GB2322785A

GB2322785A - Pasteurizing process for filled plastic bottles

Info

Publication number: GB2322785A
Application number: GB9704859A
Authority: GB
Inventors: Geoffrey Alan Giles
Original assignee: SmithKline Beecham Ltd
Current assignee: SmithKline Beecham Ltd
Priority date: 1997-03-08
Filing date: 1997-03-08
Publication date: 1998-09-09
Anticipated expiration: 2017-03-08
Also published as: GB9704859D0; GB2322785B

Abstract

A process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region, in which the containers are transported on a conveyor line in a horizontal orientation through a heating region in which the containers are subjected to a stream of heating fluid, such that the temperature of the container increases most rapidly in its body region rather than in its neck region and/or base region. By this process thermal stresses in the containers and cold spots in the contents are avoided. The containers may be made from polyethylene terephthalate.

Description

Pasteurizing Process This invention relates to heat treatment processes and apparatus for products in containers, particularly to pasteurizing processes and apparatus for food products such as drinks contained in bottles.

Food products such as drinks are frequently subjected to a process of pasteurization. This process is normally carried out after they are sealed in the containers in which they are to be stored before and after purchase, to destroy microorganisms which might otherwise cause degradation and contamination.

Such food products are often contained in glass bottles sealed with a closure such as a crimped or screw cap. The generally used process for pasteurizing these filled glass bottles is to convey them in a vertical orientation on a conveyor line, and to pass the bottles under a shower of hot water.

This process is generally suitable for glass bottles. There is a move toward replacement of glass bottles with bottles made of plastics materials, particularly polyethylene terephthalate ("PET") which is a transparent, robust material.

Unfortunately PET suffers from the disadvantage of being vulnerable to distortion and thermal stresses on heating, particularly uneven heating. Bottles generally have an upper neck region defining a mouth opening and a shoulder region in which the sectional shape of the container tapers from a lower wider body region toward the narrower neck region.

For the pasteurization of products contained in bottles, present pasteurization processes involving a vertical orientation of the bottles can be unsuitable. In a vertical orientation, under a shower of hot water the hot water first contacts the bottle at its neck and shoulder region, and the contact of the heated water firstly with the upper part of the bottle, around the neck and shoulder, can result in uneven heating of the bottle and its contents. In a PET bottle this neck and shoulder region, and also the base, is the part of the bottle which is mostly amorphous, unlike the main body which is strain crystallised and normally more stable to thermal stresses than the neck, shoulder and base. Consequently the neck and shoulder region is particularly vulnerable to distortion when the bottle is subsequently heated during the pasteurization procedure. This can cause distortion of the bottle. Distortion is a particular problem if the contents are carbonated, e.g. effervescent drinks, as high internal pressures can be generated.

Regardless of the construction material of the bottle cold spots in the lower part of the contents can occur which are thus not fully pasteurised, as the upper parts of the bottle are heated first. Also whilst such cold spots are coming up to a temperature sufficient for the heat treatment process to which they are to be subjected, e.g. to pasteurise the contents, other parts of the contents are liable to be overheated, which may damage the contents.

It is an object of this invention to provide an alternative procedure for pasteurizing the contents of bottles, particularly plastics material (especially PET) bottles, which in part at least provides a solution to this problem. It is also an object of this invention to provide an apparatus for carrying out this process.

According to one aspect of this invention a process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region is provided, characterised in that the containers are transported on a conveyor line in an orientation which is substantially horizontal, through a heating region in which the containerss are subjected to a stream of heating fluid, in a manner such that the temperature of the container increases most rapidly in its body region rather than in its neck region and/or base region, and/or that the container experiences its maximum temperature in its body region rather than at its neck and/or base region.

According to an alternative aspect of this invention, a process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region is provided, characterised in that the containers are transported on a conveyor line in an orientation which is substantially horizontal, through a heating region in which the containers are subjected to a stream of heating fluid, the heating fluid being directed into contact with the containers in such a way that the bulk of the heating fluid first contacts the body region of the container rather than the neck and/or the base region of the container.

The invention also provides an apparatus for carrying out the process of this invention.

According, therefore, to another aspect of this invention an apparatus for heat treating containers which have an upper neck region defining a mouth opening and a lower wider body region is provided, characterised by a conveyor line on which the containers are transported in an orientation which is substantially horizontal; a heating region through which the containers are transported by the conveyor line and in which the containers are subjected to a stream of heating fluid; the manner of subjection of the containers to the heating fluid in the heating region being such that the temperature of the container increases most rapidly in its body region rather than in its neck and/or base region, and/or that the container experiences its maximum temperature in its body region rather than at its neck and/or base region.

According to an alternative aspect of this invention, an apparatus for heat treating containers which have an upper neck region defining a mouth opening and a lower wider body region, is provided, characterised by a conveyor line on which the containers are transported in an orientation which is substantially horizontal; a heating region through which the containers are transported by the conveyor line; and means to subject the containers to a stream of heating fluid in the heating region, in which the heating fluid is directed into contact with the containers in such a way that the bulk of the heating fluid first contacts the body region of the container rather than the neck and/or the base region of the container.

The term "substantially horizontal" used herein includes orientations in which the neck-base axis of the container is horizontal, and also orientations of the bottle in which the said axis is between +450, preferably i30 of horizontal, more preferably between + 15" of horizontal.

In the process and apparatus of this invention the containers may be bottles which have an upper neck region defining a mouth opening and a shoulder region in which the sectional shape of the bottle tapers from a lower wider body region toward the narrower neck region. With such bottles, in the process and apparatus the temperature of the bottles may increase most rapidly in their body region rather than in their neck and shoulder region and/or base region of the bottle, and/or that the bottles may experience their maximum temperature in their body region rather than at their neck or shoulder and/or base region. This may be achieved by the bulk of the heating fluid first contacting the body region of the bottle rather than the neck and shoulder and/or the base region of the bottle.

As a result of this invention the neck, (and shoulder if present) and/or the base region of the container are not subjected to as rapid a rate of heating as the body region. The neck and shoulder region need not experience direct contact with the high temperature heating fluid that is needed for pasteurization of the contents that is experienced by the body of the container. Also as the contents of the container are in contact with the neck and shoulder and/or base the contents can act as a heat sink ensuring that these regions are not overheated. This solves to some extent the problem with heat treatment of bottles made of plastics materials such as PET bottles outlined above of the prior art processes, in that the amorphous neck, shoulder and base of the bottle are less prone to thermal stresses and distortion as a result of the invention.

A further advantage of the invention is that the heating fluid initially contacts a larger surface area of the container, i.e. about the wide body of the container, than with prior art processes in which the heating fluid is directed at the neck, and shoulder region if present, of an upright container and consequently contacts these regions first. This initial contact of the heating fluid with the wide body can result in more effective transfer of heat to the contents of the container, with consequent more rapid heating, and also avoidance of the problem of formation of cold spots whilst other parts of the contents are overheated. This is advantageous for containers regardless of the materials of which they are made.

The process and apparatus of the invention is suitable for containers generally which have an upper neck region defining a mouth opening and a shoulder region in which the sectional shape of the container tapers from a lower wider body region toward the narrower neck region, and is particularly suitable for bottles, especially plastics material bottles as described above for example made of moulded PET.

The heating fluid may preferably be a stream of hot water e.g. at ca. 75"C, used at substantially the same temperature as in prior art processes. Alternatively other heating fluids may be used, for example hot air. A suitable temperature and flow rate etc. For any particular application can be easily determined by experiment. Typically 20 minutes warm up, followed by 20 minutes maintained high temperature, followed by 20 minutes cooling down is suitable in a process for pasteurising food products such as drinks.

The conveyor line may be of any known type which is suitable for use in the environment of a pasteurizing system, i.e. being capable of withstanding heat and moisture, and will be provided with holders of a suitable shape, size and construction to safely and reliably convey containers such as bottles in their horizontal orientation. The conveyor line is preferably constructed such that the containers are conveyed through the heating zone with their neck-base axis substantially perpendicular to the direction of motion of the conveyor line i.e.

across the length of the conveyor line. This orientation facilitates the mounting of the containers on the conveyor line and also enables more containers to be transported per unit length of the conveyor line.

The conveyor line may be of a mechanically driven conventional type as used at present for the transport of bottles, and similarly the heating and cooling regions may be generally of a conventional nature, adapted to the dimensions and orientation of the conveyor line and the bottles.

The conveyor line may also include baffles and other guides to direct the heating fluid toward the body of the container, and away from the neck and shoulder and/or base region of the container, such as a bottle. Such baffles may be in the form of partitions separating the general region of the body from the neck, and shoulder, and/or the base of the container. In a conveyor line in which the containers are oriented with their neck-base across the conveyor line such baffles and guides may conveniently comprise partitions aligned parallel to the length of the conveyor line.

Additionally or alternatively fluid-directing nozzles or sprays etc. may be used to direct the heating fluid, such as hot water, preferentially onto the body of the container and away from the neck, and shoulder, and/or base region of the container.

Preferably the containers are also caused to rock as they travel on the conveyor line through the heating region, so that the neck and base pivot about a point intermediate in the height of the container between the neck and base as they travel on the conveyor line through the heating region, so as to further assist mixing of the contents. This may conveniently be achieved in a construction in which the containers are oriented with their neck-base axis across the conveyor line, which may be achieved by means which will be apparent to those skilled in the art. For example the conveyor line may be flexible, e.g. constructed of a chain of linked units, and may have an undulating surface in the region where it passes through the heating region.

The containers may also be caused to rotate about their neck-base axis as they travel on the conveyor line through the heating region. This encourages mixing of the contents of the container during heating so as to ensure thorough pasteurization, and also ensures that all areas of the inside of the container are contacted by the hot contents so that contaminant microorganisms on all areas of the internal surface of the container are destroyed. The direction of rotation may reverse at different parts of the conveyor line, to encourage thorough mixing of the contents. Methods of causing a container to rotate in this way will be apparent to those skilled in the art, and the holders may hold the containers in such a way that the containers are free to rotate in the holders. A suitable system to cause such axial rotation is tangential engagement of the surfaces of a cylindrical container such as a bottle with friction surfaces.

After passing through the heating region the conveyor line may carry the containers into a cooling region where they may be allowed to cool to ambient temperature, if necessary aided by contacting the containers with a cooling fluid, such as relatively cold air or water. By maintaining the containers in a substantially horizontal orientation as described above, and optionally rocking and rotating the containers as described above the cooling of the containers and their contents may be facilitated for the same reasons as outlined above for heating, mutatis mutandis, i.e. improved mixing of the contents etc. Also distortion of containers such as plastics material, e.g. PET, bottles under the thermal stress they experience during cooling may be reduced by the invention.

Consequently, therefore in a preferred embodiment of the invention the entire transport of the containers on the conveyer line through the heating and cooling regions may take place with the containers in the same orientation and on the same conveyor line.

The process of the invention is suitable for heat treatment processes such as pasteurisation or sterilisation of all types of contained, e.g. bottled products which are heat treated in conventional process which involve transport of containers such as bottles on a conveyor line through a heating region and optionally a subsequent cooling region. Such products may include food products, e.g. drinks such as fruitjuice based drinks, which may be carbonated, medical products etc. Similarly the process is suitable for the heat treatment of all types of plastics bottles which are intended for heat treatment, but is in particular intended for bottles made of PET.

The invention will now be described by way of example only with reference to the accompanying drawings which show: Fig. 1 A comparative view of a prior art process for pasteurising the contents of bottles.

Fig. 2 A perspective view of a conveyor line according to this invention.

Fig. 3 A cross section through the conveyor line of Fig. 1 at three positions (a), (b) and (c) progressively sequentially along the direction of transport.

Referring to Fig. 1 a prior art process for pasteurising the contents of bottles is shown schematically. A bottle 1 generally comprises a body region 2, a neck region 3 defining a mouth closed with a cap and a shoulder region 4 in which the wider section of the body 2 tapers toward the narrower section of the neck 3. The bottle is mounted with its base 5 on a conveyor line (not shown) with a vertical orientation of the neck-base axis.

The bottle may be made of blow-moulded PET. As a consequence of this manufacturing process the body region 2 is straincrystallised, whereas the neck 3, shoulder 4 and base 5 are of amorphous PET. The bottle contains a liquid content to be pasteurised, such as a fruit juice concentrate or glucose drink.

During the pasteurisation process, a stream of hot water 6 (at ca. 750C) is directed downwards onto the bottle. This causes heating of the bottle and contents.

As the first point of contact of the bulk of the hot water 6 with the bottle is at the neck 3 and shoulder 4 regions, these regions are rapidly heated and reach the pasteurisation temperature more rapidly than the lower parts of the body 2. This results in thermal stress to the neck region 3 and shoulder region 4, and may cause distortion of the neck 3 and shoulder 4 region. Cold spots or regions may also be formed in the contents of the bottle, particularly in the lower half and near the base 5 of the bottle, e.g. the region generally indicated 7.

Referring to Fig. 2, bottles 1 (generally) of substantially the same shape as those of Fig. 1, i.e. having a body region 2, a neck region 3 and a shoulder region 4 in which the bottle tapers from a wide body section to a narrow neck section, are mounted in holders 8, 9 on a conveyor line 10. One holder 8 holds the bottle 1 about its neck region 3, and the other holder 9 holds the bottle 1 about its body region 2 at a point near to the base 5 of the bottle, by means of suitably shaped cutouts 11, 12. The bottles 1 are closed by closures 13. The bottles 1 are held in an orientation substantially perpendicular to the direction of transport (shown by the arrow A) of the conveyor line 10, i.e. oriented across the conveyor line 10. The bottles 1 rest loosely in the holders 8, 9, and are therefore able to rotate, whilst held in the holders 8, 9, about their neck-base axis. Rotation of the bottles 1 as shown by the arrows B may be achieved during transport of the bottles 1 on the conveyor line 10 by tangential engagement of the body region 2 with a friction pad, a rail or other such means (not shown). The direction of rotation is reversed between the two arrows B.

During their transport along the conveyor line 10 the bottles 1 may also be caused to rock about an axis substantially parallel to the direction of transport, so that the neck region 3 and the base 5 of each bottle rises and falls alternatively as shown by the arrows C in Figs. 2 and 3. This may be achieved by various means (not shown) for example an undulating substrate beneath the conveyor line 10, or undulating or otherwise ramped guides (not shown) which engage with the holders 8, 9 or with the bottles 1 directly. In Fig. 3 the three positions (a), (b) and (c) are progressively sequential along the direction of transport, so that Fig. 3 shows the rocking motion of the bottles 1 about an axis substantially parallel to the direction of transport.

The area shown by Figs. 2 and 3 is part of a heating region. As the bottles 1 are transported on the conveyor line 10, hot water 14 is directed downwards onto the body region 2 of the bottles 1, to raise the contents to a suitable temperature for pasteurising the contents. The hot water 14 (generally) is guided onto the body region 2 of the bottles 1, and kept away from the neck 3, shoulder 4 and base 5 region by means of baffles 15 in the form of shaped metal plates positioned at the sides of the conveyor line 10. By means of these guides the hot water 14 is kept away from the neck 3, shoulder 4 and base 5 regions of the bottle 1, so that they do not experience rapid heating and thermal stress in the way that the bottle 1 of Fig. 1 does.

Therefore in the process illustrated in Figs. 2 and 3 the temperature of the bottle 1 increases most rapidly in its body region 2 rather than in its neck 3 and shoulder region 4 and/or base region 5 of the bottle, and the bottle 2 experiences its maximum temperature in its body region 2 rather than at its neck 3 or shoulder 4 and base region 5.

The heating fluid 14 is being directed into contact with the bottles 1 in such a way that the bulk of the heating fluid 14 first contacts the body region 2 of the bottle 1 rather than the neck 3 and shoulder 4 and base region 5 of the bottle 1.

Contents 16 of the bottles 1 is thereby heated and pasteurised.

The conveyor line 10 may lead from a loading area (not shown) upstream of the heating region shown in Fig. 2, from which the bottles 1 are fed into the heating region. Similarly the conveyor line 10 may lead out of the heating region into a downstream cooling region (not shown) in which the bottles 1 and their contents are cooled, either by exposure to ambient air or by the use of a stream of cooling fluid.

The construction and operation of the conveyor line 10 and the means for directing the hot water 14 onto the bottle 1 may be entirely conventional, as understood in the art.

Claims

Claims:

1. A process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region, characterised in that the containers are transported on a conveyor line in an orientation which is substantially horizontal, through a heating region in which the containers are subjected to a stream of heating fluid, such that the temperature of the container increases most rapidly in its body region rather than in its neck region and/or base region.

2. A process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region, characterised in that the containers are transported on a conveyor line in an orientation which is substantially horizontal, through a heating region in which the containers are subjected to a stream of heating fluid, in a manner such that the container experiences its maximum temperature in its body region rather than at its neck and/or base region.

3. A process for heat treating containers which have an upper neck region defining a mouth opening and a lower body region characterised in that the containers are transported on a conveyor line in an orientation which is substantially horizontal, through a heating region in which the containers are subjected to a stream of heating fluid, the heating fluid being directed into contact with the containers in such a way that the bulk of the heating fluid first contacts the body region of the container rather than the neck and/or the base region of the container.

4. A process according to any one of claims 1 to 3 characterised in that the containers are bottles which have an upper neck region defining a mouth opening and a shoulder region in which the sectional shape of the container tapers from a lower wider body region toward the narrower neck region.

5. A process according to claim 4 characterised in that the bottles are made of moulded PET.

6. A process according to any one of the preceding claims characterised in that the containers are caused to rock as they travel on the conveyor line through the heating region, so that the neck and base pivot about a point intermediate in the height of the container between the neck and base as they travel on the conveyor line through the heating region.

7. A process according to any one of the preceding claims characterised in that the containers are caused to rotate about their neck-base axis as they travel on the conveyor line through the heating region.

8. A process according to any one of the preceding claims characterised in that after passing through the heating region the conveyor line carries the containers into a cooling region where they are allowed to cool to ambient temperature, if necessary aided by contacting the containers with a cooling fluid.

9. A process according to claim 16 characterised in that the entire transport of the containers on the conveyer line through the heating and cooling regions takes place with the containers in the same orientation and on the same conveyor line.

10. Apparatus for heat treating containers which have an upper neck region defining a mouth opening and a lower wider body region, characterised by a conveyor line on which the containers are transported in an orientation which is substantially horizontal; a heating region through which the containers are transported by the conveyor line and in which the containers are subjected to a stream of heating fluid; the manner of subjection of the containers to the heating fluid in the heating region being such that the temperature of the container increases most rapidly in its body region rather than in its neck and/or base region.

11. Apparatus for heat treating containers which have an upper neck region defining a mouth opening and a lower wider body region, characterised by a conveyor line on which the containers are transported in an orientation which is substantially horizontal; a heating region through which the containers are transported by the conveyor line and in which the containers are subjected to a stream of heating fluid; the manner of subjection of the containers to the heating fluid in the heating region being such that the container experiences its maximum temperature in its body region rather than at its neck and/or base region.

12. Apparatus for heat treating containers which have an upper neck region defining a mouth opening and a lower wider body region, characterised by a conveyor line on which the containers are transported in an orientation which is substantially horizontal; a heating region through which the containers are transported by the conveyor line; and means to subject the containers to a stream of heating fluid in the heating region, in which the heating fluid is directed into contact with the containers in such a way that the bulk of the heating fluid first contacts the body region of the container rather than the neck and/or the base region of the container.

13. Apparatus according to claim 10, 11 or 12 characterised in that the conveyor line is constructed such that the containers are conveyed through the heating zone with their neck-base axis substantially perpendicular to the direction of motion of the conveyor line.

14. Apparatus according to any one of claims 10 to 13 characterised in that the conveyor line includes baffles and other guides to direct the heating fluid toward the body of the container, and away from the neck, and shoulder, and/or base region of the container.

15. Apparatus according to claim 14, characterised by baffles in the form of partitions separating the general region of the body from the neck, and shoulder, and/or the base of the container.

16. Apparatus according to claim 15 characterised by baffles and/or guides which comprise partitions aligned parallel to the length of the conveyor line.

17. Apparatus according to any one of claims 10 to 16 characterised in that the containers are caused to rock as they travel on the conveyor line through the heating region, so that the neck and base pivot about a point intermediate in the height of the container between the neck and base as they travel on the conveyor line through the heating region.

18. Apparatus according to any one of claims 10 to 17 characterised in that the containers are caused to rotate about their neck-base axis as they travel on the conveyor line through the heating region.

19. Apparatus according to any one of claims 10 to 18 characterised in that after passing through the heating region the conveyor line carries the containers into a cooling region where they are allowed to cool to ambient temperature, if necessary aided by contacting the containers with a cooling fluid.

20. Apparatus according to claim 19 characterised in that the entire transport of the containers on the conveyer line through the heating and cooling regions takes place with the containers in the same orientation and on the same conveyor line.