IE890785L - Method of providing shelf stable liquid food products and a container for use therein - Google Patents

Abstract

This invention is concerned with the [AP107A]

Description

6251 0 This invention relates to a method of providing liquid food products that are shelf stable.

Liquid food products include all fruit, juices, drinks, blends of juices in drinks with or without preservatives. 5 Examples are citrus products, such as orange juice and citrus flavoured products with or without preservatives such as sodium benzoate or potassium sorbate, fruit products such as grape, apple or strawberry drinks or juices, vegetable juices and vegetable cocktails. Liquid food products also include dairy 10 products such as milk. Liquid food products include sauces, puddings, custards, syrups and soups. Included also are low alcohol, non-carbonated products such as citrus wine coolers.

A variety of containers have been used including cans, glass, plastic and paperboard cartons.

Although containers of plastic and paperboard are generally less costly than glass containers or cans, there has been a problem of providing plastic or paperboard containers that have adequate shelf life without refrigeration.

Liquid food products are treated in various ways to render 20 them free from microbial contaminants such as yeast, mould and bacteria. If products after treatment still contain any of these organisms, spoilage will soon occur. Even if the microorganisms that are in juices or other drinks are controlled by methods such as pasteurization, microwaves or gamma rays, there is the danger 25 of contamination from the atmosphere or from the empty container during filling.

One method of treatment that is commonly used may be called the "hot fill" method. The product is typically pasteurized at about 195'F and then filled into containers at 180*F. to 190"F., 30 then the filled containers are sealed, inverted to sterilize the lid with the hot product and cooled to ambient temperatures. Although the hot fill method is widely used it has disadvantages. Specially designed and costly containers are needed because of the temperature at which filling takes place. For example, a six layered carton is commonly used including 5 successive layers of polyethylene, a barrier tie layer, an * aluminum foil barrier, another tie layer, paperboard and polyethylene. The barrier tie layer is needed as otherwise there . will be delamination between the polyethylene and the foil due to high filling temperatures. The temperature of filling is 10 disadvantageous in the case of some products such as orange juice, which rapidly deteriorates due to oxidation at elevated temperatures to cause rapid degradation of flavour. There is a tendency for foaming and splashing to occur. Perhaps the most serious problem is that after cooling there is a vacuum which 15 means that an extremely tight and effective closure must be used, otherwise air will channel into the interior bringing with it microorganisms which will cause the product to deteriorate. For example, if orange juice is filled by the hot fill method into a gable top paperboard container of the type conventional for milk, 20 the adhesive used in milk cartons to secure the top, and which is releasable to form a pouring spout, would be entirely inadequate to cope with the vacuum following hot filling. The main areas where channelling of air and air borne microorganisms would be likely to occur would be at the centre of the gable 2 5 top, or through the sides and down at the centre. If, however, a very strong seal is used to avoid channelling it is difficult or impossible for most consumers to open the gable top to form a pouring spout. The problems of hot filling can be avoided by cold filling The product is pasteurized to 185*- 195"F and 30 cooled for filling to ambient temperatures into a non-sterile package.

The product must be refrigerated at all times and usually has a two week shelf life. Cold filling may also be used if adequate preservatives are present. The product has a ' preservative added to it such as sodium benzoate or potassium sorbate. Drinks are stable for three to six months at room temperature but juices should be kept refrigerated as a preservative only prevents microorganisms from growing, it does not kill them. If the initial content of microbes is too high, the preservative will not be able to stop rapid growth and 5 spoilage will occur. A positive feature of preserved technology is the product can be packed into any container. A negative feature is that preservatives used at less than 500 ppm are ineffective and above this level leave a burning taste in the product.

The most recent technology is known as the "aseptic" method.

It involves the filling of a presterilized product into a presterilized package under a sterile atmosphere. Product is pasteurized up to 195"F for 15 seconds and cooled to ambient temperature for filling. The package is treated with hydrogen 15 peroxide or steam before filling. The filler is in a room held under positive air pressure. Examples of aseptically filled product can be seen with the "Brik" pack and some shelf stable puddings in plastic containers. This is highly complex technology requiring extensive amounts of capital and maintenance 20 expense and is extremely unforgiving in the event of line problems. Line speeds are generally slow.

Although post pasteurization or sterilization after filling and capping has been used in the brewing trade and for some carbonated drinks containing juices, this has involved glass 25 containers or cans. It is believed that no practical process has been developed for post pasteurization where the containers are of plastic or paperboard coated with plastic.

It is an object of invention to utilize post pasteurization techniques to solve problems inherent in the use of plastic or 30 paperboard containers coated with plastic.

It is another object of the invention to provide a gable top container suitable for use in the above method. A still further object of this invention is to provide a gable top carton having a secure seal, but which can easily be opened. 35 In accordance with one aspect of this invention, a method of providing liquid food products that are shelf stable comprises the steps of: (a) cold filling a plastic or plastic coated container with an essentially non-carbonated liquid food product free from pathogenic and thermophilic organisms: 5 (b) sealing said container; & (c) heating the food product in said container to a pasteurization hold temperature in the range of about 160'F » to the softening temperature of the plastic; (d) maintaining the food product at said pasteurization 10 hold temperature for sufficient time to provide adequate kill of essentially all microorganisms in the food product; (e) cooling.

In accordance with another aspect, the invention provides a gable top carton the gable closure of which includes opposed side 15 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 panels and end panels having score lines to facilitate closing and opening, the opposed side flaps being adhered to each other and the end flaps being adhered 20 to the lower portions of the side flaps, characterized in that an unsealed area is left at the centre of upper portion of an end flap to facilitate opening of the carton by a consumer.

The liquid food products to which the method of this invention is applicable include non-carbonated fruit products 25 such as the citrus products or citrus flavored products, fruit products, vegetable juices and vegetable cocktails previously referred to. Carbonation must be avoided as otherwise the pressures that would be generated during the process would be too high. Another requirement of the food product is freedom from 30 pathogenic and thermophilic bacteria. Most juices and drinks have pH's in the range 2. 8 to 4. 0 and not above pH 4. 6. At a pH above 4. 6 there is a potential problem of pathogenic bacteria. Below pH 4. 6 the problems are yeast, moulds and bacteria.

. If the pH is above 4. 6, which would include such products as 35 milk, then there should be a preliminary ultra high temperature treatment at 240'F to 260"F for 15-20 seconds to kill pathogenic organisms, followed by cooling to ambient temperature. A preliminary ultra high temperature treatment is advisable with some vegetable base products such as tomato, due to the initial high content of thermophilic moulds.

The juices and drinks to which this process is applicable are formulated in a tank at ambient temperatures in the range 40"F - 75*F and pretreated as discussed above if necessary. They are then pumped to a filling station where the juice or drink is fed into containers.

Although not essential, it may be useful to provide a sparging infusion valve in the line between the tank and filling station. The sparging infusion valve is used to add up to about 0. 1 lbs/square inch of nitrogen or carbon dioxide, and preferably about 0.01 lbs/square inch. The purpose of sparging is to create 15 a slight positive pressure to oppose the entrance of any bacteria into the container after filling.

Carbon dioxide is preferred for this purpose. The product sparged with carbon dioxide would have such a small amount of carbon dioxide that it would not be classified as a carbonated 20 product.

At the filling station which is of conventional type, a number of individual containers are filled cold. The temperature of the liquid food product should be less than about 80'F and desirably less than 7*F to achieve a neutral or positive 25 pressure after filling. This may be contrasted with hot fill temperatures of the order of 180"F. The maximum temperature that can be used depends on the conditions including the positive pressure from any sparging gas and on the strength of the seal, which in some cases might accept a slight vacuum. However, as 30 previously indicated a vacuum is undesirable. After filling and closing the cartons there should be a neutral to slightly positive pressure.

The containers that are preferred are gable top cartons of paperboard having a barrier layer such as foil and a polyethylene 35 layer in the interior of the carton and another polyethylene layer to bond the foil to the paperboard. The exterior of the carton may also be coated with polyethylene to give a total of five layers. A sixth layer, usual for hot filling methods, is not needed. It is not necessary that a strong seal be used, therefore an easy opening gable top container that can be 5 opened to give a pouring spout that is suitable. Although some of the main benefits of this invention are obtained with easy opening gable top containers, other types of containers such as plastic pouches or plastic bottles may be used in accordance with this invention in its broadest aspect. Suitable plastics for 10 the container 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 fill may be substituted for foil. 15 The cold filled cartons are transferred to a processor comprising three zones, a preheat zone, a hold zone, and a cool zone.

The processor may be in the form of a continuously moving chain upon which rows of cartons are placed. The cartons are 20 spaced to allow water to run down the sides of the cartons to heat or cool the contents. 1. Preheat zone The cold filled cartons are preheated preferably by pouring water at a temperature of 180"F to 185'F onto the cartons and allowing 25 it to cascade down the sides. After a period of time that varies with the size of the carton, the liquid product within it reaches the desired "pasteurization hold" temperature. The preferred temperature for "pasteurization hold" is about 167'F, which will be reached in about 1319 minutes in the case of 1 litre cartons. 30 Two litre cartons would take 20 to 24 minutes to reach this temperature, while 4 to 7 minutes would be adequate for 250 ml. cartons. 2. Hold zone.

The product is maintained at the required pasteurization 35 temperature for a predetermined time to ensure adequate kill of all microorganisms. The appropriate time at various "pasteurization hold" temperatures is available from standard texts. At the preferred temperature of 167'F a hold time of ten minutes is recommended. The temperature should not be greater than about 174'F, at which the time will be about' 4 minutes, as 5 otherwise there may be problems with softening of the plastic where the container is polyethylene and delamination of foil from paperboard will occur. Slightly higher temperature may be used with plastics having a higher softening point such as polypropylene. At lower temperatures the hold time is quite long. 10 For example, at 160"F it would be about 25 minutes. 3. Cool zone After holding for the required amount 5 of time, the cartons go into a cooling zone and exit at around 90"F to 105"F. This temperature is desirable as it will quickly evaporate off any 15 excess moisture adhering to the container. The temperature of the cooling water may be about 35*F to 60*F. The cartons then leave the processor and are packed in cases.

This invention is further illustrated by the following examples: Example I This example relates to the production of 1000 Imperial gal. of single strength (ready to drink) orange juice. 135 gal. of orange juice concentrate 65 Brix (% soluble solids) is added to 865 gal. of water and blended for 10 minutes.

It is then pumped using positive pumps through a line 25 leading to a filler. The line includes a sparging infusion valve to sparge carbon dioxide to give an end product with about 0. 1 lbs/square inch of gas. At the filler the carton is filled at a temperature of about 70*F into one litre gable top cartons which are heat sealed under pressure. The cartons are brought up to a 30 temperature of 167*F in 14 minutes and held at that temperature for ten minutes. They are then chilled with water at 40*F for 12 minutes to give an exit temperature of 90*F. The orange juice has a desirable shelf life of three months and a recommended maximum of six months. The taste of the orange juice is markedly 3 5 better than that produced by hot filling.

Example 2 This example relates to a Caesar's clam juice cocktail. A thousand imp.gal. batch was made of 100 imp. gal of tomato paste (32-34 brix); 560 lbs of salt;60 lbs of monosodium glutamate; 700 5 lbs of glucose solids; 30 lbs of spices and 10 gal. of clam broth. It is pumped to a pasteurizer where the product is brought to a temperature of 250*F in about 1020 seconds, and held at this temperature for 48 to 52 seconds, cooled to 70 *F and then filled and processed as described in Example 1.

As mentioned above, the present invention also relates to a gable top carton of improved construction.

Gable top cartons are commonly used for packaging liquid food products such as milk, juices, citrus products and vegetable cocktails. When the product is to be refrigerated, such as in the 15 case of milk, the integrity of the seal is not critical.It is desirable to avoid spillage, but because of the short shelf life and refrigeration of the milk there should not be a practical problem due to spoilage as a result of contaminants entering the carton.

It is therefore possible to provide a closure that can be opened without too much difficulty by the consumer.

Where the product to be packaged is another product such as orange juice or vegetable juice, it is desirable that it have adequate shelf life without the necessity of refrigeration. If 25 the seal is inadequate, bacteria, molds and yeast may contaminate the product and cause spoilage. Also if air enters the container it may cause oxidation.

It is therefore necessary to provide an extremely strong seal. The entire top is heat sealed, according to present 30 practice . and is also impressed with vertical stake lines, a horizontal stake line, and a central stake point. The result is, however, that the container is not an easy opening carton from the point of view of the average consumer.

This defeats one of the main purposes of having a gable top 35 container. Various expedients have been used to try to solve this problem including a weakened severance line, but this has not proven to be entirely satisfactory.

In the drawings which illustrate the preferred embodiment of the container according to this invention: Figure 1 is a perspective view of a gable top container in 5 accordance with this invention; Figure 2 is a perspective view illustrating the opening of the carton shown in Figure 1, with part broken away.

Figure 3 illustrates the carton of Figure 1 that has been opened up to show the areas that have been heat sealed. 10 Figure 4 is an elevation view of a die that may be used for heat sealing the carton of Figures 1 to 3.

Figure 5 is a perspective view of a gable top container in accordance with another embodiment of this invention illustrating the opening of the carton.

Figure 6 is a perspective side elevation view of the male portion of a die for producing the embodiment of Figure 5.

Figure 7 is a perspective side elevation view of the female portion of a die for producing the embodiment of Figure 5.

Referring now to the drawings, the carton illustrated is 20 mainly of conventional construction. It includes opposed pairs of side walls 10 and 11, connected by a fifth panel 12 (shown in Figure 3).

There is a bottom closure 13 and a gable top generally indicated at 14. The gable top includes a pair of side panels 15 25 having score lines 16 to facilitate opening and a pair of end panels 17 having score lines 18. A pair of top flaps 19 are extensions of side panels 15 and extend somewhat higher than flaps 30 that are an extension of end panels 17. Flaps 19 are heat sealed in face to face relationship as shown in Figure 1. 30 Flaps 20 are heat sealed to the interior of the lower parts of flaps 19 as shown in Figure 2. It is usual to provide a pair of stake lines 21 at the end that is not to be opened and which coincides with the fifth panel. At the other end there is static line 21a. There is also a horizontal stake line 22. Stake lines 35 are strongly indented to give a more secure seal. There is also a stake point 23 which presses together, expands into abutment and seals the adjacent edges of the inwardly folded end flaps 17. The foregoing is conventional structure.

The difference from conventional structure according to this invention is in the area of the seal between flap 19 and flap 20.

According to conventional practice in the case of hot fill the whole of the interior of flap 20 is sealed to flaps 19. According to this invention an area preferably in the shape of an inverted triangle is left unsealed at the top centre of flap 20 as indicated by the numeral 25 in the broken away part of Figure 2. 10 The remaining sealed area is cross hatched and indicated at 24.

In Figure 3 the unsealed 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 there is the location of stake point 23 at the apex of triangle 25, an effective seal is 15 provided in spite of this unsealed area. The unsealed area at the top centre 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.

Figure 4 illustrates the male jaw of a suitable die 30 20 including die face portion 31 for pressing together the upper part of flaps 19, die face portions 32 and 33 for the ends and horizontal stake embossing lines 34, vertical stake embossing lines 34 and embossing protrusion 36 for the stake point. Die face portion 37 which connect flaps 19 and 20 is cut away at 38 25 to leave a triangular unsealed area. This can be used with a matching female die.

Alternatives for providing the desired unsealed area would include the use of silicone as a parting agent to prevent adhesion in area 25. Another possibility if adhesive were used in 30 place of heat sealing would be to omit adhesive in area . Heat sealing is however the preferred method of closure where the carton is coated with a thermoplastic resin. The preferred structural material is in five layers, namely, an inner coating of polyethylene to bond the foil, a layer of paper board 35 and an outer layer of polyethylene. Other thermoplastic coatings could be used of the type acceptable with food products, such as vinyl resins, e. g. , polyvinyl chloride.

Figure 5 of the drawings illustrates an 3 5 improved structure which is similar to that illustrated in Figures 1 to 4 but showing an unsealed or lightly sealed area at the top of flap 5 20 immediately above stake point 23 substantially in the shape of a rectangle 25A instead of the triangle of Figure 2 and showing a ) further unsealed or lightly sealed area 25B extending between stake point 23 and stake line 21a. Areas 25A and 25B are left unsealed or are lightly sealed by providing a die which applies 10 no pressure or little pressure in these areas.

The construction of a suitable die 10 is illustrated in Figure 6 showing male jaw 40 and Figure 7 showing female jaw 41. Referring now to Figure 7, male jaw 40 has a die face 42 having a raised longitudinal rib 43 to provide a horizontal stake and 15 vertical ribs 44 and 45 to provide stake lines on the side of the container that is to remain sealed and a vertical rib 46 to provide a stake line on the side of the container that is to be opened. Male jaw 40 has a set screw 47 to provide a central stake point 23. The generally rectangular relieved area 25A of Figure 5 20 is provided by depressed area 48 immediately above set screw 47 and offset in the direction of the side of the carton that is to be opened. A relieved area 49 is also provided extending from set screw 47, which provides stake point 23 to web 46 which provides stake line 21a. Male jaw 40 also includes area 50 for sealing top 25 flaps 19 of the container and areas 51, 52, 53 and 54 for sealing the remainder of flaps 20.

Female die 41 shown in Figure 7 has 30 an upper area 55 which mates with portion 50 of the male jaw and a slightly undercut area 51 the upper edge of which is located to 30 accommodate rib 43. Die 41 has slots 56 and 57 to accommodate webs 44 and 45 and slot 58 to accommodate web 46. It also has a depressed area 59, to relieve pressure, matching area 49 of the male die and generally rectangular pressure relieving area 60 matching area 48 of the male die.

Claims (27)

1. A gable top carton, the gable closure of which includes opposed side panels with side flaps extending therefrom and opposed end panels 5 with end flaps extending therefrom to a lower height than the flaps of the side panels, said side panels and end panels having score lines to facilitate closing and opening, the opposed side flaps being adhered together and the end 10 flaps being inwardly folded and adhered to the lower portion of the side flaps, the inner surface of the carton being coated with thermoplastic material and the sealing up of the carton being accomplished by heat sealing to leave an unsealed or 15 lightly sealed area at the centre of the upper portion of an end flap to facilitate opening of the carton by a consumer characterized in that there is a stake point impressed in the side flaps which presses together, expands into abutment and seals 2o the adjacent inwardly folded end flaps.

2. A gable top carton as in claim 1, in which the stake point is immediately below the unsealed or lightly sealed area.

3. A gable top carton as in claims 1 or 2, 2 5 having a horizontal stake line impressed "in the side flaps in register with the tops of the inwardly folded end flaps.

4. A gable top carton as in claims 1, 2 or 3, in which there are vertical stake lines at each end of the side flaps. -13-

5. A gable top carton as in claim 4, in which there is a further unsealed or lightly sealed area extending along the lower portion of the end flap from substantially the centre to the closed 5 vertical stake lines .

6. A gable top container as in any of claims 1 to 5, containing a shelf stable non-carbonated liquid food product, preferably citrus juice, free from preservatives, and which does not require an 1o artificially cooled storage environment and which container is free from significant internal vacuum.

7. A gable top container as in claim 6, the contents of which remains shelf stable for at least three months. 15

8. A gable top container as in claim 7, the contents of which is a citrus juice having an improved taste as compared with the product of a hot fill method.

9. A gable top container as claimed in claim 1, 2o substantially as hereinbefore described with particular reference to and as illustrated in the accompanying drawings. A method of providing liquid food products shelf stable comprising the steps of: (a) cold filling a plastic or plastic coated easy opening gable top container with a non-carbonated liquid food product free from pathogenic and thermophilic organisms; (b) sealing said container; (c) heating the food product in said container to a pasteurization hold temp- 25 30

10. that are -1 4- erature in the range of about 71 °C (160°F) to the softening temperature of the plastic; (d) maintaining the food product at said pasteurization hold temperature to pasteurize the food product; (e) cooling to provide a liquid food product in any easy opening gable top container that can be opened by hand to give a pouring spout, said liquid product being free from the vacuum condition associated with hot filling.

11. A method as in claim 10, in which the liquid food product is selected from fruit products and vegetable juices. 15

12. A method as in claim 11, in which the liquid food product is orange juice and the pasteurization hold temperature is in the range of 71°C (160°F) to 79°C (174°F).

13. A method as in claim 11, in which the liquid 2 0 food product is a clam tomato product.

14. A method as in claims 10, 11 or 12, in which the plastic or plastic coating is polyethylene and the pasteurization hold temperature is in the range 71°C (160°F) to 79°C (174°F). 25

15. A method as in claim 11, in which the liquid food product is essentially free from artificial preservatives.

16. A method as in claim 15, in which the liquid food product has a shelf life of at least three months. 5 1 0

17. A method as in claims 10, 11 or 12, in whicn cold filling is at a temperature below 27°C (80°F).

18. A method as in claims 10, 11 or 12, in which the pasteurization hold temperature is about 75°C 5 (167°F).

19. A method as in claims 10, 11 or 12, in which the pasteurization hold temperature is about 75°C (167°F) and the time at the temperature is about 10 minutes. 10

20. A method as in claims 10, 11 or 12, in which after pasteurization, cooling is to about 32°C (90°F) to 40°C (105°F).

21. A method as in claim 16, in which the liquid food product is citrus juice. 15

22. A method as in claim 10, in which cold filling is conducted under ambient atmospheric conditions.

23. A method as in claims 10, 11 or 12, including the preliminary step of ultra high temperature 20 treatment to kill any pathogenic or thermophilic organisms followed by cooling.

24. A method as in claim 10, in which the pH of the liquid food product is in the range 3.0 to 4.6.

25. A method as in claim 10, in which the food 25 product is non-alcoholic or has low alcohol. -16-

26. A method according to claim 10, substantially as hereinbefore described and exemplified.

27. Liquid food products that are shelf stable whenever prepared by a method claimed in a preceding claim. F. R. KELLY & CO. , AGENTS FOR THE APPLICANTS.