WO2001091564A1

WO2001091564A1 - Apparatus and method of making an encased product

Info

Publication number: WO2001091564A1
Application number: PCT/GB2001/002459
Authority: WO
Inventors: Klaus-Peter Kreibig
Original assignee: Devro-Teepak Limited
Priority date: 2000-06-02
Filing date: 2001-06-01
Publication date: 2001-12-06
Also published as: GB0013505D0; AU6250901A

Abstract

There is disclosed an apparatus and a method of making encased products, particularly sausages. In a preferred embodiment the apparatus (10) comprises a hollow member (12) connected to a supply of a flowable medium such as a meat emulsion, a restriction element (14) with one end located adjacent a discharge outlet (16) of the hollow member (12) and the other free end (36) defining a face (38) substantially transverse to a direction of flowable medium flow, and a tubular element (18) disposed around the restriction element (14) to define a substantially annular flow passage (42) therebetween. The flowable medium is extruded through the hollow member (12), through the annular flow passage (42) and over the free end (36) of the restriction element (14), when it is urged radially inwardly, to underfill a casing (40) which is shirred around the outer surface of the tubular element (18). Other embodiments of the invention are discussed.

Description

APPARATUS AND METHOD OF MAKING AN ENCASED PRODUCT

The present invention relates to apparatus and a method of making an encased product. In particular, but not exclusively, the present invention relates to apparatus and a method for extruding a length of a flowable medium, such as a meat emulsion product, into a shirred meat casing.

Sausage links are often manufactured by first extruding a flowable product, termed a meat "emulsion" and comprising a sausage meat into a "shirred" (or folded) meat casing, using a meat stuffing horn, to create a filled meat casing. A secondary link forming process is then carried out on the filled sausage, such as tying, twisting or crimping. In certain circumstances, the extrusion and the link forming process is carried out in a single step using one dual function machine, such as is disclosed in U.S. Patent No. 4,187,583, assigned to Townsend Engineering Company. U.S. Patent No. 4,187,583 discloses a product encasing machine including a rotatable stuffing tube having a folded casing mounted thereon. The product is pumped or moved through the interior of the stuffing tube into the casing. A restrictor apparatus is secured to the stuffing tube and is positioned within the casing being filled downstream of the discharge end of the stuffing tube, to spread and increase the pressure in the stuffed casing. The rotating restrictor applies torque to the sausage from the inside of the casing to impart torque thereto and causes a rotational drive to the product so that a link is formed by the twisting of the casing. There are different types of meat casings which are used to manufacture sausages . Natural meat casings are one such type and offer a number of advantages, such as flexibility,^' and a relatively high water content providing a low coefficient of friction. This allows meat product extruded into such natural casings to easily move therein, allowing, for example, tying operations to be carried out (manually or by machine) to form the sausage links .

However, natural casings are not suitable for use in high speed operations, mainly because natural casings, being manufactured from animal intestine, are a limited resource. Furthermore, natural casing dimensions and strengths vary from casing to casing. Such disadvantages are unacceptable in high speed operations, where cased product is produced at a relatively high speed, which would quickly use up a short length of natural casing. Furthermore, the casing parameters (length, diameter and strength) from casing to casing must be reasonably consistent to allow high speed operations to be conducted. Therefore, shirred collagen casings are used.

Collagen casings suffer from some disadvantages such as having high coefficients of friction, causing adhesion of meat products to the casing wall. This can cause the casing to soften, as collagen casing has a short "wet- out" (the time in which the casing absorbs moisture and becomes soft) . This means that secondary link forming procedures (such as tying) cannot readily be performed, as the casing is often damaged and splits. This is a particular problem in high speed operations, where such breakage may cause a relatively high product loss and down-time while any resultant spillage is cleaned. Consequently, collagen cased sausages are often formed into individual sausages by crimping and cutting the extruded product.

It is amongst the objects of the present invention to obviate or mitigate at least one of the foregoing disadvantages .

According to a first aspect of the present invention, there is provided an apparatus for extruding an encased flowable medium, the apparatus comprising -. a hollow member for supplying a flowable medium to be encased; a restriction element of a predetermined length located adjacent a discharge outlet of the hollow member, and having a free end defining an end face substantially transverse to a direction of flowable medium flow, and a tubular element disposed around the restriction element, to define a substantially annular flow passage between an inner surface of said tubular element and an outer surface of the restriction element, for extruding the flowable medium from said annular flow passage into a casing.

According to a second aspect of the present invention, there is provided apparatus for extruding an encased flowable medium, the apparatus comprising : a hollow member for coupling to a chamber having a flowable medium therein and for supplying said flowable medium to be encased; a restriction element of a predetermined length, located adjacent a discharge outlet of the hollow member, and having a free end defining an end face substantially transverse to a direction of flowable medium flow, and a tubular element disposed around the restriction element, to define a substantially annular flow passage between an inner surface of said tubular element and an outer surface of the restriction element; whereby the flowable medium is extruded through the annular flow passage and over the free end of the restriction element, where it is urged radially inwardly, to underfill a casing. This advantageously allows an encased flowable medium, such as meat emulsion, to be extruded wherein the casing, when filled, is "understuffed" , such that the internal cross-sectional area of the casing, when unfilled, is greater than the cross-sectional area of the extruded meat emulsion. This allows for movement of the meat emulsion within the casing to reduce adhesion of the emulsion to the casing wall and facilitate secondary operations such as tying or twisting to be carried out without causing excessive stresses/strains in the casing which may otherwise lead to rupture. Thus, the apparatus may advantageously allow an encased meat product to be extruded. The under- stuffing of the casing may facilitate performance of the secondary operation, as the understuffing may allow the meat emulsion to move within the casing. Also, the secondary operation may take up the slack in the casing of the understuffed encased meat emulsion without causing excess stress/strain in the casing, which may otherwise cause rupture.

Alternatively, the flowable medium may comprise a dough or the like.

Preferably, the casing comprises a collagen casing. Alternatively, the casing may comprise a natural or cellulose casing.

The hollow member may comprise an elongate stuffing tube coupled to a chamber having a flowable medium therein. Conveniently, the hollow member further comprises a convergent inlet, for directing flowable medium into the elongate stuffing tube from the chamber.

The restriction element may comprise a body having a first end located adjacent a discharge outlet of the hollow member. The body may be circular in cross- section and may be of a substantially constant external diameter. Preferably, the first end of the restriction element body tapers towards the discharge outlet of the hollow member, to facilitate flow of emulsion from the hollow member to the restriction element. Where the body is of a substantially constant external diameter, the free end comprises a second end opposite said first end of the body.

Alternatively, the body may comprise a first portion of a first external diameter and a second portion of a second, greater external diameter. The body may be tapered at a junction between the first and second body portions to facilitate flow of emulsion over the restriction element. The junction between the first and second portions may be disposed adjacent a discharge outlet of the tubular element. Conveniently, the free end of the restriction element comprises the end of the second body portion. The end face of the restriction element may be substantially perpendicular to the direction of emulsion flow. Alternatively, the end face may be convex or concave . The restriction element may be hollow and may be tubular. Alternatively, the restriction element may be substantially solid. Conveniently, the restriction element is located adjacent the discharge outlet of the hollow member by a mounting member extending through the hollow member. The mounting member may comprise an elongate rod. Preferably, the restriction element is coupled to the hollow member by the rod. The rod may have a threaded end for engaging a corresponding threaded bore of the restriction element. Alternatively, the rod may be coupled to the restriction element by welding or otherwise securing the rod thereto or, in a further alternative, the rod may be formed integrally with the restriction element. In a further alternative, the restriction element may be coupled to the tubular element by mounting fins or the like extending inwardly from a wall of the tubular element. Where the restriction element is hollow, the restriction element may define a bore extending therethrough having an inlet in the end face of the free end thereof. Conveniently, the bore is in communication with evacuation apparatus for creating a vacuum at the bore inlet. The mounting member may be a hollow tube having an internal bore for coupling the restriction element bore to the evacuation apparatus. Preferably, the mounting member is coupled to the tube which is, in turn, coupled to the hollow member by fins or the like extending inwardly from a wall of the tubular element . The tubular element may comprise a tube coupled to the hollow member adjacent the discharge outlet thereof. Conveniently, the tubular element is of a low friction material such as poly-tetra-fluoro-ethylene (PTFE) , to allow shirred casing to be supported upon the hollow member and the tubular element, and to allow the shirred casing to move freely over the tubular element during extrusion of the flowable medium.

Flow of the flowable medium over the restriction element free end may reduce the pressure at the free end. However, the pressure may be further reduced at the free end bore inlet of the hollow restriction element by creating a vacuum. Reducing the pressure at the free end may create a vacuum, to cause the flowable medium passing over the restriction element free end to be urged radially inwardly to assume a cross-sectional area less than an unfilled cross-sectional area of the casing. Where the flowable medium is a meat emulsion, such as may be used to form meat sausages, an extruded encased sausage of a relatively large cross-sectional area may require the pressure at the free end bore inlet to be reduced using the evacuation apparatus in order to avoid creation of an internal bore or trapped air occurring in the extruded, encased sausages. A sausage of relatively large cross-sectional area may have an average diameter greater than 38mm.

According to a fourth aspect of the present invention, there is provided a method of extruding an encased flowable medium, the method comprising the steps of : supplying a flowable medium to be encased through a hollow member; discharging the flowable medium from a discharge outlet of the hollow member and over a restriction element of a predetermined length; extruding the flowable medium along a substantially annular flow path defined between an inner surface of a tubular element disposed around the restriction element and an outer surface of said restriction element; discharging the flowable medium from the restriction element and into a casing; and reducing pressure in the vicinity of a free end of the restriction element so that the casing is understuffed by the flowable medium.

Embodiments of the present invention will now be described, with reference to the accompanying drawings, in which:

Fig. 1 is a diagrammatic illustration of apparatus for extruding an encased meat emulsion in accordance with a first embodiment of the present invention;

Fig. 2 is a diagrammatic illustration of apparatus for extruding an encased meat emulsion in accordance with a second embodiment of the present invention;

Fig. 3 is a diagrammatic illustration of apparatus for extruding an encased meat emulsion in accordance with a third embodiment of the present invention; Fig. 4 is a diagrammatic illustration of apparatus for extruding an encased meat emulsion in accordance with a fourth embodiment of the present invention;

Fig. 5 is a diagrammatic view of the apparatus of Fig. 1 for illustrating test parameters Dl to D5 of the apparatus tested;

Fig. 6 is a table listing the test parameters Dl to D5, shown in Fig. 5, for two types of the apparatus of Fig. 1, having different test parameters Dl to D5, and

Fig. 7 is a table listing test results of the two types of apparatus having the test parameters Dl to D5 in the table of Fig. 6 used for extruding meat emulsion into two types of casing.

Referring firstly to Fig. 1, there is shown an apparatus for extruding an encased flowable medium, such as a meat emulsion, in accordance with a first embodiment of the present invention, indicated generally by reference numeral 10. The apparatus is commonly referred to in the art as a "stuffing horn".

The stuffing horn 10 generally comprises a hollow member in the form of a stuffing tube 12, a restriction element 14 located adjacent a discharge outlet 16 of the stuffing tube 12 and a tubular element in the form of a cover tube 18, coupled to the stuffing tube 12 and located around the restriction element 14.

The stuffing tube 12 is a hollow, elongate body and has a convergent inlet 20, by which the stuffing tube 12 is coupled to a supply of meat emulsion, such as a meat emulsion product used in the manufacture of sausages. The meat emulsion is stored in a chamber 21 (partially shown in broken outline) having an outlet 21a coupled to the tube inlet 20. The convergent inlet 20 directs the meat emulsion into and along the stuffing tube 12 in the direction of arrow A. In the following description, reference is made to the extrusion of a meat emulsion product. However, as will be appreciated by persons skilled in the art, the apparatus herein described may equally be used for extruding an alternative encased flowable medium, such as a dough or other such product which generally retains the shape of the die that the product is forced through. The term "meat emulsion" means a paste of ground-up meat of the type commonly used to make sausages.

A mounting member in the form of a hollow tube 48 defining an internal bore 50 extends through the stuffing tube 12 and is coupled thereto in the convergent inlet 20 by mounting fins 52, which are of a narrow profile so as to cause minimal obstruction to flow of meat emulsion.

The restriction element 14 is an elongate body comprising a cylinder of a single external diameter and is itself hollow, defining an internal bore 56. The hollow tube 48 is threaded at an end 54 thereof, so that bore 50 is arranged to mate with the corresponding threaded bore 56 of the restriction element 14. The restriction element 14 is disposed within the cover tube 18 such that the restriction element 14 protrudes beyond a discharge outlet 26 of the cover tube 18. The restriction element 14 has a conical or tapered end 32 located adjacent the discharge outlet 16 of stuffing tube 12, which end 32 converges towards the discharge outlet 16. The tapered end 32 of the restriction element 14 allows for smooth passage of the meat emulsion over the restriction element 14, without causing excessive pressure build-up which could damage the stuffing horn 10 or a meat casing, or lead to separation of fat from the meat, producing "smearing" in the sausages.

A free end 36 of the restriction element 14 has an end face 38 substantially transverse to the direction of meat emulsion flow through the stuffing horn 10. When the meat emulsion is passed at speed past end face 38, a pressure drop is created and this causes the meat product to implode radially inwardly at the free end 36, to form a length of extruded meat product of a desired first cross-sectional area, as will be later described. To ensure that there are minimal voids within the meat in the final sausage, the internal bore 56 of the restriction element 14 is coupled to internal bore 50 of hollow tube 48, which is, in turn, connected via a vacuum tube 58 to evacuation apparatus comprising a vacuum pump (not shown) . This allows the pressure at the end face 38 to be reduced, to create a vacuum within the meat emulsion extruded from the free end 36 of restriction element 14. This vacuum collapses any internal air tube or air voids created within the extruded encased meat emulsion, to improve appearance and reduce oxidation of the meat. Furthermore, this allows sausages of a relatively larger cross-sectional area to be extruded, which require a restriction element 14 of a greater external diameter, and which may otherwise produce such an internal air tube or air voids.

A shirred collagen meat casing, part of which is shown in Fig. 1 and indicated by the reference numeral 40, is pre-inflated and mounted over the stuffing tube 12 and cover tube 18. The cover tube 18 is coupled to the end of the stuffing tube 12 adjacent the discharge outlet 16 by a bayonet lock fitting (not shown) . An annular flow path 42 for the meat product is defined between an outer surface 44 of the restriction element 14 and an inner surface 46 of a wall 30 of the cover tube 18.

In use, the meat emulsion is extruded along the stuffing tube 12 in the direction of the arrow A and is discharged from the discharge outlet 16. Meat product extruded from the discharge outlet 16 passes over the tapered end 32 of inner element 22 as shown by the arrow B and travels along the annular flow path 42 in the direction of the arrow C. The velocity of the meat product in the annular flow path 42 is greater than that in the stuffing tube 12 and, furthermore, the pressure of the meat product in the annular flow path 42 is less than that in the stuffing tube 12.

The meat emulsion is then extruded from the discharge outlet 26 and enters the casing 40. Friction between the meat emulsion and the casing wall causes the shirred (or folded) casing 40 to be pulled from the cover tube 18. The high speed of the meat emulsion deshirrs the casing 40 from cover tube 18, but does not inflate the casing. The cover tube 18 is typically manufactured from a low friction material, such as PTFE, to facilitate deployment of the casing 40.

Upon reaching the free end 36, low pressure at the end face 38 causes the meat emulsion to collapse radially inwardly, slowing the emulsion down and causing it to increase in pressure, to fill the casing 40 and extrude a length of the meat emulsion into the casing 40. The meat emulsion extruded into the casing 40 is of a first cross-sectional area which is less than the cross- sectional area of the casing 40, so that the casing 40 is underfilled and is said to be "understuffed" . Where a collagen casing 40 is used, the extruded encased meat emulsion can now undergo a secondary finishing process, such as tying or twisting, without causing rupture of the casing 40, because the understuffing of the casing 40 allows for the twisting or tying operation to be carried out without causing excessive shear stresses or strains within the casing 40, which could otherwise lead to rupture. Furthermore, collagen has a relatively quick "wet-out" when a meat emulsion is in contact with the casing wall, which can quickly lead to the casing absorbing moisture and becoming weak. Understuffing of the casing 40 with the meat emulsion reduces this disadvantage, as the casing 40 is not stretched to enclose the meat emulsion.

Referring now to Fig. 2, there is shown a diagrammatic illustration of apparatus for extruding an encased emulsion, in accordance with a second embodiment of the present invention, in which like components share the same reference numerals except incremented by 100.

Thus the stuffing horn 110 comprises a stuffing tube 112, restriction element 114 and cover tube 118. The stuffing tube 112 includes a convergent inlet 120 coupled to a supply of meat emulsion contained in a chamber 121 (partially shown in broken outline) in the same fashion as stuffing tube 12. The restriction element 114 is a generally solid body and comprises a first body portion in the form of an inner cylindrical element 22, of a first external diameter, and a second body portion in the form of an outer cylindrical element 24, of a second external diameter greater than the first external diameter of the inner element 22. The restriction element 114 is disposed within the cover tube 118 such that the outer element 24 protrudes beyond a discharge outlet 126 of the cover tube 118. The restriction element 114 has a conical end 132 located adjacent a discharge outlet 116 of the stuffing tube 112, which end 132 converges towards the discharge outlet 116. In a similar fashion, a junction 34 between the outer element 24 and the inner element 22 converges in a direction towards the end 132 of the restriction element 114. Both the end 132 and the junction 34 of the restriction element 114 allow for smooth passage of the meat emulsion over the restriction element 114.

The restriction element 114 is coupled to the cover tube 118 by fins 28, which extend inwardly from a wall 130 of the cover tube 118. The fins 28 are of a relatively thin profile so as to cause minimal obstruction to flow of meat emulsion through the stuffing horn 110, as will be described in more detail below.

The cover tube 118 is coupled to the stuffing tube 112 and is secured by a bayonet fitting 41, like the structure of Fig. 1. An annular flow path 142 is defined between an outer surface 144 of inner element 22 and an inner surface 146 of the wall 130 of the cover tube 118. The element 114 has an end face 138 which is substantially orthogonal to the flow direction.

A meat emulsion is supplied along the stuffing tube 112 in the direction of the arrow A, in a similar fashion to the stuffing horn 10 of Fig. 1 and is discharged from the discharge outlet 116 of stuffing tube 112 and into the annular flow path 142. The meat emulsion travels along the annular flow path 142 in the direction of the arrow B, before discharging from a discharge outlet 126 of the cover tube 118, where the meat emulsion passes over the tapered junction 34 between inner and outer elements 22 and 24, travelling in the direction of the arrow C. The meat emulsion then travels over the outer surface of the outer element 34 and, upon reaching the free end 136, low pressure at the end face 138 causes the meat emulsion to collapse radially inwardly in the direction of arrow D, filling the shirred casing 140.

As with the embodiment of Fig. 1, the meat emulsion passing over the free end 136 of restriction element 114 results in an understuffed casing.

Referring now to Fig. 3, there is shown a diagrammatic illustration of apparatus for extruding an encased emulsion, in accordance with a third aspect of the present invention, in the form of a stuffing horn 210, similar to the stuffing horn 10 of Fig. 1. Fig. 3 shows only part of the stuffing horn 210, the remaining components being the same as those shown in Fig. 1. Like components share the same reference numerals as those of Fig. 1 except incremented by 200.

The stuffing horn 210 differs from the stuffing horn 10 in that the cover tube 218 is tapered at an end 60 thereof and includes a radially inwardly extending shoulder 62, for engaging the discharge outlet 216 of stuffing tube 212, only part of which is shown. The cover tube 218 is secured to the stuffing tube 212 using a bayonet fitting (not shown) . The restriction element 214 is mounted in the cover tube 218 by fins 228 and comprises a first body portion in the form of an inner cylindrical element 222 and a second body portion in the form of an outer cylindrical element 224, similar to the inner and outer elements 22 and 24. However, the free end 236 of the outer element 224 has an end face 238 which is convex, rather than perpendicular to the direction of emulsion flow. This is advantageous because during extrusion of an encased emulsion, the encased emulsion leaving the end face 238 hangs down under gravity and it has been found that the casing 240 rests against the top 239 of the outer element 224. Making the end face 238 convex smooths the edge of the element 224 to reduce the likelihood of casing fracture. Referring now to Fig. 4, there is shown a diagrammatic illustration of apparatus for extruding an encased emulsion in accordance with a fourth embodiment of the present invention, in the form of a stuffing horn 310. Like components share the same reference numerals as those of Fig. 1 except incremented by 300.

The stuffing horn 310 is similar to the stuffing horns 10, 110 and 210 of Figs. 1, 2 and 3, except that the stuffing horn 310 includes a restriction element 314 which comprises a solid cylinder of a defined external diameter. The restriction element 314 does not include an outer cylindrical element 24, as does the restriction element 114 of stuffing horn 110. The restriction element 314 is mounted to a wall 330 of a cover tube 318 by fins 328 and includes a conical end 332. An annular flow path 342 is defined between an outer surface 344 of the restriction element 314 and an inner surface 346 of the cover tube 318. The restriction element has an end face 338 which is orthogonal to the direction of flow. In this fashion, meat emulsion extruded from the stuffing tube 312 in the direction of the arrow A passes over the conical end 332 and flows through the annular flow path 342 in the direction of the arrow B. The meat emulsion is then discharged from a discharge outlet 326 of the cover tube 318 into the casing 340, as shown by the arrow C. The sausage is understuffed in the same fashion as for the embodiments described above. Referring now to Figs. 5 to 7, Fig. 5 is a diagrammatic view of the stuffing horn 110 of Fig. 2 for illustrating test parameters Dl to D5 of the stuffing horn tested; Fig. 6 shows a table listing the test parameters Dl to D5, shown in Fig. 5, for two types of stuffing horn 110 of Fig. 2, having different test parameters Dl to D5; and Fig. 7 shows a table listing test results for the two types of stuffing horn 110 having the test parameters Dl to D5 in the table of Fig. 6 used for extruding meat emulsion into two types of casing.

As shown in Fig. 5, the outer diameter of the cover tube 118, outer diameter of inner element 22, outer diameter of outer element 24, inner diameter of cover tube 118 and the depth of the annular flow path 142 are denoted by reference numerals Dl to D5, respectively.

Turning now to Fig. 6, column 1 of the table defines the test parameters Dl to D5 ; column 2 lists the dimensions of the corresponding components for a first type of the stuffing horn 110; and column 3 lists the dimensions of the corresponding components for a second type of the stuffing horn 110. The tests were conducted according to the parameters set out in the table of Fig. 6 with casings of two different types, as will be described with reference to Fig. 7. Each casing type was of an approximate unstuffed casing diameter of 38mm. As seen in the table of Fig. 6, the first type stuffing horn 110 comprised a cover tube 18 with an outer diameter Dl of 34mm and an inner diameter D4 of 31.5mm. The inner element 22 had an external diameter D2 of 14mm and outer elements 24 of outer diameters D3 of 16mm, 18mm and 20mm were tested. The corresponding depth of the annular flow path 142 for each of the outer elements 24 is listed in the bottom three rows of the table in Fig. 6.

Turning now to Fig. 7, column 1 indicates test results carried out on the type 1 and type 2 cones for respective cone diameters of 16, 18 and 20mm. Columns 2 to 4 indicate the test results of the stuffing horn 110 of the first type with outer cone 24 diameters of 16, 18 and 20mm, whilst columns 5 to 7 indicate the test results for the stuffing horn 110 of the second type with outer cone 24 diameters of 16, 18 and 20mm, respectively. For each diameter, the stuffing horns 110 were tested with casings 40 of two different types, given the product specifications Coria and CUP respectively. The Coria- type casing was a casing which was "dry" stuffed, without any additional fluid, whilst the CUP casing was stuffed "wet", to achieve maximum flexibility of the casing.

Row A lists the understuffed diameter of the extruded casing before undergoing a finishing operation, in this case, tying; rows B to E indicate the diameter of the extruded product after tying to form sausage links of determined lengths and the length of the sausage links; and row F indicates the presence of any holes in the extruded, tied product following cooking. It will be understood that when the extruded product is tied into links of a determined length, the meat emulsion is "squeezed" and the casing reduces in volume, causing the meat to expand radially.

Considering the type 1 test results for the 16mm outer diameter outer cone 24, the results of which are listed in column 2, it will be seen that for the Coria- type casing 140, an encased product was extruded of average diameter 32.5mm. The encased product, when extruded, is oval or elliptically shaped in cross- section. The average diameter is therefore obtained by measuring the extruded product across its greatest diameter (39mm) and its least diameter (26mm) , at 90° around the casing, before averaging these diameters to obtain the value 32.5mm. The results in rows B to E indicate the diameter of the product following tying for predetermined sausage link lengths. Thus, for links of 90mm length (column 2 results) , a stuffed diameter of 39mm was obtained; for a length of 105mm, a stuffed diameter of 38mm was achieved; and for a length of 130mm, a stuffed diameter of 37.5mm was achieved. It was found that, following frying, bores of up to 2mm diameter were found in the cooked, extruded sausages.

Similar operations were carried out for the CUP casing 140 with the stuffing horn 110 of type 1 including an outer cone 24 of 16mm outer diameter and, indeed, for the other stuffing horns with the component dimensions listed in Fig. 6, as noted above.

It has been determined that for an unstuffed casing of approximately 38mm diameter, an ideal stuffed diameter, following a finishing process (such as tying) , is in the range of 37mm to 39mm for any given sausage link length.

Thus, for the type 1 stuffing horn 110, with outer cone 24 diameter 16mm and with Coria-type casing, good results were achieved for sausage link lengths of 105mm, where the sausage links were of a stuffed diameter of 38mm. However, for the type 1 stuffing horn 110, outer cone 24 diameter 18mm with the Coria-type casing, sausage link lengths of 110mm produced stuffed link diameters of 36mm, which was found to be bordering on unsatisfactory results. The same set up with the CUP casing, however, and with sausage link lengths of 120mm, produced satisfactory results with stuffed sausage link diameters of 37.5mm.

Generally speaking, it has been found that satisfactory results are achieved using the stuffing horn 110 of the first type with the Coria-type casing. Furthermore, it has been found that to obtain satisfactorily stuffed, relatively short sausage links, the type 1 stuffing horn 110, with a cover tube 118 of greater inside diameter (D4) produces better results. This is because the cover tube 118 of type 1, with a greater inside diameter (D4) increases the depth (D5) of the flow path 142, producing sausage links well stuffed generally to 2mm greater outer diameter than for the type 2 stuffing horn.

It will be appreciated by persons skilled in the art that in the extrusion of an encased product, such as an encased meat product discussed above, an amount of manual skill may be required to achieve the desired stuffing.

It has been noted that the parameters affecting extrusion of the encased meat product include the diameter of the restriction element relative to the cover tube inside diameter. However, the compression of the meat emulsion on the outer element 24 is also important in determining the dimensions of the extruded sausages . It has also been found that the outer cone should not be of a length greater than, generally speaking, 100mm, otherwise the meat emulsion slows too soon, increasing in pressure, tending to fracture the casing.

Various modifications may be made to the foregoing within the scope of the present invention.

In particular, the restriction element 114 of stuffing horn 110 and/or the restriction elements 214 and 314 of stuffing horns 210 and 310 may be hollow and may define internal bores for coupling the respective restriction element to a vacuum pump in a similar fashion to the restriction element 14 of stuffing horn 10. Alternatively, the restriction element 114 of horn 110, restriction element 214 of horn 210 and/or the restriction element 314 of horn 310 may be mounted using a mounting member in the form of a solid rod, having a threaded end for engaging a corresponding threaded bore of the respective restriction element. The rod may alternatively be coupled to the restriction element by welding or otherwise securing the rod thereto, or the rod may be formed integrally with the restriction element .

The end face of the restriction element may be concave or any other suitable profile for causing the meat emulsion to collapse and create an understuffed sausage. The bayonet fitting may be replaced by any other suitable fastening means, such as screws, mounting pins or the like.

Claims

1. Apparatus for extruding an encased flowable medium, the apparatus comprising : a hollow member for supplying a flowable medium to be encased; a restriction element of a predetermined length located adjacent a discharge outlet of the hollow member, and having a free end defining an end face substantially transverse to a direction of flowable medium flow, and a tubular element disposed around the restriction element, to define a substantially annular flow passage between an inner surface of said tubular element and an outer surface of the restriction element, for extruding the flowable medium from said annular flow passage into a casing.

2. Apparatus for extruding an encased flowable medium, the apparatus comprising : a hollow member for coupling to a chamber having a flowable medium therein and for supplying said flowable medium to be encased; a restriction element of a predetermined length, located adjacent a discharge outlet of the hollow member, and having a free end defining an end face substantially transverse to a direction of flowable medium flow, and a tubular element disposed around the restriction element, to define a substantially annular flow passage between an inner surface of said tubular element and an outer surface of the restriction element; whereby the flowable medium is extruded through the annular flow passage and over the free end of the restriction element, where it is urged radially inwardly, to underfill a casing.

3 Apparatus as claimed in claim 1 or 2, wherein the flowable medium is a meat emulsion.

4. Apparatus as claimed in claim 1 or 2 , wherein the flowable medium comprises a dough.

5. Apparatus as claimed in any one of the preceding claims, wherein the casing comprises a collagen casing.

6. Apparatus as claimed in any one of claims 1 to 4, wherein the casing comprises a natural or cellulose casing.

7. Apparatus as claimed in any one of the preceding claims, wherein the hollow member comprises an elongate stuffing tube coupled to a chamber having a flowable medium therein.

8. Apparatus as claimed in any one of the preceding claims, wherein the hollow member further comprises a convergent inlet, for directing flowable medium into the elongate stuffing tube from the chamber.

9. Apparatus as claimed in any one of the preceding claims, wherein the restriction element comprises a body having a first end located adjacent a discharge outlet of the hollow member.

10. Apparatus as claimed in claim 9, wherein the body is circular in cross-section and is of a substantially constant external diameter with a free end comprising a second end opposite said first end of the body.

11. Apparatus as claimed in any one of the preceding claims, wherein the first end of the restriction element body tapers towards the discharge outlet of the hollow member, to facilitate flow of emulsion from the hollow member to the restriction element.

12. Apparatus as claimed in claim 9 or 11, wherein the body comprises a first portion of a first external diameter and a second portion of a second, greater external diameter.

13. Apparatus as claimed in claim 12, wherein the body is tapered at a junction between the first and second body portions to facilitate flow of emulsion over the restriction element.

14. Apparatus as claimed in claim 13 , wherein the junction between the first and second portions is disposed adjacent a discharge outlet of the tubular element .

15. Apparatus as claimed in claim 12, 13 or 14, wherein a free end of the restriction element comprises the end of the second body portion.

16. Apparatus as claimed in any one of the preceding claims, wherein the free end of the restriction element comprises a face which is substantially perpendicular to the direction of flowable medium flow.

17. Apparatus as claimed in any one of the preceding claims, wherein the free end face of the restriction element is convex.

18. Apparatus as claimed in any one of the preceding claims, wherein the free end face of the restriction element is concave.

19. Apparatus as claimed in any one of the preceding claims, wherein the restriction element is hollow and tubular.

20. Apparatus as claimed in any one of claims 1 to 18, wherein the restriction element is substantially solid.

21. Apparatus as claimed in any one of the preceding claims, wherein the restriction element is located adjacent the discharge outlet of the hollow member by a mounting member extending through the hollow member.

22. Apparatus as claimed in claim 21, wherein the mounting member comprises an elongate rod and the restriction element is coupled to the hollow member by the elongate rod.

23. Apparatus as claimed in claim 22, wherein the elongate rod has a threaded end for engaging a corresponding threaded bore of the restriction element .

24. Apparatus as claimed in claim 22, wherein the elongate rod is coupled to the restriction element by welding or otherwise securing the rod thereto.

25. Apparatus as claimed in claim 22, wherein the elongate rod is formed integrally with the restriction element.

26. Apparatus as claimed in any one of claims 1 to 20, wherein the restriction element is located adjacent the discharge outlet of the hollow member and is coupled to the tubular element by mounting fins extending inwardly from a wall of the tubular element.

27. Apparatus as claimed in any one of claims 1 to 19 and 21 to 25, wherein the restriction element defines a bore extending therethrough having an inlet in the end face of the free end thereof.

28. Apparatus as claimed in claim 27, wherein the bore is in communication with an evacuation apparatus for creating a vacuum at the bore inlet .

29. Apparatus as claimed in any one of claims 1 to 25, 27 or 28, wherein the mounting member is a hollow tube having an internal bore for coupling the restriction element bore to the evacuation apparatus .

30. Apparatus as claimed in claim 29, wherein the mounting member is coupled to the hollow tube which is, in turn, coupled to the hollow member by fins or the like extending inwardly from a wall of the tubular element.

31. Apparatus as claimed in any one of the preceding claims, wherein the tubular element is coupled to the hollow member adjacent the discharge outlet thereof.

32. Apparatus as claimed in claim 31, wherein the tubular element is coupled to the hollow member by a bayonet fitting.

33. Apparatus as claimed in any one of the preceding claims, wherein the tubular element is of a low friction material such as poly-tetra-fluoro-ethylene (PTFE) .

34. Apparatus as claimed in claim 27 or 28, wherein the pressure at the free end bore inlet of the hollow restriction element is reduced by creating a vacuum.

35. Apparatus as claimed in claim 33, wherein the vacuum causes the flowable medium passing over the restriction element free end to be urged radially inwardly to assume a cross-sectional area less than an unfilled cross- sectional area of the casing.

36. A method of extruding an encased flowable medium, the method comprising the steps of : supplying a flowable medium to be encased through a hollow member; discharging the flowable medium from a discharge outlet of the hollow member and over a restriction element of a predetermined length; extruding the flowable medium along a substantially annular flow path defined between an inner surface of a tubular element disposed around the restriction element and an outer surface of said restriction element; discharging the flowable medium from the restriction element and into a casing; and reducing pressure in the vicinity of a free end of the restriction element so that the casing is understuffed by the flowable medium.