CA1336147C - System for packaging perishable liquids in gable top cartons - Google Patents

Abstract

A method for the shelf stable packaging of perishable liquid food products in hermetically sealed easy-to-open gable top cartons comprising the steps of cold filling liquid food products free from pathogenic and thermophilic organisms into gable top cartons, sealing the cartons over certain critical areas of the seal flaps while reducing or relieving sealing pressure over certain other specified areas, heating the sealed carton up to and holding the contents at a pasteurization hold temperature for a predetermined time and then cooling the contents of the carton.

Description

~ 1336147 SYSTEM FOR PACKAGING PERISHABLE
LIQUIDS IN GA~LE TOP CARTONS

FIELD OF THE INVENTlON

Thts invention relates to the shelf stable packaging of perishable ~uices and other perishable liquid products tn hermétically se`aled gable top cartons acceptable to the consumer. A packaged product ts satd to be shelf stable when 5 it retains its desirable qualtties for an extended pertod of time without refrigeration .

BACKGROUND OF THE lNVENTlON

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 ]0 must be considered numerous factors. These include cost of the container and packaging process, structural tntegrity and weight of the package, handling convenience for the packer and convenience for the consumer i.e., can the container be tightly packed? Is tt fragile? The packer must also consider the 15 distribution network and infrastructure available in the market - sought to be served: is refrigeration available, if not, the packaged product must be rendered shelf stable?

A packa~e which is too costly in relation to the value of the product itself or which is inconvenient in some 20 respect for the consumer will meet with market resistance and likely fail to win a sufficient degree of acceptance to be commerctDlly viable.

Tradittonally juices have been packed in cans and `~ glass bottles. The technology applicable to these packages is 25 well known. Juices packed tn these containers may be kept unrefrigerated for extended periods provided that these products and their containers ha ve been sterilized ond hermetically sealed tn order to prevent entry of bacteria.

These containers have achieved wide acceptance throuQh use. They may be easily sterilized and sealed effectively. They tolerate both tnternal vacuum and posttive pressure. Closures such as twist off lids for bottles are - 2 - 1~ ~6 1 ~ 7 a~:~ept~,ble 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 end thus may be sterilized at usual temperatures without deteriorating their 5 struct ura I qu alities .

Among the disadvantages of glass bottles and cans are cost and the weight which they add to the product. Also, because of their shape, cans and bottles cannot be tightly packed, In the ca se of bottles their relative fragility is also a 10 dis a d v a nta ge .

More recently greater use of so-ca lled 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 packa~ing refrigerated non-shelf stable liquid products such as milk and other dairy products and fruit juice products. The 20 brick pack, so called because of its shape, has been extensively used in association with an aseptic packing process for fruit juices packaged for shelf stability and which therefore do not re qu i re re fri g er a tion .

The gable top carton is relatively inexpensive and 25 light wei~ht. Moreover, because of its planar sides it can be tightly packed for shipping and storage. The gable top carton ~1 enjoys wide acceptance in the publtc 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 30 to- be lightly shoken without 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 larsely overcome in the dairy ond fruit ~uice industry by simply weakening the seal 35 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 "abhesive" be applied to selected areas near the spout in order to reduce the ............. , , -plastic-to-plastic bond formed during the sealing process.
The method adds to the cost of the carton and quality control as to the precise placement of the adhesive 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 ~ 4.~ ~6~7 ~ ppocioe end wall portions ~!re folded like bellows between the outer marginal portions of the two remainin~ end wall portions and at least one of the two inwardly folded marginal portions-is moveable outward together with the pertaining end wall portions 5 from its position between the two outer marginal portions to a new position outside these where the marginal portion after bein~8 moved outward, as well a5 its pertaining end wall portion, form a ;pouring spout and an emptying passage.

Traditionally, dairy products and fruit juices packed ]0 in gable top cartons have been kept refrieerated throughout the distribution process in order to avoid almost immediate spoilaQe.
This spoilage wol~ld 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 15 quickly. It Is only refrigeration which retards spoilage for up to a couple of weeks. Products packed in this way are not said to be shelf stable.

Shelf stability i s extremely desirable from many standpoints . A shelf stable product i s much less likely to spoil 20 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.
~imilarly the retailer need not allocate expensive refrigerated 25 space to store its supply of product. The consumer also has the advantage of a product which does not require refrigeration unt il opened .

Shelf stability may only be achieved in two ways.
First, use may be made of chemical preservatives.
30 Alternatively, precsutions 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 8 juice or similar liquid food product without using chemical preservatives ~35 the product must be sterilized ~said to be pasteurized).
Followin~, pasteurtzation no bacteria must be permitted to come into contact with the product. ~o ensure that this is the case, all bacteria which may come into contact with the product prior to or at the time of fillinQ and sealing oî the carton, all .. - -- ~

C A 1 3 3 6 1 4 7 ,~
baCt.eL'ia Wit~ fle ca~lo~ ~nd all ~,dcteria in the environment which becomes trapped in the carton after sealing must be 'killed. Failure to do so will inevttably lead to spoilage.
, With' glass containers and cans a process known as 5 post packaging sterilization ha s been employed to achieve shelf stability. The ~iquid is poured into a non-sterile container, the container is capped and sealed; the container and its contents are héated to an`d maintained at a sterilization temperature until all the bacteria within the container are killed; the container is 10 then cooled; the product is then shelf stable.

This process ha s 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 exarrple, U.S. patents 4,088,444 to Byrne and 2,995,418 to Muller 15 each disclose a sterilization process wherein a container formed from flexible material such as plastic i5 filled 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 contsiners reaches the sterilization temperature, maintaining 20 the temperature at the sterilization temperature until sterilization is effected, and thereafter cooling the liquid in the containers by subjecting the containers to cold water. I~uller in particular ,pecifically ccntemplates sterilizing fruit juices which are in sealed plastic containers.

I,'.S. patent 4,376,126 to Evers discloses a method of making a yogurt beverage which includes the steps of pD steurization or sterilization after the beverage ha s been packed in a container. Evers, however, does not appear to specifically disclose the use of any particular container nor 30 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 35 plastic containers, whereby the food is sub~ected to heating and then cooling after being sealed in the containers. 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.

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13b36147 U.S. patent 237,449 to Schaum erg et al. discloses a rnethod of preserving fruit juices in glass boItles that includes bottling and sealing the juices and thereafter heatin3 ohe ~uices to 170F for 35 minutes . However, Scha umberg et al . does not 5 disclose subjecting the heated bottles to a coolin~ process and does not contemplate the use of plastic or plsstic 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 lO 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 ]S used for packagin~ shelf stable products. These are the aseptic process, promoted since the early 1960' s by Tetra Pak of Sweden principally in association with the so-called brick pack, and the hot fill process more recently a dapted 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 sterlle environment until filling and sealing. The seal must 2S 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 advantaQeous from a consumer convenience point of view. The a septic method is complicated to carry out and 30 requires specialized and expensive equipment.

No`twithstanding the comp]exity 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 35 that time. Prior to the introduction of the aseptic process and the brick pack there were no shelf stable products packaged in paper-based contalners. The useptlcally packed brick pack created a whole new application for paper-based containers.
The success of the aseptically packed brick pack has been ,~
~ri.

~7- 1~36147 nothing short of phenomenal. It is estimated that, on a worldwide basis, asepttcally packed brick packs account for over $20 bil]ion dollars worth of liquid food products.

Because of the complexity and cost of the aseptic 5 process, efforts were made to achieve shelf stability in paper-based containers, most desirab]y with the popular gable top carton, with simpler less expensive technology. In the early 1980 s a so called hot fill process was proposed.

A less costly alternative to the aseptic method, the 10 hot fill method did not meet with~much success. In accordance with the hot fill method the pa steurized product is heated to temperatures in the range of lôS degrees ~ 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 ]5 container after sealing.

In the llnited 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 20 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 spoi~age unless the product is refrigerated. In order to deal with this problem the seal must be strong enough to 25 withstand the significant pressure differential created by the rocess. The seal must also be strong enough to retain its integrity in al~ 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 prob~ems created by th 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 ., . , ... ~.. . ..
,, .

- - 8 ~336~7 proponent of the hot fill technology, deveioped an &l~ernative form of opening the carton, subject of l~S patent No. 4,527,732 issued in 1985, which covers a scored "smile" to be pushe,d throuQh by the consumer.

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 handling qualities all at reasonable cost have heretofore not proven successful; and this despite the fact that finding sn uncomplicated and inexpensive 10 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 packagtng of perishable liquids which allows use of a 15 gable top carton which can be hermetically sealed to ensure shelf stability while retaining an easily opened spout necessary for consumer acceptance.

SU~ iARY OF THE INVENTION

The present invention overcomes the difficulties referred to sbove in adapting the gable top carton for the 20 packaging of shelf stable liquid producis 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 interrelationship between the strength of seal necessary to maintain hermeticity and the 25 process used to sterilize the gable top carton.

Having recognized this, the present inventor has determined that the lack of commercially viable system for shelf stable packaging in gable top cartons is primarily due to a failure to find an acceptable compromise between hermetically 30 sealing and ease of opening of the sealed spout of the S~able 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 35 stability wlth an easy to open gable top carton can be achieved through the selection of an appropriate post-pa sturization process combined with an appropriate seal design. The inventor .~.. . . ... ... .

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CA 1336147 - 9 -i has also di5covered that an adequate seal which is still easy to open can be achieved by applying increased pressure at certain empirically lo~cated critical points along the seal. If these critical points are adequately sealed, the remainder of the seal 5 can be sesled in an easy open fashion. Consequently, the spout is still easy to open.

- ~ 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 10 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.

In accordance with the present invention, the liquid food product to be packed is first pasteurized, if required, in 15 accordance with procedures appropriate to particular product.
The product is then cooled to room temperature and introduced into gable top cartons which are then satisfactorily hermetically sealed at the ernpirlcally determined critical points slong the sealing portion of the gable top carton in accordance with the 20 method described below in such a wa y as to permit their ea se of opening for the consumer. The filling process is open to the environment.

The sealed cartons are then heated to and held for an appropriate time at a post-pasteurization temperature 25 appropriate to kill the environmental bscteria, 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-pa steurization temperature in the range of Dbout 160F is 3 appropriate with a preferred temperature of about 167F 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 35 across the seal) and thus there is no dan8er that environmental bacteris will be drawn into the carton in the event the integrity of the seal is s~bsequently lost. While the seal is hermetic, it need not be as stron~ 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.

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.: .,-- 9a -Thus in accordance with one aspect of the invention there is provided a method of shelf stable packaging a perishable 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 thermoplastic 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.

-9b-In accordance with another aspect of the invention there is provided 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, both said side flaps and said end flaps each having upper portions and lower portions, 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 maintained at the pasteurization hold temperature for a time sufficient to pasteurize the product and sterilize the interior of the carton.

133~147 . - 9c -In accordance with still another aspect of the invention there is provided a shelf stable system for storing perishable liquid product comprising: a thermop'astic 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; and, 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; and, wherein the sealed carton and perishable product are then heated to a pasteurization hold temperature, maintained at a pasteurization 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.
In a still another aspect of the invention there is provided a sealed 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 table 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;

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13361~7 ! - 9d -the product being cold filled into the carton before sealing of the carton and the product being heated and main'~ained at a pasteurization hold temperature after the carton is sealed, the pasteurization temperature being sufficient to kill essentially all microorganisms remaining in the c~rton 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.
In yet another aspect of the invention there is provided 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 and to oppose 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 applying less pressure to an area at the center 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 microorganisms in the carton; and e) cooling the product within the carton.

- 9e -In a still further aspect of the inventi~n there is provided a shelf stable package comprising a gable top carton containing a food product, the carton having a surface layer which softens at a predetermined 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, said side flaps having lower portions and said end flaps having upper portions, 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 predetermined 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 portions 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 pasteurization 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 microorganisms in the food product; and e) cooling the product within the carton.

~ ~3361~7 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 retaine,d which is not possible with the hot fill method because the seal 5 must be very strong in order to overcome the pressure differential across the seal created by thst 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 immedistèly draw harmful microorganisms into the container 10 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 t,he seal or leak elsewhere will not result in microorganisms being drawn into the carton and th u s spoila ge will be avoi ded .

~5 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 sseptic 20 process ln operations of a certain size. The present invention is also more secure than the aseptic process. Packing in the asertic 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 25 have been separately sterilized and before the package is sealed, then spoila~e will occur. The present invention permits the filling to be done in an open environment because the bacteris is killed after the package is sealed ~nd no further opportunity for bacteria to enter the carton occurs.

30 Another advant~ge of the present invention over the aseptic process is that the present invention does not require a sterilizing agent such as hydrogen peroxide. With the aseptic `~ process it is slways possible that traces of hydrogen peroxide re~ain on the inside surfsce of the container and contaminate 35 the product. The use of hydrogen peroxlde also presents a problem for workers packing the product. If for any reason the ventilation system required to evacuate hydrogen peroxide vapours Eihould not operate properly, the atmosphcre in the packing area may very quickly become contaminated and pose a health hazard to the workers. The present invention presents no such danger.

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FIG. l is a perspective view Or a conventional gabletop carton having an arrangement in a closed state FIG. 2 is a perspective view of the package of FIG. I in an open state;

FIG. 3 shows part of a blank for making a gable top carton;

FIG. 4 is a perspect~ve 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 Or a die for producing the embodiment of FIG. 8;
and FIG. 10 is a perspective side elevation view of the male portion of a dic for producing the embodiment of FIG. 8.

`~ FIG. ll 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 25 jaw for sealing a gable top carton;

FIG. 13 is a cut-away view Or a gable top carton;

FIG. 14 is a side view Or the top of a gable top carton .

~, DETAILED DESCRIPTION OF THE INVENTION 133~147 FI~S. 1-3 show a conventional gable top carton cons-truction .

The package shown in the drawings has four sidewalls I and a bottom (not shown). Furthermore, the 5 package`has fou~ end wall portions 2 which are united on one hand with the sidewalls I 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 10 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 15 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 additior;al barrier layers. The preferred structural material of the present invention is in five layers, namely, an inner coating of polyethylene and alumLnum (or other satisfactory barrier material) barrier, another polymeric layer to bond the foil, a ; layer of pa'per 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 terephalate, 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 Or 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.

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r ~ 3 3 ~ ~ 4 7 ~ 3 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 loeated in said zone i5 pulled out to the position shown in FIG. 2, where the marginal and the end wall 5 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 wl~ich i5 to form the inside surface of the marginal and end wall portion of the package, which can be opened.
10 The blank is provided with fold or score lines along which the blank is to be folded as to form the finishéd package.

Referring now to FIGS. ~ and 6, the carton illustrated is mainly of conventional construction. It includes opposed pairs of side walls 10 and 11, connected by a fifth 15 panel 12. There is a bo~tom 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 Or top or side flaps 19 are extensions of side 20 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 25 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 l9 and 20 are sealed over their entire surfaces. It is also known to provide further ` additional optional sealing such a s a pair of vertical stake 30 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 35 center stake point 7O which presses toeether, expands into abutment and seals the adjacent edges of the inwardly folded end flaps 20. The foregoing is conventional structure.

The present 1nventor has discovered that, in combination with an appropriate post-pasturization process, the said optional sealing areas are the truly eritical ones. If .,.

r:
~33~47 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-pasteurization 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 r- ~;ning sealed area is stippled and indicated at 24. In FIG. 6 the unsealed or 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.

- 14a - 1336147 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.
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 l9k, 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 vertical 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.

1~
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 m'ade heat r ~ ~
sealing jaws would be to omit adhesive in area 25. These ~ 6 1 ~1 methods are generally more expensive and less reliable because of the risk of misalignment of the parting agent to the desired non-adhering, srea. Thus, heat sealing with specially patterned jaws is the pref,erred 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 FI~GS. 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 ]5 rectanQle 25a instead of the tri~ngle of FIG. 5 and showing a further unsealed or lightly sealed area 25b extending between stake point 70 and vertical stake line 21a. Aress 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 FlG. 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 i s 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 directio,n of the side of the carton that is to be opened. A
relieved area 49 is also provided extendin~3 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 or the male jaw and a slightly undercut area Sl the upper edge Or 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. lt also has a ~, ., . _ , r -- ~6 -- i3 3 6 ~ ~7 depressed area 59, to relieve pressure, matching area 49 of the male die ~nd generally rectangular pressure relieving area 60 matching area 48 of the msle die.

FlGS. 11 and 12 show an even further improvement of 5 the male and fem~le ~aws respectively. The jaw construction shown thereln is similar to that shown in FIGS. 9 and 10 where similar reference~ numerals are used. However, there are several differences which have been cmpirically found to yield better results. The differences reside in the region below the longitudin~l rib 43 and between rib 45 ~nd rib 46. It should be noted that in all of FlGS. 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 ~aws shown in FlG. 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 ~aw also includes a recessed portion 53 like that of male ~aw shown in FlG. 10, but the recessed portion 53 includes an inclined recess portion 494 recessed at an an~le of about 30to 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 691 is recessed from th~ portion 492.

The female jaws shown in FIG. 12 are similar to the female ~aws shown in ~IG. 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 ts adapted as a stake plate for protrusion 471 in the male jaw to provide a heavtly 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 20a 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.

. . .,, w , ' 1336~47 l 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 t 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 pres~ure per unit of area o~er the critical areas; as a result, a stronger seal without an increase in pressure applied to the jaws.

.. .

' -- 17a -Traditionally, gable top cartons were heat sealed evenly across the flaps by flat non-patterned planar jaws.
The practice then developed 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 developed 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.

~ - 18- ~3361~7 The ` sesling of the gable top carton can be accomplished by employing the techniques described above so as to ensure ~ strong seal at certain critical areas while maintaining an essy to open carton. To ensure that this seal 5 is adequate to ensure shelf stability, however, the contents must be sterilized or pasteurlzed in such a way that a stronger seal is not requlred snd sdditional forces are not spplied to the seal. As noted above, this means that the so-called hot fill method of pasteurization is not acceptable because it results in 10 a vacuum which reo,uires a stronger seal.

The present inventor has discovered that by combining the sealing technique described above with the following post-pack~ging pasturizatlon process, traditional gable top cartons c~n be used to package shelf stable llquid products 15 and simultsneously retain their easy openlng characteristic required in order to achieve consumer accepta nce .

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 plsstlc or 20 paperboard coated with plastic.

ln 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 25 with an essentially non-carbonated liquid food product free from pathogenic Pnd thermophillc orgsnisms;
(b) sealing the carton as described sbove;
(c) heating the food product in the carton to a pa steurization hold temperature in the range of ~bout 160 F
30 and preferably 167 F but below the softening temperature of the plastic;
(d) malnt3inlng the food product st the pssteuri2stion hold temperature for sufficient time to provide an adequate kill of the bscteria remaining within the carton;
35 and (e ) cooling .

The food products to which this invention is applicable ~re those which are generally pourable and could be advantageously packaged in gable top cartons, includinQ, for .. ... ., . ;, b -~ - 19 1336147 example, liquid dairy products, non-carbonated fruit products such as the citrus products or citrus flavored products, fruit products, vegetsbles ~uices 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.

S 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 pr~blems are yeast, molds and 10 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 ot 240F to 260F for 15-20 seconds to kill patho~enic organisms, followed by cooling to ambient 15 temperature. A preliminary ultra high temperature treatment is advisable with some vegetable base products such as tomato, due to their initial high content of thermophilic molds.

The ~uices and drinks to which this process is a?plicable are formulated in a tank at ambient temperatures in 20 the rsnge 40 - 75F and pretreated as discussed above if necessary. They are then pu nped to a fillin'g 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 filling 25 station. The sparging infusion valve is used to add up to about 0.1 Ips/square inch of nitrogen or carbon dioxide, and preferably about 0.01 Ibs/square inch. The purpose of sparging is to create a slight positive pressure to oppose the entrance of sny bacteris into the carton after filling. Carbon dioxide is 30 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 35 of the liquid food product should be less than 80F and desirably less than 70F to achieve a neutral or positive pressure after filling. This may be contrasted with hot fill temperatures of the order of 180F. The maximum temperature . .

- that can oe used depends on the conditions including the positive pressure from any spar3ing gas and on the strength of the ~eal. After filling and closing the cartons there should b,e a neutral to slightly posltive pressure. As previously indicated 5 a vacuum is undcsirable.

The cold filled cartons are transferred to a processor comprising three zones, a preheat zone, a hold zone, snd a cool ( A ~ ~ 3 ~ 1 4zone .

The processor may be in the form of a continuously lO 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 provlded no metal is used in the cMrton structure.

1. Preheat zone 15 - The cold filled cartons are preheated preferobly by pouring water at a temperature of 180F - 185F onto the cartons and allowlng it to coscade 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 20 "pa steurization hold" temperature . The ?referred temperature for "pasteurization hold" is about 167F, 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 resch this temperature, while 4 to 7 minutes would be adequate for 250 ml. cartons. If 2~ 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 e predetermined time to ensure '-adequate kill of all microorganisms. The appropriate time at 30 various "pasteurization hold" temperatures is available from sta ndard texts . At the preferred temperature of 167F a hold time of ten minutes is recommended. The temperature should not be greater than about 174F, at whlch the time will be about 4 minutes, as otherwise there may be problems with softening of 35 the plastic where the carton is polyethylene and delamination of fo~l from paperboard will occur. Slightly higher temperature .. ,,_ ~ ... ,~.

~ t may be used with plastics having a higher softening point such as polypropylene. At lower temperatures the hold time is quite long. Fore example, at 160F 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 90F to 105F. This temperature is desirable as it will quickly evaporate off any excess moisture adhering to the carton.
The temperature of the cooling water may be about 35F to 60F. The cartons then leave the processor and are packed in cases.
The process is further illustrated by the following examples:
Exam~le 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 Brie (%
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 70F 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 167F in 14 minutes and held at that temperature for 10 minutes.

-- 21a -They are then chilled with water at 40F for 12 minutes to give an exit temperature of 90F. 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 10 This example relates to a tomato and claim 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 ~~ - 22 - 133 6147 of monosodium glutamate; 700 Ibs of glucose solids; 30 lbs of spices and 10 gal. of clam broth. It is pumped to a pa steurizer where the product is brought to a temperature of 250F in about 10-20 seconds, and held at this temperature to 48 5 to 52 seconds, cooled at 70F 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 pa steurized at a conventional UHT temperature such as 250 F
10 for approximately 8 seconds then immediately cooled to ambient temperature. The milk is then cold filled into gable top cartons in the normal manner under stringent sanitary conditions and then sealed and processed as described in Example 1.

Claims (62)

1. A method of shelf stable packaging a perishable 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 thermoplastic 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 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 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 outwardly 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 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 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 pasteurization hold temperature is in the range of 160°F to 174°F.

12. A method as in claim 1, in which the thermoplastic 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 if 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 food 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, both said side flaps and said end flaps each having upper portions and lower portions, 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 maintained 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; and, 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; and, wherein the sealed carton and perishable product are then heated to a pasteurization hold temperature, maintained at the pasteurization 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 pasteurization 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 and to oppose side flaps to soften the thermo-plastic layer so that the opposed flaps adhere to each other and the end flaps adhere to the lower portions of the side flaps and applying less pressure to an area at the center 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 food product, the carton having a surface layer which softens at a predetermined 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, said side flaps having lower portions and said end flaps having upper portions, 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 portions 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 pasteurization 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 package according to claim 25, wherein said surface layer softens at a predetermined softening temperature; said heating in c) is to a temperature below the softening temperature of the surface layer of the gable top carton material; said maintaining in d) is sufficient for storing said food product; and the cooling in e) is such that by filling the carton with product and then sealing the carton before the product is heated, no significant vacuum is created in the course of cooling the product.

27. A carton and product contained therein, according to claim 23, wherein the cold filling of the product into the carton before sealing of the carton is effective to avoid creation of a vacuum within the carton.

28. A carton according to claim 16, 17, 18 or 19, wherein said strongly sealed area includes at least a centrally disposed portion of the side flaps.

29. A gable top carton as in claim 16, 17, 18, 19, 20 or 21, comprising a carton body and said gable closure, said closure being openable to form a pouring spout having a tip, said fold lines, including a horizontal fold line, to facilitate said closing and opening, the fold lines on at least one end panel intersecting at a point corresponding to said tip of the pouring spout from which the end panels extend, the closure being sealed by forming a seal across the flaps including a center stake located above a point midway between an upper edge of the end flaps and the horizontal fold line such that the carton is hermetically sealed and so that said first lightly sealed area of the flaps is immediately adjacent the intersection of the fold lines and during opening, this area will pop out to facilitate opening of the carton.

30. A gable top carton of claim 29, 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 form said lightly sealed area at a central region 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.

31. A gable top container according to claim 16, comprising a container body and said gable top closure, said upper portions of said end flaps terminating in an upper edge, 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 that 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 central portions of the end flaps, the gap being sealed from approximately the center of its vertical extent to at least the upper edges of the end flaps, and the gap being substantially unsealed below the center of its vertical extent.

32. A gable top carton according to claim 16, said side flaps and said end flaps terminating in upper edges and a lower edge of each of said side flaps and end flaps being defined by a horizontal fold line wherein the side panels splay to form the top of the carton, each end flap having a central vertical fold line to permit inward folding of the end flap so that the inner faces of the end flaps contact adjacent inner faces of the side flaps when the gable top is closed, and each of the flaps having an upper edge, the upper edges of the side flaps extending beyond the upper edges of the end flaps, one of the end flaps being outwardly foldable to form a spout;
a first level of sealing along a horizontal stake line above and closely adjacent to the upper edges of the end flaps, along at least one vertical stake line extending from the lower edges of the side flaps to intersect the horizontal stake line near one end of the horizontal stake line, and over a first central region covering a portion of the vertical fold lines of both end flaps extending downwards from the upper edges of the end flaps but not so far as to include the area at which the vertical fold lines and the horizontal fold lines intersect;
lesser levels of sealing at a second central region covering a portion of the vertical fold lines of both end flaps not covered by the first central region and to any remaining portions of the side flaps wherein the seals provided by the first level of sealing and the lesser levels of sealing are together sufficient to prevent bacteria and air from entering the carton through the sealing flaps, but which said lesser levels of sealing applied across the end flaps would not themselves provide seals sufficient to prevent bacteria and air from entering the carton through the sealing flaps if applied across the entire sealing flaps, and wherein the carton so sealed by the first level of sealing and the lesser levels of sealing is easier to open than a carton in which all of the sealed portions have been sealed with the first level of sealing.

33. A gable top carton as in claim 16, wherein said side flaps and said end flaps have upper and lower edges 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 edges of the side flaps extending beyond the upper edges of the end flaps, said end flaps being inwardly folded towards each other to most closely face one another in the area of the center of the lateral extend of the side flaps, one set of said end flaps being outwardly foldable to form a spout;
a first set of seals that are located at predetermined portions of the sealing flaps, said sealed predetermined portions including:
i) a horizontal stake line extending the full length of the side flaps at a level just above the upper edges of the end flaps;
ii) at least one vertical stake line located inwardly of at least one end of the flaps extending downward from the horizontal stake line to the horizontal fold line;
iii) a center stake located at the central portion of the side flaps in the area where the inwardly folded end flaps face each other, said center stake being of a size and shape sufficient to cover portions of both the end flaps and being located above the horizontal fold lines, said stake lines and center stake being configures and positioned and said first set of seals at said stake lines and said center stake being sufficient to create hermetic seals at these portions of said sealing flaps; and a second set of lighter seals at other portions of the sealing flaps, said second set of lighter seals being sufficient to provide a seal at these other portions that in combination with the sealing provided at the stake lines and at the center stake results in an overall hermetic seal which prevents bacteria and air from entering the carton through the sealing flaps, but which said second set of seals, if applied alone across both said predetermined portions and said other portions of the sealing flaps would not provide a seal sufficient to prevent bacteria and air from entering the carton through the sealing flaps, thereby providing a carton that is easier to open than a carton in which all of the sealed portions of the sealing flaps have been closed with seals that are as strong as those of the first set of seals.

34. The carton of claim 33, in which the said other portions over which said lighter seals are applied include 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 toward the spout end of the carton.

35. The carton of claim 34, in which the first area is in the shape of a triangle tapering towards the spout end of the carton.

36. The carton of claim 34, 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.

37. The carton of claim 34, in which the strength of the seals 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.

38. The carton of claim 33, in which the said other portions over which lighter seals are applied include an 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.

39. The carton of claim 38, in which the strength of the seal over the area to which lighter degree of sealing is applied is relieved progressively from the horizontal stake line down.

40. The carton of claim 33, 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.

41. The carton as in claim 32, in which the sealing flaps include:
a) 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, b) the strength of the applied seal is further relieved over a first area between the upper edge of the end flap that is outwardly fold-able to form a spout and the horizontal fold lines, which area extends from the general area of the center stake outwardly approximately one third the distance toward the spout of the carton; and c) sealing strength is progressively further relieved from the horizontal stake line down over a second area extending below the upper edge of the end flap that is foldable to form a spout and centered approximately two thirds of the way between the center stake and the vertical stake on the spout side of the carton.

42. A method of shelf stable packaging a perishable 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 sequential steps of:
a) ensuring that said 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 containing said liquid food product at substantially room temperature by applying heat and a first predetermined amount of pressure to predeter-mined portions of the sealing flaps, said predetermined portions including:
i) a horizontal stake line extending the full length of the side flaps at a level just above the upper edge of the end flaps;
ii) at least one vertical stake line located inwardly of at least one end of the flaps extending downward from the horizontal stake line to the horizontal fold line;
iii) a center stake located at the central portion of the side flaps in the vicinity of the junction of the inwardly folded end flaps, said center stake being of a size and shape sufficient to cover portions of both the end flaps and being located above the horizontal fold line, said stake lines and center stake being configured and positioned and said first predetermined amount of pressure and heat applied to said stake lines and said center stake being sufficient to create hermetic seals at these portions of said sealing flaps, and applying lesser amounts of pressure to other portions of the sealing flaps, said lesser amounts of pressure being sufficient to provide a seal at these other portions that in combination with the seal provided at the stake lines and at the center stake results in an overall hermetic seal which prevents bacteria and air from entering the carton through the sealing flaps, but which said lesser amounts of pressure, if applied across both said pre-determined portions and said other portions of the sealing flaps would not provide a seal sufficient to prevent bacteria and air from entering the carton through the sealing flaps;
wherein the overall effect is to provide a carton that is easier to open than a carton in which all of the sealed portions of the sealing flaps have been sealed with the first predetermined amount of pressure;
d) heating the food product in the sealed carton to a temperature sufficient for pasteurization but below the softening temperature of the thermoplastic coating;
e) maintaining the food product at the pasteurization temperature for sufficient time to kill essentially all microorganisms remaining within the sealed carton; and f) cooling the gable top carton and its pasteurized contents.

43. A method as in claim 42, in which the said other portions over which less pressure is applied include 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 toward the spout end of the carton.

44. A method as in claim 43, in which the first area is in the shape of a triangle tapering towards the spout end of the carton.

45. A method as in claim 43, 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.

46. A method as in claim 43, 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.

47. A method as in claim 42, in which the said other portions over which less pressure is applied include an 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

48. A method as in claim 47, in which the pressure over the area to which less pressure is applied is relieved progressively from the horizontal stake line down.

49. A method as in claim 42, 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.

50. A method as in claim 42, in which the predetermined portions of the sealing flaps include:
a) 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 b) 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 c) 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.

51. A method as in claim 42, in which the pasteurization hold temperature is in the range of 160°F to 174°F.

52. A method as in claim 42, in which the thermoplastic is polyethylene and the pasteurization hold temperature is in the range of 106°F to 174°F.

53. A method as in claim 42, in which the pasteurization hold temperature is about 167°F.

54. A method as in claim 42, in which the food product is maintained at a pasteurization hold temperature of about 167°F for about 10 minutes.

55. A method as in claim 42, in which after pasteurization the food product is cooled by chilled water to a temperature of about 90°F to 105°F.

56. A process for packaging a perishable liquid product free from pathogenic and thermophilic organisms in a shelf stable gable top carton which includes sealing flaps which comprise side flaps and inwardly folded end flaps, one set of which end flaps is outwardly foldable to form a spout, the process comprising the sequential steps of:
a) cold filling the gable top carton with the product;
b) hermetically sealing the carton containing said liquid food product at substantially room temperature by applying a first predetermined amount of pressure to predetermined portions of the sealing flaps that is sufficient to create hermetic seals at these predetermined portions of said sealing flaps, and applying lesser amounts of pressure to other portions of the sealing flaps, said lesser amounts of pressure being sufficient to provide a seal at these other portions of the sealing flaps that in combination with the seal provided by the first predeter-mined amount of pressure results in an overall hermetic seal which prevents bacterial from entering the carton through said sealing flaps, but which lesser amounts of pressure would not alone be sufficient to prevent bacteria from entering the carton through the sealing flaps if applied across the entire sealing flaps, wherein the carton is easier to open than a carton in which all of the sealed portions of the sealing flaps have been sealed with the first predetermined amount of pressure;
c) heating the product in the sealed carton to a pasteurization hold temperature which is above the pasteurization temperature of the product;
d) maintaining the food product at the pasteurization hold temperature for sufficient time to provide an adequate kill of microorganisms in the sealed carton; and e) cooling the pasteurized product within the carton so that by filling the carton with product and then sealing the carton before the product is heated, no significant vacuum is created in the course of cooling the product.

57. A method of shelf stable packaging a perishable 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 sequential steps of:
a) ensuring that said 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) closing the carton so that the sealing flaps are adjacent one another;
d) hermetically sealing the carton containing said liquid food product at substantially room temperature by applying heat and a first level of pressure to first portions of the sealing flaps that is sufficient to create hermetic seals at these portions of said sealing flaps, and applying lesser levels of pressure to other portions of the sealing flaps, said lesser levels of pressure being sufficient to provide a seal at these other portions of the sealing flaps that in combination with the seal provided by the first level of pressure results in an overall seal which prevents bacteria from entering the carton through the sealing flaps, but which lesser levels of pressure would not alone be sufficient to prevent bacterial from entering the carton through the sealing flaps if applied to both said first portions and said other portions of the sealing flaps, wherein the carton is easier to open than a carton in which all of the sealed portions of the sealing flaps have been sealed with the first level of pressure;
e) heating the food product in the sealed carton to a temperature sufficient for pasteurization but below the softening temperature of the thermo-plastic coating;
f) maintaining the food product at the pasteurization temperature for sufficient time to kill essentially all microorganisms remaining within the sealed carton; and g) cooling the gable top carton and its pasteurized contents to provide a shelf stable food product in a carton free from significant internal vacuum.

58. A method as in claim 57, wherein the liquid food product contains no artificial preservatives.

59. A method as in claim 58, wherein the liquid food product remains shelf stable without refrigeration for at least three months.

60. A method as in claim 57, wherein the temperature of the liquid food product at the time of filling into the carton is in the range of 60°-80°F.

61. A method as in claim 57, wherein the liquid food product is filled into the carton that is open to the environment.

62. A method of shelf stable packaging a perishable liquid food product in a four-sided carton having a gable top which is internally coated with thermoplastic and which includes sealing flaps comprising two opposed side panels terminating in upper side flaps and two opposed end panels terminating in inwardly foldable upper end flaps, a lower edge of each of said side flaps and end flaps being defined by a horizontal fold line wherein the side panels splay to form the top of the carton, each end flap having a central vertical fold line to permit inward folding of the end flap so that the inner faces of the end flaps contact adjacent inner faces of the side flaps when the gable top is closed, and each of the flaps having an upper edge, the upper edges of the side flaps extending beyond the upper edges of the end flaps, one of the end flaps being outwardly foldable to form a spout, the method comprising the steps in sequence of:
a) ensuring that the liquid food product is free from pathogenic and thermophilic organisms;
b) filing the carton with the liquid food product maintained at substantially room temperature;
c) closing the gable top containing said liquid food product while the liquid food product is at ambient temperature by inwardly folding each end flap so that the inner surfaces of the side flaps abut the adjacent inner surfaces of the end flaps;
d) hermetically sealing the carton by applying heat and at least a predetermined first pressure to the side flaps that is sufficient to provide a hermetic seal along a horizontal stake line above and closely adjacent to the upper edges of the end flaps, along at least one vertical stake line extending from the lower edges of the side flaps to inter-sect the horizontal stake line near one end of the horizontal stake line, and over a first central region covering a portion of the vertical fold lines of both end flaps extending downwards from the upper edge of the end flaps but not so far as to include the area at the intersection of the vertical fold lines and the horizontal fold lines, and applying lesser amounts of pressure to a second central region covering a portion of the vertical fold lines of both end flaps not covered by the first central region and to any remaining portions of the side flaps wherein the seals provided by the predetermined first pressure and the lesser amounts of pressure are together sufficient to prevent bacteria and air from entering the carton through the sealing flaps, but which said lesser amounts of pressure applied across the end flaps would not themselves provide seals sufficient to prevent bacteria and air from entering the carton through the sealing flaps if applied across the entire sealing flaps, and wherein the carton so sealed by application of the predetermined first pressure and the lesser amounts of pressure is easier to open than a carton in which all of the sealed portions have been sealed with the first pre-determined amount of pressure;
e) heating the food product in the sealed carton to a temperature sufficient for pasteurization but below the softening temperature of the thermo-plastic coating;
f) maintaining the food product at the pasteurization temperature for sufficient time to kill essentially all microorganisms remaining within the carton; and g) cooling the gable top carton and its pasteurized contents.