WO2000044234A1

WO2000044234A1 - Shirred collagen casing stick having an end closure and method and apparatus for making same

Info

Publication number: WO2000044234A1
Application number: PCT/GB2000/000133
Authority: WO
Inventors: Alexander Forrest; Robert Nichol Mackellar David
Original assignee: Devro-Teepak Limited
Priority date: 1999-01-29
Filing date: 2000-01-20
Publication date: 2000-08-03
Also published as: AU3063400A; GB9902076D0

Abstract

A shirred casing stick (10) with an improved end closure which can be used with high speed sausage filling machines is described. The end closure is formed with a relatively smooth finished edge (20) such that when the meat emulsion is projected into the collagen casing stick, the filled leading end continues on its desired trajectory for subsequent processing through voiders and a belt transport system of the high speed filling machine. In a preferred arrangement this is achieved by simultaneously pressurising and heating the leading end of the collagen casing and then trimming the excess casing from the heat treated end to create a smooth edge (20) perpendicular to the longitudinal axis of the casing stick. The end closure is then re-inserted into the casing stick which can then be, in turn, loaded into the high speed filling machines for filling by meat emulsion in the usual way. Embodiments of the invention are described.

Description

SHIRRED COLLAGEN CASING STICK HAVING AN END CLOSURE AND METHOD AND APPARATUS FOR MAKING SAMF1

The present invention relates to edible food casings and especially to shirred tubular food casings of edible materials having an end closure. The present invention also relates to apparatus for, and a method of, making such end closures in shirred collagen casing sticks.

Shirred collagen casing sticks with end closures are well known in the art and a typical example is disclosed in U.S. Patent No. 3,965,537. The current Devro automatic end seal unit (AESU) applies an end closure or end seal to a stick of collagen casing by twisting a short length of the collagen casing between two V-shaped jaws. The type of end closure was developed specifically to address the requirements of Handtmann - PAL 51 and 52 series of automatic sausage filling machines. However, the closure type is applicable to a number of other automated filling machines which operate on the same principle .

In order to create the end closure in the shirred casing, jaws of the automatic end seal unit are heated to a pre-set temperature and clamping pressure applied to the jaws, and thus to the casing, in two stages; low pressure during the initial twisting and high pressure during the final part of the cycle.

The combination of mechanical pressure, heat and friction produces a welding and smearing action to the collagen trapped within the jaws resulting in a "weld" type closure with some of the collagen becoming gelatinised in the region of the weld. A prior art twisted end closure is shown in Fig. 1 of the drawings with a leading end 8 formed from rolled up and gelatinised collagen casing and twisted casing portions 9.

The final part of the end closure manufacturing process uses a blade to trim the excess casing from the welded end and an inserter to position the closed end back inside the bore of the casing stick. The twisting action also provides an additional feature to the closure by providing it with the ability to absorb the initial surge of kinetic energy of the meat emulsion as the closure unwinds during the start of the filling process. Without this initial absorption of kinetic energy, the mechanical strength of the closure may, in some instances, be insufficient to contain this initial pressure surge. During the filling of the first sausage, as this part or "buffer" of twisted collagen casing unwinds, it imparts a spinning motion to the first sausage which is produced. On the PAL 51 and 52 series of machines, the moving belt system which transports the filled sausage through the machine is situated close to the "chuck", that is, the point at which the filled sausage is formed and, as such, the spinning action of the first sausage is contained and is consequently insignificant. The meat pumping system on the PAL 51 and 52 types of machine uses a pulsing type pump to provide the portioning action by creating slugs of sausage meat emulsion in combination with the momentary rotation of the chuck.

The traditional end closure when used with PAL 51 and 52 series of machines works well and the seal strength is sufficient to retain filled sausage meat with the aforementioned type of meat pumping system.

However, recently, a new generation of automated filling machines has been produced by Handtmann and which are known as the AL series. The actual filling speed of these machines is in the region of 1200 to 1500 links per minute compared to 500 to 700 links per minute for the PAL 51 and 52 series. Furthermore, the meat pumping system in the new generation of machines is different : the meat is continuously pumped and, therefore, avoids slugs of meat emulsion. This means that portioning

"voiders" are necessary to nip the filled rope of sausage emulsion to create links and the belt transport system is also different. These elements provide the opportunity for the first filled sausage to rotate and deviate from the intended trajectory and thus miss entry to the voiders and to the belt transport system. Because the meat pumping system is continuous at high speed, this can result in filled casing being inadvertently distributed over the factory floor before the machine is stopped. The first filled sausage is caused to rotate because of the initial twisting which is applied during manufacture of the end closure. With such high speed machines, although some end closures may follow the desired trajectory for subsequent uptake by the belt transport system, there are too many instances of missed entry which causes the aforementioned problems. This means that the area must be cleaned and the system re-set and tried again. The alternative is to run the new generation machines at a much slower speed equivalent to the speed of the PAL 51 and 52 machines which still may not solve the problem. An object of the present invention is to provide a shirred casing stick with an improved end closure which can be used with high speed sausage filling machines to obviate or mitigate at least one of the aforementioned disadvantages . This is achieved in its broadest sense by providing a shirred collagen casing stick without a twisted leading end. Instead, the end closure is formed with a relatively smooth finished edge such that when the meat emulsion is projected into the collagen casing stick, the filled leading end continues on its desired trajectory for subsequent processing through the voiders and the belt transport system of the high speed filling machine.

In a preferred arrangement this is achieved by simultaneously pressurising and heating the leading end of the collagen casing and then trimming the excess casing from the heat treated end to create the smooth edge. Most desirably, this smooth edge is perpendicular to the longitudinal axis of the casing stick. The end closure is then re-inserted into the casing stick which can then be, in turn, loaded into the high speed filling machines for filling by meat emulsion in the usual way. According to a first aspect of the present invention there is provided a shirred casing stick having an untwisted leading end with an end closure of sufficient length to retain meat emulsion injected into the casing, the leading end terminating in a substantially smooth edge transverse to the longitudinal axis of the shirred casing stick.

Preferably, the smooth edge is substantially perpendicular to the longitudinal axis of the shirred casing stick. Conveniently, the shirred casing stick end closure is created by applying heat and pressure over a portion of the casing length to form a flattened gelatinised portion with excess casing distal to the flattened portion being removed, and then allowing the gelatinised portion to cool and solidify to leave the end closure. The end closure is then re-inserted into the shirred casing stick for subsequent use in the high speed filling machine.

Conveniently, a transition portion is provided between the heat sealed end closure portion and the shirred casing, the transition portion being partly heat sealed which is sufficient to receive the impact of meat emulsion as the casing is filled such as to buffer the force of the emulsion during filling and thus minimise the impact of the meat emulsion on the end closure. Preferably also, the end closure portion is about 20 mrrts in length and the transition portion is about 10 mms in length, irrespective of the diameter of the shirred casing. The shirred casing generally varies in diameter between 13 and 30 mms. According to another aspect of the present invention there is provided a shirred collagen casing stick having an end closure at a leading end thereof for retaining meat emulsion injected into said shirred casing, said end closure having a first heat seal portion with a substantially smooth leading edge and a second heat seal portion disposed between said first heat seal portion and said shirred casing, said second heat seal portion being adapted to separate in response to the force of said injected meat emulsion for buffering the force on said end closure.

According to another aspect of the present invention there is provided a method of manufacturing an end closure on the leading end of a stick of shirred collagen casing, said method comprising the steps: extending the leading end of said shirred casing to form an extended portion, flattening an extended portion over a pre-determined length of the extended portion, heating the flattened length to gelatinise the flattened point and then allowing the gelatinised portion to cool and solidify to create an end closure portion and to create a transition portion between the end closure portion and the stick of shirred casing, and cutting the flattened casing at the distal end of the end closure portion to remove excess casing and to provide a smooth edge to said end closure portion. Preferably, the method of manufacturing said end closure includes applying heat and pressure to gelatinise said casing over the length of said flattened portion.

Preferably also, said method includes applying heat and pressure to said flattened portion for a pre- determined time to ensure that all of the flattened portion is substantially gelatinised prior to cooling. Conveniently, the heat and pressure creates partial gelatinising of the casing between the treated portion and the shirred casing thereby forming the transition portion. The transition portion acts as a buffer to reduce the force of impact on the end closure as the leading end of the casing is filled with meat emulsion by the meat pump .

Once the end closure has been manufactured it is then re-inserted into the shirred collagen casing stick for subsequent use in the high speed sausage filling machine .

According to yet another aspect of the present invention there is provided apparatus for creating an end closure on shirred collagen casing stick, said apparatus comprising, inserting means for coupling to the leading end of a shirred collagen casing stick, said inserting means being moveable from a first position to engage with said leading end of the collagen casing stick to a second position wherein said leading end of said collagen casing stick is extended for subsequent treatment by said apparatus , casing clamp means for clamping said extended collagen casing leading end in position, heating and cutting means for flattening said clamped casing and for heating the clamped casing to a pre-determined temperature to heat seal said flattened collagen casing into an end closure and for cutting said casing to provide a substantially smooth cut edge on said leading end when said casing is in said clamped third position, said insertion means being moveable to said first position to re-insert said completed end seal into said shirred collagen casing stick.

Preferably, said apparatus includes removing means for removing the cut portion of said casing held by said clamp means. Conveniently, said removing means includes clamp actuation means coupled to said casing clamp means for moving said clamped casing to a third position where excess casing is torn from said cut portion for subsequent removal.

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Fig. 3b is a similar view to Fig. 2a, showing the apparatus in the gripping position for gripping the leading end of the shirred collagen casing stick;

Fig. 3c shows the apparatus in the pulling position where the shirred casing has been pulled into the apparatus for subsequent treatment;

Fig. 3d shows the apparatus in accordance with the embodiment of the invention in the heat crimping and cutting position; Fig. 3e shows the apparatus in the tear-off position

(to a slightly larger scale) in which the free distal end of the shirred collagen casing is removed to leave an end closure with a smooth edge;

Fig. 3f shows the apparatus after the seal has been made in which the end closure has been re-inserted into the shirred collagen casing stick;

Fig. 4 is a longitudinal sectional view taken on the lines 4-4 of Fig. 3e depicting the heat sealed and transition portions of the end closure and showing the tear-off portion distal to the gelatinised portion for subsequent removal ;

Fig. 5 is a side view of the apparatus shown in Figs. 3a-3f;

Fig. 6 is a sectional view taken on 6-6 of Fig. 5 and showing the cutting blade for cutting the casing clamped in Fig. 5, and

Fig. 7 is a diagrammatic side view of the leading end of a stick of shirred casing manufactured in accordance with an embodiment of the present invention filled with meat emulsion and being projected through part of the filled casing transport system of a high speed sausage filling machine.

Reference is first made to Fig. 2 of the drawings which depicts part of a shirred collagen casing stick, generally indicated by reference numeral 10, which has a leading end 12 at which is disposed an end closure 14 which consists of two parts; a heat sealed planar portion 16 consisting of portions 16a, 16b and a partly heat sealed transition portion 18 which is formed in accordance with the apparatus and method of the invention, as will be later described in detail. The portion 16 terminates in a smooth cut edge 20 which is substantially perpendicular to the longitudinal axis 22 of the shirred collagen casing stick 10. As will also be described, a casing portion 24, known as the 'tail portion', is shown in broken outline distal to the gelatinised portion 16. It is this portion which is removed by cutting and discarded. It will be appreciated that the leading end of the shirred collagen casing stick shown in Fig. 2 does not have any twists imparted to it during manufacture . This means that when the end closure is re-inserted in the collagen casing stick and the collagen casing stick is inserted into a high speed continuous sausage filling machine, the impact and force of the meat filling will a) not burst the sealed closure, and b) force the leading end to move in the direction of the trajectory with minimal deviation so that the filled collagen casing is directed through the sausage transport system.

The apparatus and method which is used to create the end closure 16 and transition seal 18 will now be described in detail with reference to the accompanying drawings .

Reference is first made to Fig. 3a which depicts an end closure manufacturing device, generally indicated by reference numeral 30. The device has parts which are manufactured from stainless steel for ease of cleaning, disinfecting and in the interest of hygiene. The device has a base plate 32 on which is mounted a casing gripping and pulling mechanism, generally indicated by reference numeral 34, which will be later described in detail, and which is adapted to grip the leading end of the stick of shirred casing 10 to pull the leading end into the device 32 for subsequent treatment and then, after treatment, to re-insert the treated leading end with the end closure back into the shirred casing stick 10. The stick of shirred casing is shown in Figs. 3a to 3f, Fig. 4 and Fig. 5 in broken outline for ease of reference. The gripping and pulling mechanism 34 is actuated via a double-acting piston 36 under the control of a programmable logic controller (PLC) (not shown in the interests of clarity) to move an inserter 36 in a reciprocal motion to and away from the shirred casing. The inserter 36 is adapted to grip the leading end of the shirred casing 10 as shown. The position in Fig. 3a is the passive position. The inserter is coupled to a cam 38 which has a cam surface 40 for engaging rollers, generally indicated by reference numeral 43. The cam 38 is, in turn, coupled to mechanism 34 which, in turn, is coupled via a floating coupling 46 to the double-acting piston 36.

A pair of arms 48a, 48b are pivotally mounted in the mechanism 34 and carry clamping jaws 50a and 50b respectively at the free ends respectively. Rollers 43 can move laterally in response to contact with the cam surface 40 so as to displace jaws 50a and 50b inward to a clamping position as shown in Fig. 3b.

At the front of the plate is disposed a pair of heater blocks 52a, 52b which are coupled to the structure 30 via insulating pads 54a, 54b respectively. The heater blocks are adapted to be coupled to a source of electrical energy for providing electrical resistance heating of the blocks to a pre-determined temperature for heat treatment of the shirred casing, as will be later described in detail . Between the front edge of each heater block is disposed an insulating strip 55a, 55b which is triangular in shape in plan view for providing a thermal heating gradient to create a closure transition zone in the end closure to be formed, as will be later described in detail. The heater blocks 52a, 52b have respective opposing faces 57a and 57b in which is disposed a respective insulator strip 59a, 59b about 2mm wide, best seen in Fig. 5 for block 52a and Fig. 4 for block 52b, which separate each heater block into two heater block elements 52al,52a2 and 52bl and 52b2. The heater block elements 52al,52bl are heated to 170°C and the block elements 52a2 and 52b2 are heated to 220°C. Referring back to Fig. 2, the higher temperature of blocks 52a,52b2 results in a stronger bond between the casing surfaces in portion 16a than 16b to ensure that the free end of the casing, when cut, is sufficiently strong to accommodate meat emulsion of lower viscosities which impacts on the end closure with greater force than high viscosity meat emulsion.

A circular aperture, generally indicated by numeral 56 (shown in broken outline) , is disposed in the base plate 32 through which excess shirred casing, tail 24, is sheared off from the formed end closure can be discarded, as will also be later described in detail.

It will be reiterated that the arrangement of the apparatus shown in Fig. 3a is in the passive position in which no treatment has yet been made to the shirred casing. In this position it is shown that the leading end of the shirred casing is coupled to the inserter 36 for subsequent processing. Reference is now made to Fig. 3b which depicts the end closure apparatus in the gripping position. In this case, under the action of the programmable logic controller, the double-acting piston has been actuated to withdraw rod 44 in the direction of arrow A, thus pulling the cam surface 38 in the same direction and forcing the arm rollers 43 to be displaced sideways. This forces arms 48a and 48b to rotate about pivots 42 towards each other such that the jaws 50a and 50b clamped the shirred casing 10 as shown. After the shirred casing 10 has been clamped, the entire assembly 34 is moved in the direction of arrow B by actuating a pneumatic cylinder 66, as best seen in Figs. 4 and 5 of the drawings. This moves the mechanism 34 back via rollers 35 which move along knife-edge HEPCO slide 37 until mechanism 34 reaches end stop 62 which sets the position of jaws 50a, 50b where the shirred casing 10 is to be compressed and heat sealed. In this position it will be best seen from Figs. 3c and 3d that the jaws 50a, 50b overlie aperture 56.

Reference is now made to Fig. 3d of the drawings which depicts the apparatus in the heat crimping and cutting position. In this position heater blocks 52a and 52b are moved inwards to firstly clamp the shirred casing 10 in the position as shown and compress the tubular casing to a planar or flattened format. The heater blocks 52a, 52b are actuated by an air chuck (not shown in the interest of clarity) so that the jaws of the heater blocks, indicated by reference numerals 53a and

53b, always close on the centre line 80, as shown in Fig. 3d. In the position shown in Fig. 3d the blocks 52a and 52b are heated for a pre-determined time under the control of the PLC. This is such that the blocks are heated to a pre-determined temperature which is typically about 165°C. The blocks contain thermocouples (not shown) from which the temperature of the blocks can be monitored. If the temperature monitored is within a pre-determined temperature range, for example +/- 10°C, then the quality of the closure is satisfactory and will be accepted. If the temperature range is greater than +/- 10°C from the desired value, then the quality of the end closure is unsatisfactory and will be discarded automatically after the heat sealing operation is completed. This acceptance or rejection does not form part of the invention but it will be understood that the shirred casing sits in a tray or clamping device, under the control of the PLC. When the operation is complete the PLC decides whether the closure is acceptable or not on the basis of temperature time measurements.

Acceptance results in the shirred casing stick with end closure being tipped to one side and, conversely, rejection results in the casing stick being tipped to a collection bin on the opposite side.

The heating lasts until flattened sides of the tubular casing are gelatinised, i.e. are effectively melted and formed into an essentially homogenous material. After heating, the gelatinised portion cools quickly to solidify and form the end closure 16. However, in the part of the flattened casing opposite the insulators 55a and 55b the temperature is insufficient to cause complete gelatinisation and instead only part of the collagen surfaces are bonded together, thus forming a transition zone 18 over the depth of the insulator, as best seen in Fig. 2 of the drawings. The transition zone 18, because it is incompletely gelatinised tends to separate on receipt of impact or force due to meat emulsion being forced through the casing by the continuous pump and thus acts as a buffer for the end closure, as will be later described in detail.

Reference is now made to Figs. 3e and Fig. 4 and Fig. 6. Fig. 3e depicts the apparatus in the tail removal condition and Fig. 4 is a sectional view taken on the lines 4-4 of Fig. 3e. Fig. 6 shows the cutting blade 64 mounted on heating block 52b. When the blocks 52a, 52b are closed as shown in Fig. 3d the blade 64 perforates the leading end 12 of the casing 10. This tear is sufficient to allow the portion 24 to be removed as shown in Figs. 3e and 4 when mechanism 34 and jaws 50a, 50b are retracted in direction of arrow A. This occurs when pneumatic cylinders 66,68 are actuated together to move the mechanism 34 and jaws 50 to tear-off portion 24 as best seen in Fig. 4, through aperture 56 under the effect of a venturi created vacuum. As best seen in Fig. 4, after the blade 64 cuts through the leading end 12 of the shirred casing, tear-off portion 24 is removed through aperture 56 due to a vacuum created by a venturi-induced airflow beneath the aperture 56. After the tear-off portion 24 has been removed, the end closure 16 and transition seal 18 have been correctly formed and thus the leading end 12 of the shirred casing 10 is able to be inserted back into the casing. This is achieved using the programmable logic controller double-acting piston to force the cam 38 and inserter 36 towards the shirred casing stick 10. At the same time, the heating blocks 52a and 52b are separated and, simultaneously, jaws 48a and 48b are opened to allow the insertion rod and cam to be moved outside the clamping device 30 and re-insert the leading end 12 of the shirred casing back into the tube of casing 10, as best seen in Fig. 3f of the drawings .

Thus, it will be understood that the shirred tubular casing manufactured in accordance with the apparatus and method hereinbefore described is almost identical to an existing stick of collagen casing except for the end closure 16. As mentioned above, the end closure consists of a fully heat sealed portion 16 with one part sealed at a higher temperature and a partially heat sealed transition portion 18. In use, the shirred collagen casing stick 10 is loaded into the high speed Handtmann sausage filling machine in the usual manner.

Reference is now made to Fig. 7 of the drawings which depicts a side view of part of the apparatus of the Handtmann filling machine showing the chuck and voiding components. The leading of a shirred stick 10 of casing is partially filled with meat emulsion injected via hollow tube or meat horn 80. The filled tube 81 passes through the chuck 82 and voiders 84 and into the belt transport 86 system of the sausage filling apparatus. The continuous pump of the high speed filling machine injects meat emulsion sufficient to propel the filled casing at a velocity such that 1200-1500 links per minute can be formed. As soon as the leading portion of the meat emulsion contacts the transition area 18, this causes the transition area to separate relatively slowly and thus dissipate the effect or impact of the force of the meat emulsion thus lessening the effect of this force on the end closure 16. This results in the end closure 16 being able to accommodate the force without tearing and be propelled forward in the desired direction by the force. As will be seen in Fig. 2 of the drawings, the end closure 16 has a smooth leading edge 20 and there is no twist involved in the closure. This means that in response to the projectile force of the meat emulsion, the trajectory of the leading end does not substantially deviate from the desired path but passes from the chuck 82 and through the rotating voiders 84 to enter the belt transport system 86 where the sausage is transported by means of a pair of opposed belts 88a, 88b. As is well known in the art, the voiders are contra-rotating plates which nip or pinch the filled rope of casing to create a crimp 90 each time they contact the casing which defines the length of a link.

The end closure hereinbefore described permits use of the high speed filling apparatus as its intended speed, that is around 1200-1500 links per minute with minimal disruption to the filling and linking operation caused by the end closure itself.

Various modifications may be made to the embodiments hereinbefore described without departing from the scope of the invention. For example, the end closure may be applied to edible shirred tubular food casings or materials other than collagen. Trimming of the gelatinised portion or the end closure portion may be achieved by means other than a blade, for example a laser or ultrasound. The heating blocks and insulating blocks may be selected as appropriate in order to achieve a suitable thermal gradient over the length of the end closure. The insulating blocks may be of any suitable cross-section to provide a suitable thermal gradient applied to the flattened collagen casing. In addition, a single heater block may be used and heated to a temperature of 225°C or other temperature as appropriate. The process times and temperature may be varied depending on the particular seal requirements. The ratio of size between the insulated and non-insulated portions of the heating blocks may be varied allowing tailoring of end closure configuration to a particular customer application. The smooth cut edge need not be perfectly smooth and perpendicular although an angle close to perpendicular is desired. The edge should be substantially smooth and angled sufficiently to have minimal influence on the trajectory of a filled sausage casing when projected through a high speed filling machine. A non-stick heat resistant tape may be used to cover the faces 94a, 94b (in shading) of the heating blocks 52a, 52b as shown in Fig. 4. The tape 92 facilitates release of the solidified and gelatinised collagen from the heater blocks.

The end closure, the method and apparatus according to the invention offer a number of advantages. Firstly, with regard to the end closure no twisted casing buffer is necessary to ensure straight filling of the first sausage and correct entry to the belt transport system or the filling machine. The end closure results in improved end closure and improved machinability . The use of the transition also results in a novel method of absorbing kinetic energy of the meat during the filling of the first sausage. The apparatus is dimensioned in proportion to allow it to fit into existing shirred tubing production machinery. The end closure produced by the above method is a flat seal without any twisting where the first, or transition, portion of the end closure is produced at a lower temperature which is intended as a sacrificial portion to absorb kinetic energy of projected meat emulsion. The remaining heat sealed portion of the end closure is produced at the higher temperature and provides full mechanical strength required to withstand the internal pressure of the fully formed sausage in the high speed filling machine. The absence of twisting minimises the tendency of the filled sausage to deviate during the filling process in the high speed machine .

Claims

1. A shirred casing stick having an untwisted leading end with an end closure of sufficient length to retain meat emulsion injected into the casing, the leading end terminating in a substantially smooth edge transverse to the longitudinal axis of the shirred casing stick.

2. A casing stick as claimed in claim 1 wherein the smooth edge is substantially perpendicular to the longitudinal axis of the shirred casing stick.

3. A casing stick as claimed in claim 1 or claim 2 wherein the shirred casing stick end closure is created by applying heat and pressure over a portion of the casing length to form a flattened gelatinised portion with excess casing distal to the flattened portion being removed, and then allowing the gelatinised portion to cool and solidify to leave the end closure.

4. A casing stick as claimed in any preceding claim wherein a transition portion is provided between the heat sealed end closure portion and the shirred casing, the transition portion being partly heat sealed which is sufficient to receive the impact of meat emulsion as the casing is filled such as to buffer the force of the emulsion during filling and thus minimise the impact of the meat emulsion on the end closure.

5. A casing stick as claimed in claim 4 wherein the fully heat sealed portion is provided adjacent the transition portion.

6. A casing stick as claimed in claim 4 wherein the end closure portion is about 20 mms in length and the transition portion is about 10 mms in length, irrespective of the diameter of the shirred casing.

7. A casing stick as claimed in claim 5 wherein the transition portion is about 25 mm in length and the fully heat sealed portion is about 10 mm in length (?) .

8. A shirred collagen casing stick having an end closure at a leading end thereof for retaining meat emulsion injected into said shirred casing, said end closure having a first heat seal portion with a substantially smooth leading edge and a second heat seal portion disposed between said first heat seal portion and said shirred casing, said second heat seal portion being adapted to separate in response to the force of said injected meat emulsion for buffering the force on said end closure .

9. A method of manufacturing an end closure on the leading end of a stick of shirred collagen casing, said method comprising the steps: extending the leading end of said shirred casing to form an extended portion, flattening an extended portion over a pre-determined length of the extended portion, heating the flattened length to gelatinise the flattened point and then allowing the gelatinised portion to cool and solidify to create an end closure portion and to create a transition portion between the end closure portion and the stick of shirred casing, and cutting the flattened casing at the distal end of the end closure portion to remove excess casing and to provide a smooth edge to said end closure portion.

10. A method as claimed in claim 9 wherein the method of manufacturing said end closure includes applying heat and pressure to gelatinise said casing over the length of said flattened portion.

11. A method as claimed in claim 9 or 10 wherein said method includes applying heat and pressure to said flattened portion for a pre-determined time to ensure that all of the flattened portion is substantially gelatinised prior to cooling.

12. A method as claimed in claim 11 including the step of forming a transition portion between the shirred casing and the heat treated portion.

13. A method as claimed in claim 12 including the step of heating the flattened portion over a first predetermined length at a first temperature to form said transition portion and heating the flattened portion over a second pre-determined length at a second temperature higher than said first temperature to form a fully heat sealed portion, said second pre-determined length being adjacent to said first pre-determined length.

14. Apparatus for creating an end closure on shirred collagen casing stick, said apparatus comprising, inserting means for coupling to the leading end of a shirred collagen casing stick, said inserting means being moveable from a first position to engage with said leading end of the collagen casing stick to a second position wherein said leading end of said collagen casing stick is extended for subsequent treatment by said apparatus , casing clamp means for clamping said extended collagen casing leading end in position, heating and cutting means for flattening said clamped casing and for heating the clamped casing to a pre-determined temperature to heat seal said flattened collagen casing into an end closure and for cutting said casing to provide a substantially smooth cut edge on said leading end when said casing is in said clamped third position, said insertion means being moveable to said first position to re-insert said completed end seal into said shirred collagen casing stick.

15. Apparatus as claimed in claim 14 wherein said apparatus includes removing means for removing the cut portion of said casing held by said clamp means.

16. Apparatus as claimed in claim 14 wherein said removing means includes clamp actuation means coupled to said casing clamp means for moving said clamped casing to a third position where excess casing is torn from said cut portion for subsequent removal.

17. Apparatus as claimed in claim 14, 15 or 16 wherein said insertion means includes a cam surface such that when said insertion means is moved from said first to said second position, said cam surface actuates said casing clamp means to clamp the extended casing in the second position.

18. Apparatus as claimed in any one of claims 14 to 17 wherein said insertion means is reciprocally moveable by bi-directional clamp actuation means provided by a double-acting piston.

19. Apparatus as claimed in any one of claims 14 to 18 wherein said clamping means is provided by a pair of jaws coupled to the leading end of arms mounted on pivots, said arms being engageable with said cam surface.

20. Apparatus as claimed in any one of claims 14 to 19 wherein said heating means is provided by two heating blocks, said heating blocks being coupled to an electrical energy source for raising said blocks to a pre-determined temperature.

21. Apparatus as claimed in claim 20 wherein each of said heating blocks include a recess into which is inserted an insulator to minimise the heat applied to said clamped casing sandwiched between the insulators and create a closure transition zone in the end closure.

22. Apparatus as claimed in claim 20 or 21 wherein the or each heater block comprises at least two separate block elements, said heater block elements being energisable to different temperatures.

23. Apparatus as claimed in claim 22 wherein two separate heater block elements are separated by an insulator strip.

24. Apparatus as claimed in claim 23 wherein there are two separate heater block elements in each heater block.

25. Apparatus as claimed in any one of claims 14 to 24 wherein the movement of the double acting piston, the pneumatic cylinders and the heat crimping and cutting is controlled via a programmable logic control unit .