seals said adjacent edges of the inwardly folded end flaps. 31. A die as in claim 30, in which a linear horizontal rib is provided in one of said jaws at the junction between the upper surfaces and the lower surfaces, acting in cooperation with the other of said jaws to provide a horizontal stake line just above the upper edges of the end flaps. 32. A die as in claim 31, comprising on one of said jaws vertical ribs extending downwardly from said horizontal rib to provide vertical stake lines adjacent to each end of the side flaps. 33. A die as in claim 32, in which there is an additional recessed area below said recess and extending between one of said vertical ribs and the center of the die. 34. A die as in claim 30 wherein said protrusion has a semi-circular shape in the plane of the jaw from which it protrudes. 35. A die as in claim 30 wherein the protrusion is located to provide a center stake point immediately below the upper edge of the end flaps. 36. A die as in claim 32 comprising in one of said jaws a first recessed area in the lower surface extending from the area of the protrusion outwardly toward the end of the jaw corresponding to the spout end of the carton to a point proximate to one of the vertical ribs . 37. A die as in claim 36 comprising a second recessed area centered approximately two thirds of the way between the protrusion and the vertical rib on the spout end of the carton said second recessed area being progressively recessed from the plane of the first recessed area commencing at the horizontal rib. 38. A gable top carton with an easy open toggle top, the carton comprising a carton body and a gable top closure which can be opened to form a pouring spout, the closure including opposed side panels with side flaps extending therefrom and opposed end panels with end flaps extending therefrom to a lower height than the height of the flaps of the side panels, the side panels and end panels having fold lines to facilitate closing and opening, the score lines on at least one end panel intersecting at a point corres¬ ponding to the tip of the pouring spout from which the end panels extend, the closure being sealed by forming a seal across the flaps such that the carton is hermetically sealed and so that the area of the flaps immediately adjacent the intersection of the score lines is unsealed or lightly sealed so that during opening, this area will pop out to facilitate opening of the carton. 39. The gable top carton of claim 38 wherein a perishable liquid food product is filled into the carton at about room temperature before the carton is sealed, and the product is heated to a pasteurization hold temperature after sealing and maintained at the pasteurization hold temperature for a time sufficient to pasteurize the product and sterilize the interior of the carton. 40. The gable top carton of claim 38 wherein the interior of the carton is coated with a thermoplastic. 41. The gable top carton of claim 40 wherein the carton is sealed by applying heat and a first amount of pressure to predetermined areas of the opposed side flaps and end flaps to cause these areas of the opposed side flaps to adhere to each other and these areas of the end flaps to adhere to the lower portions of the side flaps and applying a second amount of pressure, which is less than the first amount of pressure, to other areas of the flaps so as to leave areas which are lightly sealed at the center of the upper portion of the end flaps to facilitate opening of the carton by a consumer and wherein the area of the flaps immediately adjacent the intersection of the score lines is left substantially unsealed. 42. A method of forming an easy open pop out seal in a gable top carton closure which includes opposed side panels with side flaps extending therefrom and opposed end panels with end flaps extending therefrom to a lower height than the height of the flaps of the side panels, the side flaps and end flaps each having an inner surface and an outer surface and each end flap having a vertically extending horizontal center line region, the method comprising the steps of: a) folding the end flaps along the center line region such that a first half of the outer surface of each end flap is folded on to the other half thereof and the inner surface of each end flap is folded against the inner surfaces of adjacent side flaps and so that the center line region of the opposed end flaps are adjacent one another and separated by as small a vertical gap as possible, said small vertical gap being bounded by the opposed end flap center line regions and inner surfaces of opposed side flaps; b) attaching at least a portion of the inner surface of each end flap to the inner surface of the side flap it is folded against; and c) forming a seal across the upper portion of said gap so as to seal said gap without sealing the lower portion of said gap so as to provide a pop out closure. 43. A sealed gable top container with a pop out closure, the container comprising a container body and a gable top closure, the gable top closure including two opposed side panels with side flaps extending therefrom and two opposed end panels with end flaps extending therefrom, the side flaps and the end flaps each having an inner surface and an outer surface, the end flaps being folded along a fold line such that a first portion of the outer surface of each end flap is in planar contact with another portion of the outer surface of the flap and the inner surfaces of each of said end flaps being sealed to the inner surfaces of the side flaps and the fold lines of each of the opposed end flaps being adjacent and separated from one another by a vertically extending gap bounded by the portions of the inner surfaces of the end flaps and side flaps and the upper portion of the gap being sealed from the upper edge of the end flaps to a point above the vertical mid point of the end flaps and the lower portion of the gap being substantially unsealed. 44. A method as in claim 27, wherein the liquid food product remains shelf stable without refrigeration for at least three months.

Inventors: POOLE DONALD A, POOLE, DONALD, A.
Applicants: FBI BRANDS LTD, FBI BRANDS LTD.
Application year: 1990
Main classification: B65D5
IPC codes: B29C65, B31B3, B65B51, B65B55, B65D5