FOOD PACKAGING PROCESS AND APPARATUS

Abstract: Packaging apparatus and method combines a removable chamber (10) with a gas snorkel (13) and bag sealing means (19) within the chamber for use in vacuum packaging or controlled atmosphere packaging of foodstuffs. Toggle clamps (18) are provided to grip extremities of the bag (16) and pull it taut during heat sealing. The chamber (10) can be evacuated by means of a separate gas passageway (14) whilst the bag can be evacuated by means of a gas passageway (25) communicating with the snorkel (13) to substantially remove all of the original gas from within the bag or pouch, and prior to heat sealing the bag or pouch the external clamping means (18) can be used to pull the bag (16) or pouch taut to substantially remove wrinkles along the heat sealing zone.

Description: I e : FOOD PACKAGING PROCESS AND APPARATUS FIELD This invention relates to a food packaging process and apparatus for heat sealing food within a package. It has particular, although not sole, application to a process and/or apparatus suitable for packaging foodstuffs such as pork and other meats within a flexible bag or pouch formed from a substantially gas impermeable material or materials. BACKGROUND Previous methods of packaging spoilablc material such as foodstuffs have involved packing the product within a flexible plastics bag or pouch, evacuating the bag or pouch by means of a snorkel whilst at the same time the outside of the bag is exposed to atmospheric pressure, then injecting gas or a gas mixture into the bag, and finally heat sealing the bag to retain the gas or gas mixture. A particular problem found with vacuum packing systems where the bag is exposed to atmospheric pressure, is that the moment that vacuum is drawn on the bag, whilst the neck of the bag is clamped about the "snorkel" or other connecting passageway, the bag rapidly collapses under the pressure differential between the atmosphere on the outside of the bag and the partial pressure within the bag. Pockets of air are often trapped within the bag and cannot be evacuated by the passageway, as the bag collapses between the pocket of air and the end of the passageway. Thus if a gas is injected into the bag prior to heat sealing, it will be mixed with a proportion of air remaining within the bag. This is undesirable, as the remaining air can expose the product, eg meat, to oxidation resulting in discolouring, and spoilage. This problem can be avoided to some extent by providing a snorkel which projects far enough into the bag to contact the product inside, such that the bag can not collapse between the mouth of the snorkel and the product. However, this does not prevent air entrapment at the far comers of the bag or between the bag and the product Furthermore, the use of a long snorkel projecting this far into the bag makes heat sealing of the bag more complicated and time consuming. Attempts have been made to stretch the bag prior to heat sealing by the use of fingers or other components inserted into the edges of the bag, and stretching it outwardly in order to pull it taut prior to heat sealing. These attempts have not proved to be entirely satisfactory, as the fingers interfere with the temporary clamping of the bag and wrinkling of the bag can occur inwardly of the fingers, thus disrupting the eventual heat seal. SUMMARY OF INVENTION It is an object of this invention to provide an improved food packaging process and/or apparatus for packaging food, or one which will at least provide the food industry with a useful choice. In one aspect, the invention provides a food packaging process, in which a product is inserted within a flexible bag or pouch formed from a barrier material or materials, the bag or pouch is placed over a snorkel, and the bag or pouch is clamped shut by way of a mechanical seal about the snorkel, and then the bag or pouch is contained within a chamber, so that both the bag or pouch and chamber can be evacuated substantially simultaneously to prevent premature collapsing of the bag or pouch, whilst substantially all of the air or other gas within the bag or pouch is removed, increasing pressure within the chamber to atmospheric pressure; CHARACTERISED IN THAT prior to heat sealing of the bag inwardly of the mechanical seal, the bag is externally clamped at or adjacent each edge by a respective pair of clamping devices which gently pull the bag taut to substantially remove wrinkles prior to heat sealing of the bag adjacent said pairs of clamping devices . Preferably the bag or pouch4s formed from a substantially gas impermeable laminate, and the preferred laminate material is one formed of polyester-aluminium foil- polyethylene laminate of immeasurably low oxygen permeability. However, other materials can be used, depending upon the shelf life of the intended product. For example in some applications, a laminate of ethylene vinyl acetate copolymer- polyvinylidene chloride (PVDC) laminate can also be used. Any other barrier material capable of being heat sealed to form an enclosed package can be used, although the above two laminates are preferred for use in food grade packaging. It is particularly preferred that the bag or pouch is heat sealed from both above and below in order to provide sufficient heat to heat seal the entire laminate. In which case, it is preferred that one of the heating elements is substantially flat whilst the other heating element is substantially convex in order to provide sufficient pressure against the laminate. Each heating element is preferably covered with a release material such as fibreglass, in order to prevent the laminate from bonding to the heat sealing element. It is particularly preferred that the process of this invention is used to package meat, especially pork, chicken, lamb and beef within a substantially oxygen free, carbon dioxide atmosphere, as we have found that the use of the process of this invention enables meat to be shipped in a chilled state within a carbon dioxide atmosphere heat sealed within a pouch, enabling shelf life of up to 12 weeks for pork and other meats. All prior art techniques to our knowledge have not been able to provide such a shelf life for pork and other meats unless the product has been deep frozen. There is little demand for deep frozen meat, whilst there is a substantial demand for chilled meat By providing a process which enables meat such as pork to be packaged within a carbon dioxide atmosphere and shipped in a chilled state with a shelf life of up to 12 weeks, it is now possible to ship such meat by sea freight from Europe or North America to Japan or other markets which were not hitherto accessible by means of sea freight because of the long transit times relative to the short shelf life of the prior art packages. In another aspect, the invention provides apparatus for use in packaging food and the like, including: a chamber, means for holding within said chamber a flexible bag or pouch containing the food or the like; a heat sealing zone within said chamber, a first gas passageway providing communication between the interior of the bag or pouch and a first valve means, a second gas passageway providing communication between that portion of the interior of the chamber which surrounds said bag or pouch and a second valve means, means for closing said chamber, first pressure sensing means for sensing the gas pressure within the bag or pouch, second pressure sensing means for sensing the gas pressure within said chamber about said bag or pouch; CHARACTERISED IN THAT there is means for clamping said bag or pouch about said first gas passageway to isolate the food or the like and any original gas contained in the bag or pouch from gas contained in said chamber about said bag or pouch, and means for heat sealing the bag or pouch apart from the clamping means, and external clamping means on either side of the bag adjacent said heat sealing zone; whereby in use the chamber can be evacuated by means of the second gas passageway whilst the bag or pouch can be evacuated by means of the first gas passageway to substantially remove all of the original gas from within the bag or pouch, and prior to heat sealing the bag or pouch the external clamping means can be used to pull the bag or pouch taut to substantially remove wrinkles along the heat sealing zone. Preferably the first pressure sensing means for sensing the gas pressure within the bag or pouch includes a sensor which protrudes slightly from the end of the first gas passageway so as to sense the premature collapsing of the bag about the end of the sensor and/or the first gas passageway. It is particularly preferred that the first gas passageway is in the form of a snorkel which can be inserted into the open end of the bag or pouch, and that the first pressure sensing means includes a sensing tube or the like protruding slightly from the end of the snorkel. It is particularly preferred that the snorkel is capable of being moved up or down relative to the chamber so that the means for closing off the bag or pouch can take the form of a mechanical clamp which squeezes the bag about the snorkel in order to provide a substantially gas tight closure of the bag about the snorkel separate from the subsequent heat sealing of the bag. It is a particular feature of this invention that the mechanical clamping or heat sealing of the bag about the snorkel takes place towards the mouth of the bag whilst fhe subsequent heat sealing of the bag takes place along a line which is adjacent to but separate from the line of mechanical clamping pressure about the snorkel. This enables the bag to be heat sealed prior to removal of the snorkel. DRAWINGS These and other aspects of this invention, which should be considered in all its novel aspects, will become apparent from the following description, which is given by way of example only, with reference to the accompanying drawings, in which: Figure 1: illustrates the snorkel, and the first pressure sensing means in top plan view with the upper clamping bar removed. Figure 2 : illustrates a front elevation of the snorkel and the placement of fhe two pairs of bag stretching means. Figure 3: illustrates the internal arrangement of one of the lower bag stretching means. Figure 4: illustrates the relative cross sections of the upper and lower heating elements. Figure 5: illustrates a schematic view of the preferred packaging apparatus, but omitting details of the bag stretching means. Schematic View - Figure 5 This apparatus includes a chamber 10 defined by a removable cover 11 and a base 12. Gas passages are provided, connecting the apparatus to a vacuum source 23 and one or more gas sources 24. One passage 25 includes a snorkel 13 (described in more detail below with reference to figures 1 and 2). the snorkel is intended for connection with a container held in the chamber 10, as detailed below, and a second passage 14 provides access to the chamber 10 itself. In some applications, it may be desirable to provide pairs of passageways, one connected to the vacuum source and one to a gas source. Alternatively, as shown single passageways may be used with appropriate valves to switch the passageway between the two functions. Preferably the chamber 10 is of a size able to comfortably accommodate a box 15 and heat sealable bag 16 with its contents 17. Temporary mechanical clamping and heat separate heat sealing In its preferred form the apparatus includes clamping and heat sealing apparatus for the bag 16, inside the chamber 10, separate and independently movable from the cover 11. This apparatus includes clamping bars 18 mounted around the snorkel 13 for temporarily clamping the mouth of the bag around the snorkel 13, and heat sealing bars 19 positioned beyond the snorkel 13 for heat sealing the mouth of bag 16 between the snorkel and the product 17. The clamping bars 18 are preferably flat are surfaced with resilient material so that they can be squeezed tightly about the bag and snorkel to provide a good seal. The upper heat sealing bar 19 is preferably flat whilst the lower heat sealing bar is preferably convex as shown in figure 4. One or both heat sealing bars 19 are movable, preferably by the use of a pneumatic cylinder 20, such that the mouth of the bag can be left open or sealed shut between the snorkel 13 and the product 17. The upper clamping bar 18 and heat sealing bar 19 can be mounted on a pivotable jaw 21 with a handle 22 by which it may be moved up or down. All this apparatus is contained in the chamber 10 along with the product 17 and its packaging, and is covered by the lid 11. An airtight seal is formed between the lid 11 and the base 12 in normal use. It is preferable for the clamping bars 18 to be positioned behind the sealing bars 19 as shown, rather than in front of them. If the clamping bars 18 were positioned in front of fhe sealing bars 19 with the snorkel 13 protruding through them, it would be necessary to withdraw the snorkel before sealing the bag, and furthermore a small pocket of air would inevitably be trapped between the clamping bars and the seal, and would be released into the bag upon removal of the clamping bars. With the arrangement of the present invention the snorkel is not required to move, and there is no air entrapment at the mouth of the bag. In use, the product 17 to be packed is placed within a heat sealable bag 16 and box 15, and is then placed within the chamber 10. The chamber has appropriate seals about its edge, so that the chamber itself can be evacuated as well as the bag. The bag is placed within the chamber 10 and the mouth of the bag 16 fitted over the snorkel 13. The bag is then clamped off across the snorkel with the pair of clamp bars 18. The chamber 10 and the bag 16 are evacuated, preferably simultaneously, so that the bag is completely emptied. By controlling the pressure within the chamber as the bag is evacuated, the bag can be controlled so that it does not collapse too soon, cutting off communication between contents and the snorkel 13. Preferably both the chamber and the bag are evacuated from the same source, but the snorkel 13 is narrower than the passageway 14. This means that the chamber is evacuated faster than the bag, and the bag expands inside the chamber as it is emptied, rather than collapsing. This prevents air being trapped in pockets in the bag. Alternatively, the bag and the chamber could be evacuated at the same rate. Even if the bag empties slightly faster than the chamber and collapses as a result, the difference between the air pressure in the bag and the air pressure around it will not be great enough to trap air inside. When a desired vacuum level in the chamber is achieved, a vacuum pressure switch 26 stops the evacuation and holds the chamber at that vacuum level. The evacuation of the bag continues through the nozzle 13, and the bag collapses as a result. When the desired vacuum level in the bag is reached a second pressure sensor 27 activates the appropriate valves. The chamber and the bag are then reinflated. Any suitable pressure sensor can be used, although we prefer to use pirani gauges as they are suitable for measuring pressures of the order of 15mm to 10 " ^ mm of mercury. By using the same vacuum source to evacuate both chamber and bag it is easy to avoid having any great difference between the pressures in each. To speed up the last stages of evacuation of the bag, it may be found desirable to refill the chamber slightly after activation of the valves by the first pressure sensor and initial collapse of the bag, to put greater pressure on the bag and squeeze the last of the air out Such collapsing of the bag could result in entrapment of air, but because the bag is already substantially evacuated at this stage this will in general not be a problem. Snorkel The snorkel 13 is best seen from figures 1 and 2. It is preferably free floating so that it can move relative to the clamping bars so that the bag can be securely clamped about the snorkel. In general the width of the snorkel will be substantially less than the width of the bag (about half the bag width) and is preferably substantially elongate with tapered ends when seen in front elevation. It communicates with a manifold 30 which is connected to the vacuum source. Preferably a pressure sensor 27 protrudes slightly from the front of fhe snorkel and takes the form of a tube 31 passing through the snorkel and connected to a an appropriate pressure measuring device 27 A. An appropriate controller such as a microprocessor can be used to monitor the pressures and time taken for both the bag and chamber to be evacuated to their lower pressure limits. For example the passage 14 may be designed to allow the chamber to be evacuated within say 20 seconds whilst the bag may be expected to be evacuated within 25 seconds. If the bag fails to reach its expected low pressure limit within say 30 seconds of start (as monitored at 27 A) then the cycle can be aborted as it is likely that the bag may have partly collapsed about the end of tube 31 thereby preventing the bag from being fully evacuated (and preventing the tube 31 from reaching the required lower pressure limit. The system of the present invention also allows visual checking (as a means of secondary quality control), in that most of the bag (except for the portion around the snorkel) can be seen to inflate and collapse within the chamber (given one or more windows in the chamber lid or walls) at different times in the process. If, for example, the proper vacuum is not achieved in the bag for any reason, it will not collapse even if a partial reduction of pressure has occurred, because the internal pressure will still be greater than that in the chamber. When the bag is fully empty, or as empty as the vacuum pump can make it within the desired cycle time, the chamber and the bag are reinflated, preferably at the same rate. This time the bag is filled with a selected gas or gas mixture introduced through the nozzle 13. In the case of packaging meat the gas is commonly Carbon Dioxide, although other gases or gas mixtures may be used. Depending upon the nature of the contents of the bag other gas mixtures may be used to control fhe storage, ripening, or other qualities of the item stored within the bag. ' Whilst the bag is being filled with a gas or gas mixture, the chamber is also filled, most conveniently with air, although other gases could be used. By filling the chamber at a controlled rate at the same time as filling the bag, it is possible to balance the pressure between the gas within the bag, and the air within the chamber. This allows the bag to be filled accurately with a metered quantity of gas, and also avoids undue pressure being placed on the bag. Bag Stretching Means When atmospheric pressure has been reached in the chamber, the cover 11 of the chamber can be removed, the bag stretching means can be brought into operation just prior to heat sealing. The bag stretching means preferably comprises two pairs of clamps 40 capable of gripping the outside edges of the bag adjacent the heat sealing zone. An upper clamp block 41 is mounted on the front of the upper heat sealing bar mounting and is slidable along a pair of horizontal rods 43 being spring biased into a resting position. A lower block 42 is movable upwardly about a parallel linkage as shown in Figure 3, the linkage being attached to the front of the lower heat sealing bar mounting. A stop limits the unrestrained rotation of the linkage by a torsion spring 51 which biases the linkage upwardly with respect to the lower heat sealing bar mounting. Each clamp block preferably has a resilient surface to grip the bag. Preferably the upper sealing bar is fixed in position and the lower sealing bar and its associated clamp blocks moves upwardly towards the bag. As the lower blocks 42 grip the bag they and the upper blocks are caused to move horizontally outwardly to pull the bag taut. Preferably the lower blocks 42 have an internal shuttle 46 connected to the outer block by a spring 47 which prevents the blocks from over-stretching the bag. The relative clamp and spring sizes can be adjusted to suit different bag materials and thicknesses. Whilst the bag is held taut and substantially wrinkle free about the heat sealing zone the heat sealing bars 19 are brought together to seal the bag 16. If two chambers are used together, the cover 11 can be shifted to the second chamber at this stage, and evacuation of another bag commenced while the first is being sealed. When the bag is sealed, the clamping bars 18 can be released and the bag removed from the chamber. ADVANTAGES The invention is equally applicable to vacuum packaging an to controlled atmosphere packaging. It has the advantage that when used for controlled atmosphere packaging the bag can be well evacuated to leave a very low amount of residual air, and then accurately filled with a known quantity of gas. This avoids the disadvantages of prior vacuum packaging methods in which the bag is exposed to atmospheric pressure during the vacuum and gas flushing operations. The invention also has the advantage that only the bag is filled with the required amount of gas, and no gas is allowed to escape into the chamber. It is also believed that the bags are less likely to be damaged in the operation as there can be little or no stress on the bag during filling and stretching of the bag to remove wrinkles need only take place just prior to heat sealing. This is particularly advantageous in the case of filling fhe bags with a gas such as carbon dioxide as the bags are gently stretched whilst at atmospheric pressure (and the stretching does not interfere with the evacuation or filling steps). Finally, it will be appreciated that various alterations or modifications maybe made to the foregoing without departing from the scope of this invention as set forth in the following claims.

Claims: CLAIMS 1. Apparatus for use in packaging food and the like, including: a chamber, means for holding within said chamber a flexible bag or pouch containing the food or the like; a heat sealing zone within said chamber, a first gas passageway providing communication between the interior of the bag or pouch and a first valve means, a second gas passageway providing communication between that portion of the interior of the chamber which surrounds said bag or pouch and a second valve means, means for closing said chamber; first pressure sensing means for sensing the gas pressure within the bag or pouch, second pressure sensing means for sensing fhe gas pressure within said chamber about said bag or pouch; CHARACTERISED IN THAT there is means for clamping said bag or pouch about said first gas passageway to isolate the food or the like and any original gas contained in the bag or pouch from gas contained in said chamber about said bag or pouch, and means for heat sealing the bag or pouch apart from the clamping means, and external clamping means on either side of the bag adjacent said heat sealing zone; whereby in use the chamber can be evacuated by means of the second gas passageway whilst the bag or pouch can be evacuated by means of the first gas passageway to substantially remove all of the original gas from within the bag or pouch, and prior to heat sealing the bag or pouch the external clamping means can be used to pull the bag or pouch taut to substantially remove wrinkles along the heat sealing zone. 2. Apparatus for use in packaging food and the like, as claimed in the preceding claim and CHARACTERISED IN THAT said first valve means is switchable between a vacuum source for the controlled removal of gas from the bag and a gas source for the introduction of gas into the bag. 3. Apparatus for use in packaging food and the like, as claimed in the preceding claim and CHARACTERISED IN THAT said first pressure sensing means for sensing the gas pressure within the bag or pouch includes a sensor which protrudes slightly from the end of the first gas passageway so as to sense the premature collapsing of the bag about the end of the sensor and/or the first gas passageway. 4. Apparatus for use in packaging food and the like, as claimed in the preceding claim and CHARACTERISED IN THAT said first gas passageway is in the form of a snorkel which can be inserted into the open end of the bag or pouch, and that the first pressure sensing means includes a sensing tube or the like protruding slightly from the 5 end of the snorkel. 5. Apparatus for use in packaging food and the like, as claimed in the preceding claim and CHARACTERISED IN THAT said snorkel is capable of being moved up or down relative to the chamber so that the means for closing off the bag or pouch can take 10 the form of a mechanical clamp which squeezes the bag about the snorkel in order to provide a substantially gas tight closure of the bag about the snorkel separate from the subsequent heat sealing of the bag. 6. Apparatus for use in packaging food and the like, as claimed in the preceding 15 claim and CHARACTERISED IN THAT said mechanical clamping or heat sealing of fhe bag about the snorkel takes place towards the mouth of the bag whilst the subsequent heat sealing of the bag takes place along a line which is adjacent to but separate from the line of mechanical clamping pressure about the snorkel. 20 7. A packaging process, in which a product is inserted within a flexible bag or pouch formed from a barrier material or materials, the bag or pouch is placed over a snorkel, and the bag or pouch is clamped shut by way of a mechanical seal about the snorkel, and then the bag or pouch is contained within a chamber, so that both the bag or pouch and chamber can be evacuated substantially simultaneously to prevent premature 25 collapsing of the bag or pouch, whilst substantially all of the air or other gas within the bag or pouch is removed, increasing pressure within the chamber to atmospheric pressure; CHARACTERISED IN THAT prior to heat sealing of the bag inwardly of the mechanical seal, the bag is externally clamped at or adjacent each edge by a respective 30 pair of clamping devices which gently pull the bag taut to substantially remove wrinkles prior to heat sealing of the bag adjacent said pairs of clamping devices. 8. A food packaging process as claimed in the preceding claim CHARACTERISED & IN THAT the bag or pouch is formed from a substantially gas impermeable laminate, 35 AND is heat sealed from both above and below. 9. A food packaging process as claimed in the preceding claim wherein the product is a foodstuff such as pork, chicken, beef, lamb or the like and CHARACTERISED IN THAT when the bag or pouch and chamber have been evacuated the bag or pouch is filled with selected gas or gases, to substantially atmospheric pressure whilst at the same time the chamber is returned to atmospheric pressure.

Inventors: COSTELLO ANTHONY WILLIAM, PERYER BRYAN MILTON, COSTELLO, ANTHONY, WILLIAM, PERYER, BRYAN, MILTON
Applicants: PIPER JAMES WILLIAM, PIPER, JAMES, WILLIAM
Application year: 1989
Main classification: B65B31
IPC codes: B65B31