HK1230871A - End closure for an edible collagen casing and a method for obtaining thereof - Google Patents

Description

End closure for edible collagen casing and method for obtaining same

Technical Field

The invention applies in the meat sausage casing industry, and in particular in the field of the closing of shirred sausage casings, which is intended to enable the closing of shirred sausage casings to be done in a simpler manner without wasting too much casing material, can ensure that it withstands the powerful impacts of meat emulsion during filling, does not invade the internal medium of the casing tube and can give the finished product satisfactory properties which are able to allow the recovery of each batch of the first filled sausage together with the rest of the sausage produced, and at the same time, in particular in the edible collagen sausage market, which are consistent in edibility with casings made of natural raw materials. The invention should also be a closure, the manufacture of which is easily automated and can even be performed on-line on the same machine that shirrs the casing. This is why the material also requires a low melting temperature to prevent damage of the casing and a high bonding force for quick welding to obtain high application efficiency.

Background

The pre-closing of one end of the food casing is an essential step required for successful filling in a further filling process. A wide variety of end closure solutions are used in the food casing industry project to accomplish the manufacture of almost all food casings that are directly pourable in practice. This finishing stage includes the context of a wide range of processing operations, commonly referred to as "retooling," in which the casing in its flattened form is unwound from its original coiled state and then shirred or alternatively segmented, coated, looped with a rope sling, wrapped with an elastic gathering mesh, or stitched seams to produce longitudinal seams or final seals, etc., for eventual closure at one end.

For clarity, the following definitions are made:

casings are smooth and flexible hollow tubes formed from natural or artificial films, having a beginning and an end.

A section of casing (length) is a part of the casing, i.e. a section (stretch) of casing.

A string of casing is a section, portion or segment of twisted casing.

The terminal end (terminal) corresponds to the very end of the casing.

The strand portion (strand) is a rod (stick) or shirred and compact casing forming a circular hollow tube.

The aperture is the lumen of a hollow tube such as a strand portion or rod.

Different reforming operations are applied according to the type and purpose of the casing, but most of these are done by sealing the end of the casing, which is the first part of the sausage to be formed and which will be subjected to the earliest impacts of the meat emulsion entering at a certain speed through the filling horn of the filling machine. Therefore, the seal must be able to withstand the kinetic energy transferred by the incoming mass without opening or breaking.

Most closure solutions are intended to form a seal by the casing material itself without introducing other foreign elements into it. Those sealing processes appear to be easy to work with; the machinery used to implement the process is in fact quite complex. Above, from an engineering and construction point of view, operations that are simple for the human hand become a difficult task when intended to be transferred to a machine.

The end closure, which is constituted by the casing material itself, usually uses a cut of shirred casing from the end of a strand of shirred casing, which is clamped in some way and then mechanically twisted about its own axis to form a string of casing which is tied (manually or automatically) and/or alternatively compressed into a mass of tangled casing and then positioned back into the hole of the casing stick by a centrally located push rod. With reference to this prior art, wherein reference is made to the knot located at the extreme end of the shirred casing as the extreme end closure and the method of achieving the end closure, it is worth mentioning, by reference to document No. ep-0294180-a1, that the description of the machine for achieving simple knots reflects the complexity of the tool and lets one understand the cost of this development and the increase of the operating cost for transforming the reformed shirred strand portion into the knotted state, since the operation in the off-line state also requires a lot of machinery of this type, extra manpower, a lot of working area, specialists, maintenance of the machinery, and it is therefore evident that the operation is subject to the risk of accidental machine damage, resulting in operational stoppage and reduced efficiency. The positive side of knotting is that the following advantages are provided: unlike what occurs with other methods, it has the desirable aspect that it can be accepted as part of the first filled sausage.

Another type of closing operation consists in applying some foreign elements with respect to the natural casing material, which perform a fastening action by tightening the end portion of the casing, which casing has been previously shrunk by compressing and/or twisting said end portion. Some of these elements may be, for example, fiber ropes made of natural or plastic fibers, plastic straps, and metal or plastic clips.

It is known that during the filling process, metal clips are applied to close one or both ends of the wrapped sausage (see document No. gb-719317-a). The system is based on a tightening force exerted by an annularly open wire which is strongly closed in a helical manner for clamping, whereby a length of casing is twisted. The toughness of the wire prevents it from opening itself, so that the closure is always strongly fastened. On the other hand, the use of metal clips, rivets or wires extends only to casings which are unintentionally shirred, and not to casings which are to be applied in the particular form of meat filling. Closing elements of this type are those food casings which have a stronger film structure than that of edible collagen and which are not damaged when clamped by wire loops, for example those casings made of reinforced cellulose, non-edible collagen and/or plastic or the like, which usually have a larger caliber (calibre) than casings made of edible collagen intended for use in, for example, vienna sausages, german sausages and the like. An example can be found in document No. gb-1062010-a, in which the closure is realized by: among other things, documents nos. gb-1180067-a and DE-10305580-a1, which form a plurality of longitudinally extending pleats, compress the pleated portions, form holes (eyelets) in said pleated portions, and insert and form riveting means and position the casing hooks adjacent to said holes, also relate to metal clips.

Considering the commonly implemented control protocol for the quality control of those retrofits of shirred casings made of any of cellulose, collagen or plastic, in which, among other things, the strand portions or rods of the finished shirred casing in boxes are subject to comprehensive control, it would be faced with serious drawbacks if each rod carries a metal clip or wire contained therein. The metal closure can also crack the inside of the bad box due to moisture contained in such metal closure and the resulting spoilage of the casing stick.

Some authors have proposed plastic clips as fastening elements which overcome this apparent drawback (see for example document No. wo-9505320-a 1). In this particular case, the plastic clip is constructed of two elements connected by a film hinge, which can be inserted one locked inside the other's end opposite the hinge, so as to firmly grip the twisted one endmost portion of the shirred casing in the middle. Such a clip or fastening element is performed in a similar manner to a strap in the sense that one part has an arm-like coupling section with triangular teeth inclined in one direction, while the other part has a groove of a flexible claw which rides on the inclined surfaces of these teeth when the arm is inserted. The jaws weld the back sides of the teeth to stop the movement of the arms in such a way that the clip is still locked once closed. However, the size, hardness and irregular shape of this element can be conflicting when expelled from the hole outwardly by the meat stuffing pressure, as it can rub against and break the internal folds of the casing, and as such, it can be thrown off in a non-centered direction catching the braking ring of the stuffing corner, thereby breaking the casing, spilling the meat emulsion, and causing spoilage of the running batch.

The ability of this type of fastening element to adhere to the surface of the casing in the molten state may therefore be another important advantage of functioning properly in some embodiments of the closure, to prevent accidental slipping of the tightening element on the enclosed surface, which could lead to the closure being opened when the casing is pushed by meat emulsion during filling.

In any case, the unusual elements present in sausages are not well visible to customers and health authorities, since there is a risk of the object being phagocytosed or transferring undesirable or harmful chemical molecules or substances, such as plasticizers, into the sausage. It is therefore also interesting for the fastening element made of plastic to be simultaneously also water-soluble, in order to disappear, for example, before the sausages enter the market.

Unfortunately, there are no artificial materials available that are both plastic and edible, soluble in water, or capable of adhering to a hydrated surface when the plastic is in a molten state. The collagen matrix of the collagen intestine is in a hydrated state during the pleating operation and its moisture content can vary from 12% up to 30%, once it is stabilized by moisture, even if the average range is between 17% and 24%, on the other hand, moisture content higher than 24% can destabilize the membrane structure, since the collagen membrane tends to be more brittle when the moisture content is lower than 17% and easily breaks when knotted.

Disadvantages of artificial thermoplastic materials have already been discussed. If we sought natural thermoplastic polymers, we could find that many compositions of resins derived from polymeric substances of natural polymers, primarily proteins and polysaccharides or mixtures thereof, could be molded by thermoplastic processes. However, we have found that there are several difficulties or impracticalities in applying these materials in our casing closures; among these, thermoplastic materials are protein-based, so they also require high melting temperatures and high pressures to be processed (thermoplastic extruders) or they are not able to adhere to hydrated surfaces (sometimes due to their high water content). In the case of collagen or other proteins, for example of vegetable origin (soy, gluten, etc.), applied to compositions with other plasticizers in place of water (for example glycerol), the thermosetting behaviour of the compositions is obtained (cf. US-8153176), although the result would be excellent mechanical properties, and therefore they cannot be used as hot-melt plastics. Some other examples of claimed food grade hot melt materials based on polysaccharides, plasticizers and reinforcing agents (edible hot melt compositions) can be found for example in document No. us-6846502-B1; and JP-57158276 discloses a hot melt adhesive composition made of edible ethylene vinyl acetate, a tackifying resin and paraffin wax. All of those are ineffective at bonding to hydrated surfaces.

Other examples of useful resin compositions are those used to make capsules intended for pharmaceutical packaging shells. These capsules contain dry or liquid pharmaceutical ingredients that, once phagocytosed, dissolve in the digestive tract and then release the active agent.

The ingredients of the proteins from which those capsules are made are mainly based on denatured collagen or its hydrolyzed derivatives such as gelatin.

Gelatin is a protein product obtained from the acidic or basic hydrolysis of collagen, which loses its original natural triple helical structure, resulting in a random distribution of shorter segments of the polypeptide backbone, also known as the alpha chain of amino acids, and has an average molecular weight of less than 500 kilodaltons. Thus, gelatin does not constitute a true solution; but rather a colloidal solution or sol is formed. Upon cooling, the sol transforms into a gel, and upon warming, it reverts back to a sol. During the gelling process, the gelatin molecules form a solid three-dimensional structure. Moisture is held between the molecules, and those molecules below a certain temperature are connected to each other by various physical bonds, mainly hydrogen bonds that create a three-dimensional polymeric network. However, the water can circulate and, for example, can evaporate. The infinitely reversible gelation process is by far the most important technical property of gelatin. An analytical measure of the gelling force is called the bloom value. High bloom gelatin is characterized by a high melting point and gel point and a short gel time in the final product. Commercial gelatin types have bloom values in the range of 50-300 bloom. A range of 50 to 100 grams is designated as low bloom, a range of 100 to 200 grams is medium bloom, and a range of 200 to 300 grams is high bloom.

The molecular weight distribution of gelatin is determined by the type and intensity of the hydrolysis method used. In the case of high bloom gelatin under alkaline conditions (called type B), the main part of the molecular mass fraction is in the region of 100000g/mol, corresponding to the alpha chain in question, whereas gelatin under acidic conditions has a much broader distribution. The molecular fraction in the region of 100000g/mol has a higher influence on the gel strength, while the viscosity is mainly a function of the molecular fraction in the molecular weight range above 200000g/mol to 400000 g/mol.

By way of example, mention may be made of the compositions disclosed in patent documents Nos. US-4576284-A (-284A) and US-4591475-A (-475A), wherein said compositions are based on low-grade gelatin. In 284A is disclosed a gelatinous material based on 150 bloom type B gelatin having a water content of 5% to 30%, which acts as a plasticizer. It is mentioned that if a softer product is desired, some edible plasticizer such as glycerol, sorbitol, propylene glycol, etc. may be incorporated into the composition during the process, wherein the edible plasticizer is incorporated in an amount ranging from 0.5% to 40% by weight of the polymer on a weight basis.

In addition to plasticizers, the addition of lubricants, colorants and other polymeric substances for gelatin expansion (known as extenders), such as other protein or polysaccharide gums, is disclosed in the literature (-475A). Some crosslinking agents are also included. Document US-4655840 relates to compositions for injection moulding which are generally hydrophilic, although preferably made of different grades of gelatin, but which can be modified by the addition of other natural hydrophilic polymers, mainly extracted from plants.

Unfortunately, resins based on e.g. gelatin containing hydrogel systems lack sufficient adhesion to hydrated surfaces such as collagen and also lack sufficient adhesion in the molten state to perform correctly in a fast and efficient operation like the one described in the present invention. There is no description made about the mechanical properties of such a resin material, nor about its properties as a binder in a solid state as well as in a molten state.

The polysaccharide compositions, which are also used for capsules, are based on thermoplastic derivatives of cellulose and starch as the main sources, but also from other natural polysaccharides and their synthetic derivatives. Both polymers are generally hydrophilic. Thermoplastic compositions based entirely on polysaccharides such as HPMC or HPC, intended for injection moulding of capsules, are described by way of example in US-4738817 and MX-2010013731-A, respectively.

On the other hand, the said protein thermoplastics used for the manufacture of pet toys, due to their excessive rigidity, have elastic moduli far deviating from the requirements of the present invention, as in the case described in document No. us-6379725, in which a mixture of proteins of vegetable and animal origin, together with plasticizers and additives, is extruded so as to obtain a gelatinous mass having, once cooled, a modulus between 900MPa and 4000MPa and a tensile strength between 20MPa and 40 MPa. It must also be emphasized that this composition is insoluble in water. Another proteinaceous thermoplastic composition based on collagen and water, which can be used for the manufacture of animal consumer products, is described in International application No. WO-2007104322-A1, in which case, however, the polymer is a partially denatured collagen, which has a solubility of at least 25% in water at 60 ℃, and whose extruded product has an elongation of 200% and a tensile strength of about 20 MPa.

The most serious drawback of all the described compositions of natural polymers is the difficulty in finding a single resin capable of achieving the desired combination of physical, or mechanical, thermal, adhesive, and even rheological properties in order to perform correctly both in the closing application and later as an effective tightening element of the closure, and at the same time be edible and water-soluble. Resins based on natural polymers generally achieve an elevated melting temperature, which is rare or without adhesive capacity on wet surfaces, such as collagen films with a water content of more than 15%, (i.e. as is the case with edible and shirred collagen casings) also without sufficient cohesive strength for achieving a fast weld on themselves.

International application No. WO-2009045824-a2 is referred to herein by reference to the tack properties. Some of the mixtures of this document comprise gelatin and glycerol or fructose, which when wetted in the solid state reach a certain degree of viscosity. This has been suggested for use in products such as surgical reinforcement materials to function in conjunction with surgical staplers, where the ratio of dry weight of the polypeptide substance used, such as gelatin, to the polyhydroxy material, such as glycerol, is indicated to be in the range of 30:70 to 70: 30. When wetted in the solid state, becomes an adhesive, for example, on the ECM (outer collagen matrix material). However, this property has no practical effect that can be applied in the closure of the invention, since the collagen casing has whatever water content it has in itself

(at least in the hydration range of interest in the present invention) does not wet the current closure elements, thereby rendering the material of the present invention non-tacky in the solid state.

Disclosure of Invention

A first aspect of the present invention is directed to a closure that satisfies all the requirements set out above, as will become apparent from the following description, regarding its main features and the examples shown below. Such a closure is achieved by using a non-invasive tightening element based on a thermoplastic and edible material, which fastens and/or adheres to a very short portion of casing previously crimped and/or subsequently twisted by a shutter device, wherein said element preferably has the same properties as the casing material itself and is even edible and soluble in warm water, so as to be considered safe when engulfed even if it disappears after processing or cooking the sausage.

As far as the shape and dimensions of this element are concerned, it should preferably be so small as to be contained once it forms part of the closure, and to fit inside the hole of the stick of shirred casing in a perfectly centred position by applying gentle forces; the element should also have a plane of symmetry of radial cross section in order to facilitate its venting outside the hole when subjected to the impact of the meat without the risk of rubbing against the internal folds of the bar and also avoiding hitting the braking ring of the filling machine.

In this sequence of steps which can be converted into an automated system which is as simple as possible, such an element will also have some effect in facilitating its application on a section of casing which has been twisted. Among these features are suitable physical and mechanical properties such as low melting temperature, increased adhesion in the liquid state, and rapid welding properties.

The performance of the fastening element of the closure of the invention can be produced by two complementary forms of action:

a) by tightening only sections of the casing that have been collapsed, which require special physical properties with respect to flexibility and toughness (high modulus), the system is based on the tightening force exerted by the closed and welded-in gripping ring-shaped elements, strongly tightening a section of casing and thereby avoiding slippage of the ring due to pressure.

b) By adhering to the surface of the segment, a possible slipping-off of the ring element is avoided.

The ability of this type of fastening element to adhere to the surface of the casing in the molten state is therefore another important advantage for functioning correctly in some embodiments of the closure, since accidental sliding of the fastening element on the surface it surrounds will cause the closure to open when the casing is pushed by the meat emulsion during filling. However, it must be emphasized that the adhesive capacity and the fastening capacity have a complementary effect in the closure according to the invention, although their respective importance varies depending on the kind of casing and its caliber. It may be the case that small calibers can be kept firmly closed by tightening of the ring-like element of the invention, which has a weak adhesion level on the hydrated surface but a modulus high enough to apply a strong tightening pressure onto the surrounded strand portion of the casing being twisted to avoid further slipping.

We have surprisingly found that a closure element capable of satisfying all the above requirements can be a ring-like tightening element, implemented as a thermoplastic material and made substantially of dry gelatin and anhydrous glycerin, provided that water represents not more than 15% of the total weight fraction of the composition. This thermoplastic material can be welded at low temperatures and has mechanical properties intermediate between viscoelastic and plastic behaviour which enable it to exert a sufficient tightening action to withstand the sausage filling process and at the same time it is edible and water-soluble.

Yannas and Tobolsky have investigated the viscoelastic behaviour and glass transition of gelatin containing the diluent glycerol in the anhydrous and slightly hydrated state over the entire concentration range (Yannas IV, Tobolsky AV. stress relaxation of aqueous gel rubbers. J. Appl. Polymer Sci 1968; 12(1):1-8), but no data have been reported on systematic studies of the adhesive properties of this composition in the molten state.

Surprisingly, the mixture of dry gelatin and anhydrous glycerol produces a thermoplastic solid acting as a hot-melt material characterized by a very low Tg (glass transition temperature) and a relatively low Tm (melting temperature), which is very welcome for the working conditions required for the closure of the invention, and wherein the transition between the adherent and non-adherent states is demarcated by the transition from the solid to the liquid phase, and wherein the liquid phase has a high cohesion and viscosity, and wherein its transition to the solid phase is carried out rapidly due to the low Tm, which allows the welding of the materials to occur sufficiently rapidly. However, solid resins do not have adhesive forces at ambient temperature.

This particular thermoplastic composition is constituted by commercial dry gelatin directly dissolved in anhydrous glycerol under heating conditions between 90 ℃ and 120 ℃ and can be implemented as a thermoplastic and edible material having the desired thermal, mechanical and adhesive properties, provided that the ratio w/w of the ingredients is preferably in the range 2:1 and 1: 3 and a total water content not exceeding 15% of the total weight of the composition. This material is also water soluble but may be rendered insoluble by reacting it with a cross-linking agent if desired.

The mechanical properties required and desired as outlined for the young's modulus can be adjusted by the ratio of gelatin and glycerol in the composition; in this way, a wide range of plastic behaviour from less flexible or less hard to more flexible or more hard can be obtained within a narrow range of variation of the melting temperature (Tm) and the adhesive force, which is very advantageous from the point of view of the efficiency of the closing process.

Mechanical properties: it is highly dependent on the molecular weight of the polymer and the polymer/glycerol ratio.

The mechanical properties of the annular element are very important, since in its closing operation, in order to allow closure in a non-damaging manner, it must not only have sufficient flexibility, but must also have a suitable elasticity (young's modulus) to be able to withstand the expansion caused by the pressure of the air or meat coming from the inside of the casing during filling and to firmly maintain the tightening of the enclosed casing segments. If the ring yields to the expansion stress like an elastic rubber, the flesh can open its way through the closure and spill out. The higher the modulus, the less elastic the material, and conversely the lower the modulus, the more elastic.

The solid resin has a plastic-like behavior, the properties of which vary under the influence of the molecular weight of the polymer, the bloom value and the proportion of the polymer in the resin composition. The higher the molecular weight and bloom (>150 bloom), the greater the viscosity and hence the cohesive force.

We have found that in order to have the correct properties and to prevent all of the mentioned disadvantages, the ring material must conveniently have a modulus of at least 0.5MPa and preferably no more than 50 MPa. In this sense, the best results can be obtained in combination with a gelatin having a high bloom, conveniently higher than 150 bloom, preferably higher than 200 bloom, since this grade of polymer gives the thermoplastic composition the best cohesion at the temperature of room temperature conditions.

Melting point:

once the heat seal closure is transferred to the machine, both the melting point of the material of the ring and the speed at which the material can produce a weld with itself are critical to the effective performance of the closure; it is also desirable to have a low melting point so as not to affect the integrity of the casing when in contact with the molten material. The lower the temperature involved in this process, the safer and easier it is to use the system.

Yannas and Tobolsky set the melting temperature of the slightly hydrated gelatin at 175 ℃. + -. 10 ℃. It is well known that the solid ingredients in a binary composition of, for example, gelatin and glycerin dissolve in the other ingredients and that the cure point of the composition is lowered by increasing the concentration of the ingredient having the lower cure temperature, which will lower the cure temperature of the mixture.

The melting temperature of the resin composition varies depending on the ratio of the polymer (gelatin/glycerin ratio), and an increase in the ratio of the polymer makes the melting temperature higher. However, a compromise should be reached between the plastic properties, the melting temperature, the adhesion of the resin in this molten state, and the improved adhesion being correspondingly associated with a fast setting time of the fusion of the material. As this ratio increases, the viscosity of the material in the molten state also increases, but the lower the total water content of the composition, the greater the ability of the material to adhere to the wetted surface of the collagen film.

We have found that the optimal temperature range for carrying out the process of ring closure is 40 ℃ to 90 ℃, as such temperatures do not affect the integrity of the collagen casing. We have found that when the polymer/polyol ratio is about 1: 1, and the closer to 1:2 or even higher allows a rapid formation of a weld because within this ratio a large variation in mechanical properties is obtained without a large increase in melting temperature, while the cohesion of the melt is high, allowing a rapid formation of a weld at the instant of contact between the two surfaces, which weld can be produced with a slight decrease in temperature. In this connection, we have also found that the gelatin must preferably have an elevated degree of polymerization, meaning that there must be an elevated bloom, in particular above 150 bloom, and more preferably from about 200 bloom to about 300 bloom.

Binding power:

the faster the weld condenses, the faster the sealing step and the more efficient the sealing system.

The term "cohesion" as used herein refers to the resistance faced by the fluid material to phase separation from itself, and in the case of polymer dispersions of amorphous polymers, it depends directly on the molecular size of the polymer molecules and on the temporary bonds, mainly hydrogen bonds, between these molecules in the polymer matrix.

Water solubility of the locking ring:

another important factor in the matrix resin of the locking ring of the closure of the invention is its water solubility, since the sausage product in the edible collagen casing with the closure of the invention will undergo a cooking process before packaging. The temperature rises above 70 ℃ during normal processing cycles and it may be appropriate that the ring disappears or remains in it during the cycle-for example if the ring is used as some kind of marker. Thus, the solubility of the resin material of each composition under normal processing conditions is also reflected in table 1:

the pressure ring was soluble in hot water and was able to dissolve completely in water at 81.5 ℃ over a 35 minute period. If the ring is required to last longer, gelatin may be replaced by partially denatured collagen as used in international application No. wo-207104322-a1, or some cross-linking agent capable of insolubilizing the polymer by creating covalent bonds may also be used, as is well known in the art. Such crosslinking agents are preferably food grade crosslinking agents in very precise amounts like aldehydes.

And (3) parameter measurement:

tensile properties of the plastic:

the tensile tests were carried out according to ISO 527-2:2012/5A/50 at a test speed of 50mm/min in a universal drawing machine (at least type 1 according to ISO 7500-1 and ISO 9513) equipped with a contact extensometer (at least type 1 according to ISO 9513) coded MO 0217-2 and a self-clinching pliers (at least type 1 according to ISO 7500-1 and ISO 9513) coded ZWICKMO 02/17. We use a grip distance of 50 mm. A type 5A sample was obtained by punching. Prior to testing, samples were conditioned for 16 hours at 23 + -2 deg.C and 50 + -10% RH, and in the laboratory at 23 + -2 deg.C and 50 + -10% RH.

Melt index:

for measuring the viscosity of the molten thermoplastic; this parameter is selected to evaluate the change in adhesion of the thermoplastic composition as a function of temperature. The test was performed with a flow meter encoded as MO 02/16 as shown in UNE EN ISO 1133-1: 2012. We used nozzles with a length of 0.025. + -. 8.000mm and a diameter of 2.095. + -. 0.005 mm. The distance of travel of the piston was 30 mm. The premelting time was 5 minutes. The test conditions were: a) temperatures 120, 100, and 80; b) for sample 1:2 were loaded with 1.2, 5.0 and 21.6. No cutting time was used.

Determination of thermal transition by Differential Scanning Calorimetry (DSC):

the measurement was carried out according to ISO 11357:1997 on a calorimeter coded as Pyrs Diamond MO 01/21, produced by Perkin-Elmer company, in an aluminum crucible and under a nitrogen stream, using 5 to 10mg of a representative sample. Indium and zinc were used for the standard mode. Results were averaged over two determinations. The determined value is used for the second scan. The test parameters are: a) initial temperature-60; b) the final temperature was 150 ℃; c) heating speed is 20/min; d) the cooling rate was 20/min.

Adhesion:

the adhesion was tested on pieces of flattened casing equilibrated at 85% RH in a climatic chamber until the casing achieved moisture levels of 12%, 21% and 35%. The various resins were melted in a steel plate and cast onto an extended casing sheet which expanded the preformed films thereon in the molten state to approximately 3cm wide and 10cm long each. These resins were allowed to cool for 5 minutes and then the peel strength was measured with a force gauge at 90 ℃.

Tack at room temperature is judged by the tackiness of the adhesive to a human finger.

Residual moisture:

in the preparation of the compositionThe apparent water content was determined by testing after drying gelatin powder in an oven at 105 ℃ for 24 hours at atmospheric pressure. The data obtained provide the basis for calculating the residual water content in a binary composition formed from commercial gelatin and glycerin. However, when a change (decrease) in the residual amount in the composition is concerned, 10 in the oven^-3The drying treatment is performed at a vacuum pressure of mm hg and a temperature of 25 to 105 c. This calculation is performed by taking the weight of the sample under test.

Drawings

For the purpose of supplementing the description made and of facilitating a better understanding of the characteristics of the invention according to its preferred practical and exemplary embodiments, a set of drawings is attached as an integral part of said description, the following figures being shown in an illustrative and non-limiting nature:

fig. 1 shows a plurality of hollow worm-like rods with longitudinal V-shaped openings molded by injection molding.

Fig. 2 shows how a worm with a longitudinal groove having a V-shaped cross-section reaching the axial hole is moulded so that any section cut transversely from the worm has an annular opening in the form of a "c". Fig. 2 shows a tightening element which is a solid ring-like element made of an edible and water-soluble thermoplastic composition with a smoothly curved V-shaped entrance gap leading to a central hollow (holow), while fig. 2b shows another embodiment, in which the ring-like element is composed of a proportional gelatin/glycerin which allows the ring to exert a strong tightening effect on the twisted portion of the casing, while the same composition material has a sufficient elastic behavior to allow the ring to be opened without breaking in a short time maintaining the fit of the twisted string of casing.

Fig. 3 shows three diagrams, wherein: figure 3a shows the end of the shirred sausage-casing strand portion captured by a pincer at the end of a rod whose axis coincides with the axis of the strand portion. The rod retracts and pulls the strand portion such that the uncrimped length of casing does not exceed 5 cm. At a point between the junction of the shutter member with the tucking section (approximately 10mm of casing) and the point of grasping the pliers, the shutter member (electrically variable aperture) rapidly closes its blades and collapses the un-tucked casing as shown in fig. 3 b. Furthermore, while closing the shutter member, the nipper rod is rotated on its axis and twists the remaining casing section, thereby producing a string (bunch) about 3cm long in the axial direction of the strand of shirred casing, as shown in fig. 3 c.

Figure 4 shows the split ring closed by the travelling clamp to produce the thermoplastic material in the form of a ring.

Fig. 5 shows a detailed view of fig. 3 a.

Fig. 6-9 show sequential perspective views of the process of the present invention.

Figure 10 shows the bar of casing finally obtained.

Detailed Description

Preferred embodiments of the closure.

In a preferred and simplest embodiment, the closure of the invention consists of a short section of casing which has been twisted and is clamped by a tightening element. The tightening element is a solid annular element made of an edible and water-soluble thermoplastic composition, having a smoothly curved V-shaped entrance gap leading to a central hollow portion (see fig. 2a), wherein the previously tightened and/or twisted portion of the casing will be positioned by pushing it with a wedge.

The loop can be manufactured by any method known in the art of plastic forming and it can be welded (as shown in fig. 1) with a number of repeating elements (loops) interconnected by weak seams in the strand part or bar, like staples of a stapler, to facilitate the machinability of the feeding process of the loop unit and in this way all loops are open before being used alone.

Thermoplastic composition

Current thermoplastic compositions include dry gelatin, anhydrous glycerin and water. The water content does not correspond to the residual water amount remaining after drying of commercial gelatin (the initial water content of which typically varies between 10% and 13%), and it is practically unusable but only to avoid cross-linking of the gelatin. The water content of the composition will be less than 15%, preferably between 1% and 10%, and most preferably between 2% and 3%.

According to all what has been exposed above, the most suitable gelatin is one of the food grade gelatins higher than 150 bloom, preferably between 200 and 300 bloom; this grade of gelatin provides higher adhesion to the resulting resin because of the relatively large molecular weight distribution. One example of a commercial gelatin having related characteristics is one of type a or type B from gelata AG (f.e. gelata hedgel, g.rxl, g.advanced, g.pa, etc.) in germany, wherein the characteristics of the commercial gelatin include: 8-30 mesh, 200-300 bloom, 25-55 viscosity and 8.5-12.0% water content; another is Junc Gelatine (Mikel Junc Gelatines, class leice, heroin) in the same characteristic range and with a water content of 10.5%, which is used in the examples below. The reduction of the water content in the composition will be achieved by further drying in an oven.

Preparation of rods of connected rings

The composition can be homogenized by well known methods in a single screw extruder such as Rheomex 302 or a co-rotating twin screw extruder such as Krupp Werner & Pfleiderer ZSK25, the pressure inside the co-rotating twin screw extruder increases and the shear force on the mixture acting as it travels through the interior increases while the temperature is greatly increased above the melting temperature of the gel-like composition. As is well known to those skilled in the art, this process is suitable for regulating the temperature increase by controlled cooling of the extruder barrel. The internal temperature can vary between 80 and 120 ℃. During the plastification process, the pressure inside the extruder is generally low relative to the pressure in the next injection molding step. The pressure during mass plasticization is generally between 20bar and 75bar, depending on the polymer/polyol ratio in the composition. The plasticized resin can be injection molded directly or preferably in a next step by conventional processes into one or more cavities of a mold. Once the plasticizing step has been completed, the mass will be extruded through a die fitted with regular circular holes into endless strand portions each having a diameter of 2mm to 4 mm. The strand was then partially cooled and pelletized in a conventional pelletizer. The granules are transferred to the next injection moulding operation, in which the pressure inside the extruder is increased up to 70 to 120bar, and finally from there a solid body with a connected ring in the shape of a rod or worm screw is obtained, which can be ejected from the mould when the mould is opened after cooling is completed.

Needless to say, the injection moulding operation can be used not only for making worm-like continuous rings, but also for making single rings, however, the choice should depend on how the closure machine is designed for its optimum performance.

To modify (reduce) the residual moisture content of the molded solid body, the process will be carried out in an oven at 10^-3Vacuum pressure of mm Hg, temperature of 25 to 105 deg.C. The calculation of hydration level was performed by taking the weight of the sample before and after the drying process and assuming that the initial moisture content was derived from official specifications for the raw material.

Depending on the diameter of the hole of the shirred strand portion of the casing, the worm may have a length of a few centimeters and an outer diameter of 6 to 8 millimeters. The diameter of the longitudinal bore (axial bore) of the worm-like element is in the range of 1 to 4mm, which also depends on the thickness of the twisted string of casing to be enclosed. The worm is molded with a longitudinal groove in a V-shape in cross-section that reaches the axial bore so that any segment cut transversely from the worm has an annular opening in the form of a "c", as shown in fig. 2. The opening (1) (gap) is the path through which the crimped section of the twisted cord fits into the hollow portion of the ring of the fastener.

Ring (C)

A tightening element or ring of the invention can be cut from a molded worm-shaped preform (fig. 1), instead of being manufactured individually, by cutting it in cross-section, which will enable a plurality of rings to be obtained. The worm-like preform is caused to have a segmented appearance by the necking portions arranged in a uniform order, thereby giving it a ring-like appearance.

A ring composed of a thermoplastic composition of edible resin based on gelatin can exhibit the following basic characteristics once placed around a shrunken casing segment:

a) sufficiently adheres to the contact surface in the molten state, even in the wet state, to ensure the fastening of the element to the casing material and thus prevent the element from slipping away from the material,

b) has a sufficient modulus of elasticity (even without too much toughness) to apply sufficient radial tightening tension to the twisted/pinched portion of the casing to which it is fastened, and

c) is safe, edible and water-soluble.

In a preferred embodiment, the annular element is constituted by a proportional gelatin/glycerol which gives the composition a modulus higher than 10MPa and more preferably higher than 20MPa, which is sufficiently elevated to allow the ring to exert a strong tightening action to the twisted portion of the casing, while the same composition material has a sufficient elastic behavior to allow the ring to be opened without breaking within a short time of maintaining the fit of a string of casings (see fig. 2 b).

In another preferred embodiment, the tightening element is a solid annular element similar to the tightening elements described above, which is opened before being placed around the pre-tightened part of the casing (see fig. 2a), then closed and heat sealed in order to maintain a firm tightening on the casing material. All of this is possible because the thermoplastic composition from which the ring is made is capable of welding to itself by low temperature heating and by having the characteristic of rapid weld solidification.

The opening (1) of the c-shaped ring is a path via which the ring can be fitted on a crimped and/or twisted section of the casing, in other words via which the casing section enters the ring towards the centre of the ring. Once the piece of casing is fitted over the central hollow part of the ring, the opening (1) is mechanically closed. The closing operation itself comprises heat sealing the now joined ends of the c-shape and welding the rings on the enclosed section of casing.

As the split ring made of thermoplastic material is closed by the mobile pliers (fig. 4) to create the annular form, the two opposite parts of the opening are previously melted by contact with the metallic wedge element heated at a suitable temperature, so as to melt at least at one contact surface; the two surfaces are then brought together until they are in contact, at which point it is important that, in addition to the pressure exerted by the jaws forcing them closed, the slight reduction in the initial contact temperature also promotes a rapid increase in the adhesive force of this fusion of the material to be solidified, which adhesive force, before complete curing, is already large enough to prevent the ring from opening (fusion setting) and to avoid premature loosening of the grip once the jaws release the ring just formed.

Procedure for sealing operation

The closing operation is a cycle carried out as follows:

a) one end of the shirred sausage-casing strand portion is caught by a pincer (fig. 3a, not shown) located at the end of a rod whose axis coincides with the axis of the strand portion. The rod retracts and pulls the strand portion such that the uncrimped length of casing does not exceed 5 cm. At a point between the junction of the shutter member with the pleated section (approximately 10mm of casing) and the point of grasping the pliers, the shutter member (electrically variable aperture) rapidly closes its blades and collapses the un-pleated casing (fig. 3 b).

b) While closing the shutter piece, the nipper rod is rotated on its axis and twists the remaining casing section, producing a string (bunch) about 3cm long in the axial direction of the shirred thigh portion of the casing (fig. 3 c).

c) The opened c-lock ring is moved up under the newly formed string of casing. The loop is clamped inside the open mouth of the clamp by means of a clamp of the open-ended type, which acts as a closure of the loop while cutting the string. The ring is moved upwardly to fit a string of casing inside its axial hollow, with the opening of the ring in the form of an upwardly facing "V". The clip stops rising just when the axis of the loop coincides with the axis of the string.

d) Simultaneously with the raising of the locking ring, the pusher is lowered to push a string of casings within the hollow of the ring (fig. 7). The ends of the rods are made of steel, have flat wedges and straight edges on the ends and are kept preheated to a temperature sufficient to melt the resin ring. The axis of the rod coincides with both the direction and the axis of the ring elevation. While the cord is fitted into the axial bore of the ring, the pushrod contacts and melts a layer of the opposing surfaces to be joined, at least by one side, but preferably by both sides, thereby sealing the ring;

e) while the plunger is removed again, the gripper (fig. 8) carrying the loop closes, causing on the one hand the fusing together of the contact surfaces on the twisted sausage casing rope, while on the other hand the cutting off of the excess end of the sausage casing. The clamp exerts a moderate and continuous force on the ring for a predetermined time, which may vary from 2 to 5 seconds. After this welding time, the clamp opens and descends to its rest position, where it is loaded into the next clamping ring.

f) The shutter member opens rapidly. The ring is closed and the weld also acts on the body (gut) section embedded therein and in a further optional step.

g) The closure is pushed inside (hole) of the shirred stick of casing.

Other variants of the invention

It is envisaged that also in the present invention, the casing may be turned inside out after the closing operation has been performed, or the closure may be introduced into the lumen of the stick so that the annular closure is located within the internal bore of the stick (as shown in figure 13 of EP-2266410, the ring should encircle the point marked 14). After filling, the closure of the invention can remain in the outer surface of the sausage or in the surface that contacts the sausage. In this case, some closures can remain after cooking, which should not be a problem as edible closures.

The rings of the present invention may have other forms such as hexagonal, etc., and need not be circular. Also, the ring need not be edible (applicable to other casings) nor water soluble.

Example (c):

example I: preparation of samples of the different compositions.

For an embodiment of the composition, a dry powder of food grade gelatin of 240 to 260 bloom of Junc m. (heroin, spain) is used, having an average particle size (0.3 to 0.8mm corresponding to 20-50 mesh, in this case in particular 35 mesh), with an apparent water content of 13%. To obtain compositions with an increased gel/glycine ratio of between 2:1 and 1:2.5, 100 parts of commercial gelatin with a residual moisture content of 13% were taken in each case and combined with the appropriate parts of anhydrous glycerol to give compositions with different apparent moisture contents, as shown in the following table:

between gel/glycerol in such a way as to obtain a composition with an increased ratio of 2:1 and 1:2.5 100 parts of commercial gelatin taken in each case with a residual water content of 13%, combined with the appropriate fraction in anhydrous glycerol, the resulting composition is shown in the following table with the various contents in apparent moisture:

the polyol was food grade anhydrous glycerol from Sigma-Aldrich. The composition is prepared by dissolving gelatin directly in commercial glycerin with vigorous stirring at temperatures varying between 80 and 120 ℃. The resulting ratios expressed in table X refer to the weight ratio of the anhydrous pure product.

Table I:

example II: determination of the melting temperature:

from the samples prepared in example I in different compositional ratios, the thermal transition was determined by a technique of Differential Scanning Calorimetry (DSC). The average results are listed in the following table:

table II:

tg ═ glass transition temperature; tm is the melting temperature.

Example III: and (4) determining the rheological coefficient.

Table III:

MVR means melt volume ratio.

A sharp decrease in fluidity (and thus an increase in viscosity and therefore in cohesion) due to a change in the ratio of both gelatin and glycerol is clearly seen, reducing the applicable temperature. This gives the idea of: the fastener ring closure of the present invention is most suitable in terms of the combination of optimum welding performance and quick fixing of the weld when performed at relatively low ambient temperatures.

Example IV: determination of the modulus of elasticity

The tensile properties of the various specimens from example I were calculated based on the general principles of ISO527-1 for the dog bone specimen by ASTM method D638-10 (equivalent to ISO527-2) which specifies the test conditions for determining the tensile properties of molded and extruded plastics. The test was performed using dog bone samples. The results are shown in Table IV.

Table IV:

a sharp increase in the modulus of elasticity between the transition of the ratio 1 to 2 can be observed in the table. Example V: determination of adhesion

Adhesion was tested on various samples made from all samples according to example I. In addition to this, the content of the composition polymer/diluent (gelatin/glycerol) amounts to a ratio of 2:1 and the composition with a residual moisture content of 9% was oven at 60 ℃ and Hg10^-3Drying was carried out under conditions of vacuum pressure of mm hg until moisture contents of 6%, 3%, 1.5% and 0.5% respectively (corresponding to samples a7 to a10, respectively) were reached.

Table V: adhesion of resins of different compositions and water content on collagen casings with moisture contents of 12%, 21% and 35% (based on the total weight of the casing).

It is also pointed out that compositions with very low water content have an intrinsic adhesion increase once they are melted, in particular the amount of polymer in the resin is higher.

Non-peelable means that when a piece of resin film is attempted to be peeled off from the surface of the body to which the resin film is cast by melting, the resin film, once cooled and solidified, is able to pull apart and drag the material from the body without separating from it.

Example VI: a rod of sealing/fastening ring made of gelatin and glycerin was prepared by injection molding.

As depicted in fig. 1 of the drawings, a plurality of hollow worm-like rods having longitudinal V-shaped openings are molded by injection molding. The starting composition of extruded resin material was formed from 200 bloom of gelatin (Junc), glycerol (food grade glycerol available from Sigma-Aldrich) and residual amounts of water, and the final proportions of the components in the mixture corresponded to samples a4 and A8, respectively. The dimensions of these elements for each composition have on the one hand a length of 20cm, a diameter of 8mm, with a central hollow portion of 2mm in diameter; and on the other hand has a diameter of 12mm, wherein the central hollow portion has a diameter of 4 mm.

The material is plasticized and extruded by means of a single-screw extruder which is widely used in the plastics processing industry, with process conditions of a temperature in the range from 87 ℃ to 104 ℃ and a pressure in the range from about 50 to 100 bar. The plasticized material was extruded through a circular cross-section die with six holes each 2mm in diameter. The cooled down endless strand part is then granulated in a conventional granulator. The pellets are used to make worm-like rods on conventional injection molding machines. The material was injected into the stainless steel mold at a pressure in the range of 1000-. The stick is placed on a stand and set dry until its moisture content is 2% to 3%. The resulting bar is flexible and strong.

A plurality of short segments of 8mm are obtained by cutting the bar in a transverse manner with a cutting tool. The cross-section of each segment has the shape of a split ring or C-ring. The opening of such a C-shaped ring is the path through which the collapsed and/or twisted casing segments are inserted into the ring.

Example VII: embodiments of a closure portion; filling test of the closed casing and cooking test of the resulting sausage with its closure.

To test the performance of the closure, two sizes of edible collagen casings were selected; i.e. a caliber 21, in which small rings (diameter 8mm) made of compositions named a2, a4 and A8 were applied; and a bore 28, in which rings of 12mmd diameter made of the same composition are applied.

In each case where the pleated bar was manually sealed, the following were: one rod is advanced to shirr approximately two inches of casing and then the unrolled casing is collapsed within one inch of the first shirred rod using a manual shutter. The remainder of the casing, once gripped by the shutter blades, was twisted to form a string of approximately two millimeters in diameter for a casing of diameter 21 and a string of approximately four millimeters in diameter for a casing of diameter 28.

Table VI: resistance of the closure to the filling process

By selecting the dimensions as indicated, the annular closure made of the respective composition is directly applied. Each composition and half of the rings of each diameter were sealed in a manner as described in memory (memory) by heating to 85 ℃ using a heater with a trapezoidal head for tin plating. The heater is first used to push the string of casing into the central bore of the ring; once mated, the sides of the heater contact the contact surfaces of the rings, resulting in rapid melting of the surface layer; the heater is then subsequently removed, which process takes place simultaneously with the closing of the ring. Once the melted faces of the rings are brought into contact with each other, removal of the closing pressure within 2 seconds enables a weld to be formed with sufficient adhesion. After the pressure on the ring is removed, the ring remains closed, forming a cinch ring. The other half of the ring is not welded but is simply pressed after fitting the casing into its central hole.

The shirred and sealed sausage casing sticks were filled with sausage meat stuffing on a RobbyVemag model 2 machine at a rate of 80 parts per minute by using the brake control of the filling machine.

The results of the filling process are listed in table VI. As reflected in the results, those rings made of composition a2 and not sealed were relatively able to withstand the filling process, making the larger rings more resistant to opening, depending on their diameter, depending on the respective pipe diameter to which they are applied. In the case of small rings made of composition a2, the addition of their smaller wall thickness to the lower modulus of elasticity also favours the opening of some of them during filling, so that the use of their heat sealing is recommended in these cases.

Subsequently, the sausages were hung on hooks for baking for four hours in a simple cycle at 90 ℃. In all cases, the first sausage, i.e. the carrier of the loop, remains intact as a whole into the beginning of the cooking cycle. During this period of time, the meat mass coagulates and the sausage maintains its shape until the end of the cycle. During this time, the sealing ring of each first sausage gradually dissolves to disappear before the end of the cycle. The end result is satisfactory not only for excellent closure performance, but also because the use of sausages to carry the closure is more realistic than using other parts in the same way.

Claims (18)

1. A tubular casing for food products made of an edible collagen film, the tubular casing having an end closure; the end closure is located at a length of casing, wherein a section of the length of casing is radially compressed towards its axis and/or twisted such that the length of casing acts to block an internal path located within it; and wherein the length of compressed/twisted casing is surrounded, fastened and tightened all the way by a solid annular element, which is welded completely or partially to the surrounded part of the collagen casing, and wherein the ring consists of a thermoplastic material characterized by being edible.

2. A tubular casing as claimed in claim 1 wherein the tubular casing is shirred.

3. A tubular casing according to any of claims 1 and 2, wherein the thermoplastic material of the rings is an edible thermoplastic composition based on proteins, polysaccharides or mixtures thereof.

4. A tubular casing according to any of claims 1-3, wherein the young's modulus of the thermoplastic composition of the closed rings in solid state, measured at 23 ℃ and 50% RH in the ambient condition, is in the range of 0.5MPa to 50 MPa.

5. A tubular casing according to claim 4 wherein the thermoplastic composition of the closed loop has a melting temperature (Tm) of between 40 ℃ and 98 ℃.

6. A tubular casing as claimed in any of claims 1 to 5 wherein the closed loop thermoplastic and edible material is a non-crosslinked and water soluble proteinaceous thermoplastic composition comprising a mixture of dry gelatine and a polyol, and wherein the weight content of water is in the range 0.5% to 15%; preferably between 1% and 5% and most preferably from 2% to 3% of the total weight of the composition.

7. A tubular casing as claimed in claim 6 wherein the thermoplastic and edible material of the closed loop is a cross-linked and water insoluble composition.

8. A tubular casing as claimed in claim 6 or 7 wherein the gelatin has a bloom value of greater than 150.

9. A tubular casing according to any of claims 6 to 8 wherein the polyol is glycerol.

10. A tubular casing according to any of claims 6-9 wherein the young's modulus of the closed loop proteinaceous thermoplastic composition in solid state, measured at ambient conditions of 23 ℃ and 50% RH, is in the range of 0.5MPa to 50 MPa.

11. A tubular casing according to any of claims 6, 8, 9 and 10 wherein the proteinaceous thermoplastic composition of the closed loop has a melting temperature (Tm) of between 40 ℃ and 98 ℃.

12. A tubular casing according to any of claims 1 to 5 wherein the thermoplastic and edible material of the closed loop is a polysaccharide based thermoplastic composition comprising cellulosic fibres including micro and nano fibres mixed with other ingredients selected from the group consisting of starch, methyl cellulose, hydroxymethyl cellulose, hydroxypropyl methyl cellulose and mixtures thereof.

13. A tubular casing as claimed in claim 12 wherein the young's modulus of the closed-loop polysaccharide thermoplastic composition in the solid state measured at ambient conditions of 23 ℃ and 50% RH is in the range 10MPa to 50 MPa.

14. A tubular casing as claimed in claim 13 wherein the polysaccharide thermoplastic composition of the closed loops has a melting temperature (Tm) of between 40 ℃ and 98 ℃.

15. A shirred tubular enteric coated rod made of edible collagen film having an end closure according to any one of claims 1 to 14.

16. A method for obtaining an end closure according to any one of claims 1 to 14, characterized by the steps of:

a) providing a tubular casing which is smooth or shirred in cross-section;

b) providing a batch of molded c-shaped open rings made of the thermoplastic and edible composition according to claims 1 to 12, according to the description and the drawings,

c) gripping and twisting a short final section of casing from step a) to form a short strand portion;

d) pushing the twisted strand portion obtained in step C) through the inlet gap of the ring and inserting into the interior of the C-shaped split ring until the longitudinal axis of the strand portion coincides with the axis of the hollow part of the ring; or alternatively

e) According to step d, pushing the twisted strand part by means of a thrust element on at least one side and inserting the twisted strand part into the hollow part of the ring and applying a heat source until the twisted strand part fits within the hollow part of the ring; then retracting the thrust element and at the same time closing the c-shaped ring firmly until the opposite sides of the two tips come into contact, to weld the contact between the two tips and the contact between the ring and the strand portion of the twisted casing currently wrapped in the ring;

f) maintaining the closing pressure on the ring for 0.5 to 5 seconds and then releasing the closing pressure to release the closure formed thereby;

g) cutting off the remaining end of the strand portion, an

h) The looped end closure is inserted into the hole of the shirred thigh section.

17. The method of claim 16, wherein step (g) is completed simultaneously with step (e).

18. A food product encased in a tubular casing made of an edible collagen film and having an end closure according to any preceding claim.