HK1230871B - End closure for an edible collagen casing and a method for obtaining thereof - Google Patents

Description

End closure for edible collagen sausage casing and method for obtaining the same

Technical Field

The present invention has applications in the meat casing industry, and in particular in the area of shirred casing closure. It aims to simplify the closure of shirred casings without wasting excessive casing material. It ensures that it withstands the powerful impacts of the meat paste during filling, does not invade the interior of the casing tube, and imparts desirable properties to the finished product, allowing the first filled sausages of each batch to be recycled along with the remaining sausages produced. At the same time, and particularly in the edible collagen casing market, its edibility is comparable to that of casings made from natural raw materials. The invention also aims to provide a closure whose production can be easily automated, even in-line on the same machine that shirrs the casings. This is why the material also requires a low melting temperature to prevent damage to the casings and a high adhesive strength for rapid welding to achieve high application efficiency.

Background Art

The preliminary closing of one end of a food casing is an essential step for successful filling during the further filling process. A wide variety of end-closing solutions are used in projects in the food casing industry to complete the manufacture of practically all ready-to-fill food casings. This finishing stage encompasses a wide range of processing operations, often referred to as "reforming", in which the casing, in its flattened form, is unwound from its original coiled state and then shirred or alternatively segmented, coated, tied with rope suspension rings, wrapped with elastic tightening netting, or seamed to produce a longitudinal hem or final seal, etc., in order to finally close it at one end.

For clarity, the following definitions are provided:

The casing is a smooth, flexible, hollow tube formed from a natural or artificial membrane, having a beginning and an end.

A length is a portion of a casing, i.e. a stretch of casing.

A string is a length, part or segment of twisted casings.

The terminal corresponds to the very end of the casing.

The strand is a stick or shirred and compacted casing that forms a round hollow tube.

A bore is the lumen of a hollow tube such as a strand or rod.

Different reforming operations are applied depending on the type and purpose of the casing, but most of them are done by sealing the end of the casing, which is the first part of the sausage to be formed and which will be subject to the first impact 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 transmitted by the entering mass without opening or breaking.

Most sealing solutions aim to create a seal with the casing material itself, without introducing any foreign elements. These sealing processes appear to be simple tasks; however, the machinery used to perform them is actually quite complex. From an engineering and construction perspective, operations that are simple for the human hand become daunting tasks when transferred to a machine.

The end closure formed by the casing material itself usually uses a piece of untucked casing from the end of a strand of shirred casing, which is clamped in some way and then mechanically twisted around its own axis to form a string of casings, which is tied into a knot (manually or automatically) and/or alternatively compressed into a tangled mass and then positioned back into the hole of the casing rod by a central push rod. With reference to this prior art, which relates to the use of a knot at the end of the shirred casing as the end closure and the method for achieving the end closure, it is worth mentioning that the description of the machine for achieving a simple knot in document No. EP-0294180-A1 reveals the complexity of the tool and the cost of this development and the increased operating costs for converting the modified shirred strand into a knotted state. Since the operation in an offline state also requires a large amount of this type of machinery, additional manpower, a large working area, professional personnel, and maintenance of the machinery, it is obvious that this operation is subject to the risk of accidental damage to the machinery, resulting in operational stoppages and reduced efficiency. The positive side of knotting is that it has the advantage that, unlike what is produced by 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 certain elements foreign to the natural casing material, which perform a tightening action by tightening the end portion of the casing, which has been previously collapsed by compression and/or twisting. Some of these elements may be, for example, fiber ropes made of natural or plastic fibers, plastic ties, and metal or plastic clips.

It is well known that metal clamps are used to close one or both ends of wrapped sausages during the filling process (see document No. GB-719317-A). This system is based on the tightening force exerted by a wire with an open loop, which is tightly closed in a spiral to tighten the casing. The toughness of the wire prevents it from opening on its own, thus ensuring that the closure is always firmly secured. On the other hand, the use of metal clamps, rivets, or wires only applies to casings that are not intended to be shirred, and not to casings that are intended for use in special meat filling applications. This type of closure element is intended for food casings that have a membrane structure stronger than that of edible collagen and that is not damaged when clamped by the wire loop, such as those made of reinforced cellulose, non-edible collagen, and/or plastic, which generally have a larger caliber than casings made of edible collagen intended for use in sausages such as Vienna sausages and bratwurst. An example can be found in document No. GB-1062010-A, where the closure is achieved by forming a plurality of longitudinally extending pleats, compressing the pleated portion, forming holes (eyelets) in the pleated portion, and inserting and forming riveting means and positioning casing hooks adjacent to the holes. Documents No. GB-1180067-A and DE-10305580-A1 also relate to metal clips, among others.

Considering the general control protocols commonly implemented for the quality control of those transformation processes of shirred casings made of any of cellulose, collagen or plastic, in which, among other things, boxes of strands or rods of finished shirred casings are subjected to comprehensive control, it would be a serious disadvantage if each rod had a metal clip or wire contained therein. This metal closure could also cause the interior of the bad box to crack due to the moisture contained in it and the resulting spoilage of the casing rod.

Some authors have proposed plastic clips as fastening elements that could overcome this apparent disadvantage (see, for example, document No. WO-9505320-A1). In this particular case, the plastic clip consists of two elements connected by a film hinge, which can be inserted so that one locks inside the other at the end opposite the hinge, thereby firmly clamping the twisted end portion of the shirred casing in the middle. One part of this clip or fastening element has an arm-like coupling section with triangular teeth inclined in one direction, while the other part has grooves with flexible claws that ride on the inclined surfaces of these teeth when the arms are inserted, in this way performing similarly to a drawstring. The claws weld to the back of the teeth to stop the movement of the arms, so that once closed, the clip remains locked. However, the size, hardness and irregular shape of this element can be counterproductive when it is expelled from the orifice by the filling pressure, as it can rub against the internal folds of the casing and break it, and likewise it can be thrown in an off-center direction and catch on the stop ring of the filling corner, thereby breaking the casing, spilling the meat mixture and causing spoilage of the batch in progress.

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

In any case, the presence of unusual elements in sausages is not easily visible to consumers and health authorities, as there is a risk that the object could be swallowed or transfer undesirable or harmful chemical molecules or substances, such as plasticizers, into the sausages. It is therefore also interesting that the fastening element, made of plastic, is also water-soluble, so that it disappears before the sausages reach the market, for example.

Unfortunately, there are no available artificial materials that are both edible, soluble in water, or capable of adhering to hydrated surfaces when molten. The collagen matrix of collagen sausage is hydrated during the shirring operation, and its moisture content can range from 12% to 30%. Once its moisture content stabilizes, even though the average range is between 17% and 24%, moisture contents above 24% can destabilize the membrane structure, as collagen membranes below 17% tend to be more brittle and easily broken when used to tie knots.

The disadvantages of artificial thermoplastic materials have already been discussed. If we look for natural thermoplastic polymers, we can find many compositions of resins derived from polymeric substances of natural polymers - mainly proteins and polysaccharides or mixtures thereof - that can be molded by thermoplastic processes. However, we have found that the application of these materials in our casing closures presents several difficulties or impracticalities; among them, thermoplastic materials are based on proteins, so they also require high melting temperatures and high pressures to be processed (thermoplastic extruders) or they are unable to adhere to hydrated surfaces (sometimes due to their high water content). In the case of using collagen or other proteins of plant origin (soybean, gluten, etc.) in compositions with other plasticizers instead of water (for example glycerol), although the result may have excellent mechanical properties, what is obtained is the thermosetting behavior of the composition (see US Pat. No. 8,153,176), which therefore cannot be used as a hot-melt plastic. 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 US Pat. No. 6,846,502-B1; and in JP-57,158,276, a hot melt adhesive composition made of edible ethylene vinyl acetate, a tackifying resin, and paraffin wax is also disclosed. All of these are ineffective at bonding to hydrated surfaces.

Other examples of useful resin compositions are those used to make capsules intended for encapsulating pharmaceutical agents. These capsules contain a dry or liquid pharmaceutical ingredient that, once swallowed, dissolves in the digestive tract and releases the active agent.

The protein composition of those capsules is mainly based on denatured collagen or its hydrolyzed derivatives such as gelatin.

Gelatin is a protein product obtained from the acidic or alkaline hydrolysis of collagen. It loses its original, natural triple helical structure, resulting in a random distribution of shorter segments of the polypeptide backbone—also known as α-chains of amino acids—and has an average molecular weight of less than 500 kilodaltons. Therefore, gelatin does not constitute a true solution; rather, it forms a colloidal solution or sol. Upon cooling, this sol transforms into a gel, and upon warming, it reverts to a sol. During the gelation process, gelatin molecules form a solid, three-dimensional structure. Water is retained between the molecules, and those below a certain temperature are interconnected by various physical bonds—primarily hydrogen bonds—that create a three-dimensional polymeric network. However, this water is able to flow and, for example, evaporate. The infinitely reversible gelation process is by far the most important technical property of gelatin. An analytical measure of gelling power is known as the bloom value. High-bloom gelatin is characterized by high melting and gelling points in the final product, as well as short gelling times. Commercial gelatin types have bloom values ranging from 50 to 300 blooms. The range of 50 to 100 grams is designated as low bloom, the range of 100 to 200 grams as medium bloom, and the range of 200 to 300 grams as high bloom.

The molecular weight distribution of gelatin is determined by the type and intensity of the hydrolysis process used. In the case of high-bloom gelatin (called type B) under alkaline conditions, the molecular weight fraction is mainly in the region of 100,000 g/mol, corresponding to the α chains, while gelatin under acidic conditions has a much broader distribution. The molecular fraction in the region of 100,000 g/mol has a greater influence on gel strength, while viscosity is mainly due to the molecular weight range of 200,000 g/mol to 400,000 g/mol and above.

By way of example, it is worth mentioning the compositions disclosed in patent documents No. US-4576284-A (-284A) and US-4591475-A (-475A), wherein the compositions are based on low-grade gelatin. In 284A, a gelatinous material based on 150 blooms of type B gelatin with a water content of 5% to 30% (which acts as a plasticizer) is disclosed. It should be mentioned that if a softer product is desired, some edible plasticizers such as glycerol, sorbitol, propylene glycol, etc. can be incorporated into the composition during the process, wherein the amount of the edible plasticizer incorporated is in the range of 0.5% to 40% by weight of the polymer.

In addition to plasticizers, the document (-475A) also discloses the addition of lubricants, colorants, and other polymeric substances for gelatin expansion (called extenders), such as other proteins or polysaccharide gums. Some crosslinking agents are also included. Document US-4655840 relates to a composition for injection molding, which is generally hydrophilic and, although preferably made from different grades of gelatin, can be modified by adding other natural hydrophilic polymers, mainly extracted from plants.

Unfortunately, resins based on, for example, gelatin in aqueous gel systems lack sufficient adhesion to hydrated surfaces such as collagen, and also lack sufficient cohesive strength in the molten state to function properly in a rapid and efficient operation such as that described in the present invention. No description is given of the mechanical properties of such resin materials, nor is their performance as adhesives in the solid or molten state.

Polysaccharide compositions also used for capsules are based on thermoplastic derivatives of cellulose and starch as primary sources, but can also be derived from other natural polysaccharides and their synthetic derivatives. Both polymers are generally hydrophilic. US Pat. No. 4,738,817 and MX-2010013731-A describe, for example, thermoplastic compositions based solely on polysaccharides such as HPMC or HPC, intended for injection molding of capsules.

On the other hand, the protein thermoplastics used in the manufacture of pet toys, due to their excessive rigidity, have an elastic modulus that deviates significantly from the requirements of the present invention. For example, in US Pat. No. 6,379,725, a mixture of plant and animal proteins, along with plasticizers and additives, is extruded to produce a colloid that, upon cooling, exhibits a modulus between 900 and 4000 MPa and a tensile strength between 20 and 40 MPa. It must also be emphasized that this composition is insoluble in water. Another protein thermoplastic composition based on collagen and water that can be used in the manufacture of animal products is described in International Application No. WO-2007104322-A1. In this case, however, the polymer is a partially denatured collagen with a solubility in water of at least 25% at 60°C, and the extruded product exhibits an elongation of 200% and a tensile strength of approximately 20 MPa.

The most serious drawback of all the described natural polymer compositions is the difficulty in finding a single resin that achieves the desired combination of physical properties, whether mechanical, thermal, adhesive, or even rheological, to perform correctly both during closure application and later as an effective tightening element for the closure, while also being edible and water-soluble. Resins based on natural polymers typically exhibit elevated melting temperatures, little or no adhesion to wet surfaces, such as collagen films with a moisture content of more than 15%, and (in the case of edible, shirred collagen casings) insufficient adhesion to achieve rapid welding on their own.

By reference to the viscosity properties, reference is made here to the international application number WO-2009045824-A2. Some mixtures mentioned in this document include gelatin and glycerol or fructose, which achieve a certain degree of viscosity when wetted in the solid state. This has been suggested for example for use in the production of surgical reinforcement materials to function in conjunction with surgical staplers, wherein the dry weight ratio of the polypeptide substance, e.g. gelatin, to the polyhydroxy material, e.g. glycerol, used is indicated to be in the range of 30:70 to 70:30. When the material is wetted in the solid state, it becomes an adhesive, e.g. on the ECM (extracollagenous matrix material). However, this property has no practical effect that can be applied in the closure of the present invention, because no matter what the water content of the collagen casing itself is

Neither (at least within the hydration range of interest to the present invention) has any wetting effect on the current closure elements, thereby rendering the present material non-tacky in the solid state.

Summary of the Invention

A first aspect of the invention relates to a closure that meets all the requirements presented above, as will become apparent from the following description of its main features and the examples presented below. Such a closure is achieved by using a non-invasive tightening element based on a thermoplastic and edible material, fastened and/or adhered to a short portion of the sausage casing that has been previously crimped by means of a shutter-like device and/or subsequently twisted, wherein said element preferably has the same properties as the sausage casing material itself and is even edible and capable of dissolving in warm water, so as to be considered safe when swallowed, even disappearing after handling or cooking the sausage.

As far as the shape and dimensions of this element are concerned, it should preferably be small so as to be contained once it forms part of the closure and to fit in a perfectly centered position inside the hole of the rod of the tucked casing, by applying a gentle force; it should also have a symmetrical plane of radial cross section so as to facilitate its degassing outside the hole when subjected to the impact of the meat, without risking rubbing against the internal folds of the rod, and also avoiding impacts on the brake ring of the filling machine.

Such an element also has certain characteristics which facilitate its application to a length of twisted casing in a sequence of steps which can be converted into the simplest possible steps by an automated system. Among these characteristics are suitable physical and mechanical properties, such as a low melting temperature, increased cohesive power 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 the already collapsed casing section, which requires special physical properties (high modulus) with regard to flexibility and toughness, wherein the system is based on the tightening force exerted by closed and welded annular elements to clamp, thereby strongly tightening a section of the casing and thus preventing the ring from slipping due to pressure.

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

The ability of this type of fastening element to adhere to the casing surface in the molten state is therefore another important advantage for the correct functioning of some embodiments of the closure, since accidental slippage of the fastening element on the surface it surrounds would result in the closure being opened when the casing is pushed by the meat emulsion during filling. However, it must be emphasized that the adhesive and fastening abilities play complementary roles in the closure of the present invention, although the importance of each varies depending on the type of casing and its caliber. It may be the case that a small caliber can be kept securely closed by tightening the annular element of the present invention, which has a weaker level of adhesion on the hydrated surface but a sufficiently high modulus to apply a strong tightening pressure to the surrounded strand of the twisted casing in order to prevent further slippage.

We have surprisingly found that a closure element that meets all of the aforementioned requirements can be an annular constricting element made of a thermoplastic material and essentially consisting of dry gelatin and anhydrous glycerol, provided that the water content of the total weight of the composition does not exceed 15%. This thermoplastic material can be welded at low temperatures and has mechanical properties between viscoelastic and plastic behavior, which allow it to exert a sufficient constriction to withstand the sausage filling process while being edible and water-soluble.

Yannas and Tobolsky studied the viscoelastic behavior 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 anhydrous gelatin rubbers. J Appl Polymer Sci 1968; 12(1): 1-8), however, no data on a systematic study of the adhesive properties of such compositions in the molten state have been reported.

Surprisingly, the mixture of dry gelatin and anhydrous glycerol yields a thermoplastic solid that acts as a hot melt material characterized by a very low Tg (glass transition temperature) and a relatively low Tm (melting temperature), characteristics that are highly desirable for the working conditions required for the closure of the present invention, wherein the transition from the solid phase to the liquid phase demarcates the transition between the adhesive and non-adhesive states, wherein the liquid phase has high cohesive power and viscosity, and wherein its transition to the solid phase is rapid due to the low Tm, which allows the welding of the material to occur sufficiently quickly. However, solid resins have no cohesive power at ambient temperature.

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

The required and desired mechanical properties summarized in terms of Young's modulus can be adjusted via the ratio of gelatin to glycerol in the composition; in this way, a wide range of plastic behavior from less flexible or less rigid to more flexible or more rigid can be obtained within a very narrow range of melting temperature (Tm) and cohesive force, which is very advantageous from the point of view of the efficiency of the sealing process.

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

The mechanical properties of this ring-shaped element are extremely important, as it must not only be sufficiently flexible to allow for a non-destructive closure during the closing operation, but also possess an appropriate elasticity (Young's modulus) to withstand the expansion caused by the pressure of the air or meat from inside the casing during the filling process, and to securely maintain the contraction of the enclosed casing segment. If the ring yields to this expansion stress, like an elastic rubber, the meat will be able to find its way through the closure and escape. The higher the modulus, the less elastic the material, while, conversely, the lower the modulus, the more elastic it is.

Solid resins behave like plastics, and their properties vary under the influence of the molecular weight, bloom value and the proportion of the polymer in the resin composition. The higher the molecular weight and bloom value (>150 bloom), the greater the viscosity and therefore the adhesion.

We have found that in order to have the correct properties and avoid all the disadvantages mentioned, the loop material must conveniently have a modulus of at least 0.5 MPa and preferably not more than 50 MPa. In this sense, the best results are achieved in combination with gelatin having a high bloom, conveniently greater than 150 bloom, preferably greater than 200 bloom, since this grade of polymer gives the thermoplastic composition the best adhesion at room temperature.

Melting point:

Once the heat seal closure is transferred to the machine, the melting point of the ring's material and the speed at which it can fuse to itself are crucial for the closure to be effective. 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 the process, the safer and easier it is to use the system.

Yannas and Tobolsky set the melting temperature of slightly hydrated gelatin at 175° C. ± 10° C. It is well known that in a binary composition such as gelatin and glycerol, where the solid components dissolve in the other components, the solidification point of the composition can be lowered by increasing the concentration of the component with the lower solidification temperature, which will lower the solidification temperature of the mixture.

The melting temperature of this resin combination changes with the ratio (gelatin/glycerol ratio) of polymer, and this polymer ratio increases and makes this melting temperature higher.But, should reach compromise between plastic properties, the adhesiveness of melting temperature, resin in this molten state and the cohesive force that improves are correspondingly associated with the rapid setting time of the welding of this material.Along with the increase of this ratio, the viscosity of material in the molten state also increases, but the total water content of composition is lower, and this material adheres to the ability of the moistening surface of collagen film and increases significantly.

We have found that the optimal temperature range for implementing the loop closure process is between 40°C and 90°C, as such temperatures do not affect the integrity of the collagen casing. We have found that a polymer/polyol ratio of approximately 1:1, and closer to 1:2 or even higher, allows for rapid weld formation. Within this ratio range, a large variation in mechanical properties is achieved without a significant increase in melting temperature, while the cohesive force of the melt is high, allowing for rapid weld formation at the moment of contact between the two surfaces, with only a slight drop in temperature required. In this regard, we have also found that the gelatin must preferably have an elevated degree of polymerization, meaning an elevated bloom, particularly above 150 bloom, and more preferably from approximately 200 bloom to approximately 300 bloom.

Adhesion:

The faster the weld sets, the faster the closing step is and the more effective the closing system is.

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

Water solubility of locking ring:

Another important factor in the base resin of the locking ring of the closure of the present invention is its water solubility, as sausage products in edible collagen casings with the closure of the present invention undergo a cooking process before packaging. During normal processing, temperatures rise above 70°C, and it may be appropriate for the ring to disappear or remain during this cycle—for example, if the ring is used as a marker. Therefore, the solubility of the resin material of each composition under normal processing conditions is also reflected in Table 1:

The pressed ring is soluble in hot water and can be completely dissolved in water at 81.5°C in 35 minutes. If the ring needs to remain stable for longer periods of time, the gelatin can be replaced by partially denatured collagen, such as that used in International Application No. WO-207104322-A1, or a cross-linking agent that can insolubilize the polymer by creating covalent bonds, as is known in the art, can be used. Such cross-linking agents are preferably food-grade cross-linking agents, such as aldehydes, in very precise amounts.

Parameter measurement:

Tensile properties of plastics:

Tensile tests were performed according to ISO 527-2:2012/5A/50 using a ZWICK universal tensile tester (code MO 0217-2, at least type 1 according to ISO 9513) and self-clamping pliers (code MO02/17) at a testing speed of 50 mm/min. A grip distance of 50 mm was used. Type 5A specimens were obtained by punching. Prior to testing, the specimens were conditioned for 16 hours at 23 ± 2°C and 50 ± 10% RH. Laboratory conditions were 23 ± 2°C and 50 ± 10% RH.

Melt index:

This test measures the viscosity of molten thermoplastics; this parameter is selected to evaluate the change in the adhesive strength of thermoplastic compositions as a function of temperature. This test is performed using a flow meter coded MO 02/16, as specified in UNE EN ISO 1133-1:2012. The nozzle used has a length of 0.025 ± 8.000 mm and a diameter of 2.095 ± 0.005 mm. The piston travel distance is 30 mm. The pre-melting time is 5 minutes. The test conditions are: a) temperatures of 120°C, 100°C, and 80°C; b) sample loadings of 1.2, 5.0, and 21.6 for a 1:2 ratio. No cutting time is used.

Determination of thermal transitions by differential scanning calorimetry (DSC):

This measurement was performed in accordance with ISO 11357:1997 on a Perkin-Elmer Pyris Diamond MO 01/21 calorimeter using a representative sample of 5 to 10 mg in an aluminum crucible under a nitrogen flow. Indium and zinc were used for the standard mode. The results were averaged from two measurements. The determined value was used for the second scan. The test parameters were: a) initial temperature = -60°C; b) final temperature = 150°C; c) heating rate = 20/min; d) cooling rate = 20/min.

Adhesion:

Adhesion was tested on flattened sausage casings equilibrated in a climate chamber at 85% RH until the casings reached moisture contents of 12%, 21%, and 35%. Each resin was melted on a steel plate and cast onto a stretched sausage casing sheet, which had been stretched to approximately 3 cm wide and 10 cm long by a pre-molded film. The resins were allowed to cool for 5 minutes, and then the peel strength was measured using a dynamometer at 90°C.

Tack at room temperature is judged by the adhesive's adherence to a person's finger.

Residual moisture:

The apparent water content in the preparation of this composition was determined by drying the gelatin powder in an oven at atmospheric pressure and 105°C for 24 hours. The data obtained provided the basis for calculating the residual water content in the binary composition formed from commercial gelatin and glycerin. However, when it comes to the change (reduction) in the residual water content in the composition, the drying process was carried out in an oven at a vacuum pressure of ^10-3 mm Hg and a temperature between 25 and 105°C. This calculation was performed by taking the weight of the test sample.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of supplementing the description made and for the purpose of facilitating a better understanding of the characteristics of the invention according to a preferred practical example embodiment thereof, a set of drawings is attached as an integral part of said description, the following being shown with an illustrative and non-limiting character:

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

FIG2 shows how a worm with longitudinal grooves of V-shaped cross-section reaching the axial hole can be molded so that any section cut transversely from the worm has an annular opening in the form of a "c". FIG2 shows a tightening element that is a solid annular element made of an edible and water-soluble thermoplastic composition, having a smoothly curved V-shaped inlet gap that opens into a central hollow, while FIG2b shows another embodiment in which the annular element is made of a gelatin/glycerin ratio that allows the ring to exert a strong tightening effect on the twisted portion of the casing, while the same composition material has sufficient elastic behavior to allow the ring to be opened without breaking during the short period of time required to maintain the fit of the twisted string of casings.

FIG3 shows three diagrams, in which FIG3a shows the end of a shirred casing strand captured by a forceps located at the end of a rod, the axis of which coincides with the axis of the strand. The rod retracts and pulls the strand until the unshirred section of casing does not exceed 5 cm. At a point between the connection of the shutter member to the shirred section (approximately 10 mm into the casing) and the point where the forceps are gripped, the shutter member (motorized iris diaphragm) rapidly closes its blades and collapses the unshirred casing, as shown in FIG3b. Furthermore, while the shutter member is closing, the forceps rod rotates on its axis and twists the remaining casing section, thereby creating a string (string) approximately 3 cm long along the axis of the shirred casing strand, as shown in FIG3c.

FIG. 4 shows an open ring of thermoplastic material being closed by a movable jaw to produce an annular form.

FIG. 5 shows a detailed view of FIG. 3 a .

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

FIG10 shows the rod of casing finally obtained.

DETAILED DESCRIPTION

A preferred embodiment of the closure portion.

In the preferred and simplest embodiment, the closure of the invention consists of a short section of twisted casing, which is clamped by a tightening element. The tightening element is a solid annular element made of an edible and water-soluble thermoplastic composition, which has a smoothly curved V-shaped entry gap that opens into a central hollow part (see Figure 2a), where the previously tightened and/or twisted section of the casing is positioned by pushing it with a wedge.

The ring can be manufactured by any method known in the art of plastic molding and it can be welded with multiple repeating elements (rings) connected to each other by weak seams in the strands or rods (as shown in Figure 1) - like staples in a stapler - to facilitate the machinability of the feeding process of the ring unit, and in this way, all the rings are opened before individual use.

Thermoplastic composition

The current thermoplastic composition comprises dried gelatin, anhydrous glycerin, and water. The water content does not correspond to the residual water remaining after drying commercial gelatin (whose initial water content typically varies between 10% and 13%) and is not practically usable except to prevent crosslinking of the gelatin. The water content of the composition should be less than 15%, preferably between 1% and 10%, and most preferably between 2% and 3%.

In view of all that has been revealed above, the most suitable gelatin is one of the food grade gelatins with a density greater than 150 bloom, preferably between 200 and 300 bloom; since the molecular weight distribution of this grade of gelatin corresponds to larger molecules, it provides a higher binding force for the resulting resin. An example of a commercial gelatin with relevant characteristics is one of the types A or B from Gelita AG (f.e. Gelita Hardgel, G.RXL, G.Advanced, G.PA, etc.) of Germany, wherein the characteristics of this commercial gelatin include: 8-30 mesh, 200-300 bloom, viscosity 25-55, and water content 8.5-12.0%; another is Juncá Gelatine (Mikel Juncá Gelatines, Banyoles, Girona) within the same range of characteristics 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 the rods with connected rings

The composition can be homogenized by well-known methods in a single-screw extruder such as a Rheomex 302 or a co-rotating twin-screw extruder such as a Krupp Werner & Pfleiderer ZSK25. The pressure inside the co-rotating twin-screw extruder increases, and the shear forces acting on the mixture as it passes through the extruder increase, while the temperature is raised significantly 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°C. During the plasticizing process, the pressure inside the extruder is generally low relative to the pressure during the subsequent injection molding process. The pressure during mass plasticizing is typically between 20 and 75 bar, depending on the polymer/polyol ratio in the composition. The plasticized resin can be directly or, preferably, in the next step, injected into one or more mold cavities for injection molding using conventional methods. Once the plasticizing step is complete, the material is extruded through a die with regular circular holes into endless strands, each with a diameter of 2 to 4 mm. The strands are then cooled and pelletized in a conventional pelletizer. The pellets are then passed on to the next injection molding operation, where the pressure inside the extruder is increased to 70 to 120 bar. Finally, a solid body with connected rings in the shape of a rod or worm is obtained, which, after cooling, can be ejected from the mold when the mold is opened.

It goes without saying that this injection molding operation can be used not only to manufacture continuous rings in the form of a worm, but also to manufacture individual rings, however, the choice should depend on how the closed machine is designed in order to achieve its optimal performance.

In order to modify (reduce) the residual moisture content of the molded solid bodies, the process takes place in an oven at a vacuum pressure of 10 ^-3 mm Hg and a temperature between 25 and 105° C. The calculation of the hydration level is performed by taking the weight of the sample before and after the drying process, assuming an initial moisture content derived from the official specifications for the raw materials.

The worm-like piece can have a length of several centimeters and an external diameter of 6 to 8 millimeters, depending on the diameter of the hole of the strand of pleated casing. The diameter of the longitudinal hole (axial hole) of the worm-like piece ranges from 1 to 4 mm, depending also on the thickness of the rope of twisted casing to be surrounded. The worm-like piece is molded with a longitudinal groove of V-shaped cross section, which reaches the axial hole so that any section cut transversely from the worm-like piece has an annular opening in the form of a "c", as shown in Figure 2. The opening (1) (gap) is the path through which the crimped section of the twisted rope is fitted into the hollow part of the ring of the fastener.

ring

A tightening element or ring according to the present invention can be cut from a molded worm-shaped preform ( FIG. 1 ), rather than being manufactured individually, by cross-cutting the worm-shaped preform to obtain a plurality of rings. The worm-shaped preform is given a segmented appearance by uniformly arranged constrictions, thereby imparting a ring-like shape.

A ring composed of a gelatin-based edible resin thermoplastic composition can exhibit the following essential characteristics once placed around a collapsed casing segment:

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

b) have sufficient modulus of elasticity (even if not too much toughness) to apply sufficient radial tension to the twisted/tightened portion of the casing to which it is fastened, and

c) It is safe, edible and water-soluble.

In a preferred embodiment, the annular element is composed of a gelatin/glycerol ratio that gives the composition a modulus higher than 10 MPa and more preferably higher than 20 MPa, this modulus being sufficiently increased to allow the ring to exert a strong tightening action on the twisted portion of the casing, while the same composition material has sufficient elastic behavior to allow the ring to be opened without breaking during the brief period of time required to maintain the fit of a string of casings (see Figure 2b).

In another preferred embodiment, the constricting element is a solid annular element similar to the constricting element described above, which is open before being placed around the pre-tightened portion of the casing (see Figure 2a), and then closed and heat-sealed to maintain a secure constriction on the casing material. This is all possible because the thermoplastic composition from which the ring is made can be welded to itself by low temperature heating and by having the property of rapid weld solidification.

The opening (1) of the C-shaped ring is the path through which the ring fits over the shrunken and/or twisted section of the casing, in other words, the position through which the casing section enters the ring towards the center of the ring. Once the section of casing is fitted over the central hollow of the ring, the opening (1) is mechanically closed. The closing operation itself consists of heat-sealing the now connected ends of the C-shape and welding the ring on the enclosed section of the casing.

Since the split ring made of thermoplastic material is closed by the mobile clamp (Figure 4) to create the annular form, the two opposite parts of the split are previously melted by contact with metal wedge elements heated at a suitable temperature so as to fuse at least one contact surface; the two surfaces are then brought closer until they are in contact. At this time, it is important that, in addition to the pressure exerted by the clamps forcing the closure, the slight decrease in the initial contact temperature also promotes a rapid increase in the bonding force of this weld of the materials to be solidified. Before complete solidification, this bonding force is already large enough to prevent the ring from opening (weld setting) and avoid premature loosening of the clamping of the newly formed ring once the clamps are released.

Closed operation procedures

The enclosing operation is a loop that proceeds as follows:

a) One end of the shirred casing strand is captured by a pair of pliers (Figure 3a, not shown) located at the end of a rod whose axis coincides with the strand's axis. The rod retracts and pulls the strand until the unshirred portion of the casing is no more than 5 cm. At a point between the shutter's connection to the shirred portion (approximately 10 mm into the casing) and the point where the pliers are gripped, the shutter (motorized iris diaphragm) rapidly closes its blades and collapses the unshirred casing (Figure 3b).

b) While closing the shutter, the forceps rod is rotated on its axis and twists the remaining casing section, creating a string (string) approximately 3 cm long in the direction of the axis of the strand of shirred casing ( FIG. 3 c ).

c) The open C-shaped locking ring is moved upward beneath the newly formed string of casings. The ring is clamped inside the open jaws of the clamp-type device by an open, tightening clamp, which simultaneously closes the ring and cuts the string. The ring moves upward to fit the string of casings within its axial hollow portion, with the ring's opening forming an upward-facing "V." The clamp stops raising when the ring's axis coincides with the string's axis.

d) As the locking ring is raised, a push rod is lowered to push a string of casings into the hollow portion of the ring (Figure 7). The ends of the rod are made of steel with flat wedges and straight edges and are kept preheated to a temperature sufficient to melt the resin ring. The axis of the rod coincides with both the direction of the ring's rise and the axis of the ring. As the rope fits into the axial hole of the ring, the push rod contacts and melts a layer of the opposing surfaces to be joined, at least on one side, but preferably on both sides, thereby sealing the ring.

e) As the push rod moves away again, the clamps carrying the ring (Figure 8) close, causing the contact surfaces on the twisted casing rope to fuse together while, on the other hand, cutting off the excess end of the casing. The clamps exert a moderate, continuous force on the ring for a predetermined time, which can vary from 2 to 5 seconds. After this welding time, the clamps open and descend to their rest position, where they are loaded with the next clamping ring.

f) The shutter piece snaps open. The ring is closed and the weld is also effected on the body section embedded therein and in a further optional step.

g) The closure is pushed inside the shirred rods of the casing (holes).

Other variations of the present invention

It is also envisaged in the present invention that after the closing operation, the casing can be turned inside out, or the closing portion can be introduced into the inner cavity of the rod so that the annular closing portion is located in the inner hole of the rod (as shown in FIG. 13 of EP-2266410, where the ring should surround the point marked 14). After filling, the closing portion of the present invention can remain on the outer surface of the sausage or on the surface that contacts the sausage. In this case, some of the closing portion can still be present after cooking, which should not cause problems as the closing portion is edible.

The ring of the present invention may have other shapes such as hexagonal, etc., and is not necessarily circular. Moreover, the ring is not necessarily edible (can be applied to other casings) nor water-soluble.

Example:

Example I: Preparation of different composition samples.

For this embodiment of the composition, a food-grade gelatin powder of 240 to 260 blooms, with an average particle size (0.3 to 0.8 mm, corresponding to 20-50 mesh, in this case specifically 35 mesh), with an apparent water content of 13% was used from Juncá M. (Girona, Spain). To obtain compositions with increasing gelatin/glycine ratios 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, resulting in compositions with different apparent water contents, as shown in the following table:

To obtain compositions with an increasing gelatin / glycerol ratio between 2: 1 and 1: 2.5, in each case 100 parts of commercial gelatin with a residual water content of 13% are taken, combined with the appropriate part of anhydrous glycerol, to obtain compositions with various contents in apparent moisture as shown in the following table:

The polyol was food grade anhydrous glycerol from Sigma-Aldrich. The composition was prepared by dissolving gelatin directly in commercial glycerol with vigorous stirring at temperatures varying between 80 and 120° C. The resulting ratios expressed in Table X refer to the weight ratios of the pure products without water.

Table 1:

Example II: Determination of melting temperature:

The thermal transitions were determined by differential scanning calorimetry (DSC) from the samples prepared at different composition ratios in Example 1. The average results are listed in the following table:

Table II:

Tg = glass transition temperature; Tm = melting temperature.

Example III: Determination of rheological coefficient.

Table III:

MVR means melt volume ratio.

It is clear that the change in the ratio of gelatin to glycerin leads to a sharp drop in fluidity (and thus an increase in viscosity and, therefore, bonding strength), thereby reducing the applicable temperature. This provides an idea of what is the most appropriate combination for the annular closure of the fastener of the present invention, namely, for optimal welding performance and rapid fixation of the weld when executed at relatively low ambient temperatures.

Example IV: Determination of the elastic modulus

The tensile properties of the various samples from Example 1 were calculated using ASTM method D638-10 (equivalent to ISO 527-2), which specifies test conditions for determining the tensile properties of molded and extruded plastics, based on the general principles of ISO 527-1 for dogbone-shaped samples. The tests were performed using dogbone-shaped samples. The results are listed in Table IV.

Table IV:

It can be observed in the table that the elastic modulus increases sharply between the transition from a ratio of 1 to 2. Example V: Determination of Adhesion

Adhesion was tested for various samples prepared according to all samples of Example I. In addition, the composition contents of polymer/diluent (gelatin/glycerol) corresponded to a ratio of 2:1, and the composition with a residual moisture content of 9% was dried in an oven at 60°C and a vacuum pressure of ^Hg10-3 mm Hg until reaching different moisture contents of 6%, 3%, 1.5% and 0.5% (corresponding to samples A7 to A10, respectively).

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

It is also noted that compositions having very low water contents have inherently increased adhesion once melted, particularly the higher the amount of polymer in the resin.

Unpeelable means that when an attempt is made to peel a piece of resin film from a surface of a body to which the resin film is cast by melting, the resin film, once cooled and solidified, is able to pull and drag material from the body without separating therefrom.

Example VI: Preparation of a rod of a sealing/fastening ring made of gelatin and glycerol by injection molding.

As depicted in FIG1 of the accompanying drawings, a plurality of hollow worm-shaped rods with longitudinal V-shaped openings were molded by injection molding. The starting composition of the extruded resin material consisted of 200 blooms of gelatin (Juncá), glycerol (food-grade glycerol purchased from Sigma-Aldrich), and a residual amount of water, with the final proportions of the components in the mixture corresponding to samples A4 and A8, respectively. The dimensions of these elements for each composition were, on the one hand, 20 cm in length and 8 mm in diameter, with a central hollow portion having a diameter of 2 mm; on the other hand, 12 mm in diameter, with a central hollow portion having a diameter of 4 mm.

The material is plasticized and extruded using a single-screw extruder widely used in the plastics processing industry, operating at temperatures between 87°C and 104°C and pressures of approximately 50-100 bar. The plasticized material is extruded through a circular die with six holes, each 2 mm in diameter. The cooled, endless strands are then pelletized in a conventional pelletizer. The pellets are used to produce worm-shaped rods on a conventional injection molding machine. The material is then injected into a stainless steel mold at a pressure between 1000 and 1200 bar, from which the molded part is removed. The rods are placed on a rack and allowed to dry until their moisture content reaches 2% to 3%. The resulting rods are flexible and strong.

By cutting the rod in a transverse manner with a cutting tool, a number of 8 mm short segments are obtained. The cross section of each segment has the shape of an open ring or C-ring. The opening of this C-ring is the path through which the collapsed and/or twisted casing segment is inserted into the ring.

Example VII: Embodiment of the closure; 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; namely, caliber 21, where small rings (8 mm diameter) made from the compositions designated A2, A4 and A8 were applied; and caliber 28, where 12 mm diameter rings made from the same compositions were applied.

In each case where the pleated rods were manually sealed, one rod was advanced to deflate approximately two inches of casing, and then the manual shutter member was used to collapse the extended casing within one inch relative to the beginning of the pleating rod. The remaining portion of the casing, once gripped by the shutter blades, was twisted to form a string approximately two millimeters in diameter for a 21-caliber casing and approximately four millimeters in diameter for a 28-caliber casing.

Table VI: Results of the resistance of the closure to the filling process

The annular closures made from each composition are applied directly, by selecting the dimensions as indicated. Half of the ring of each composition and diameter is sealed as described in the memory, using a heater with a trapezoidal head for tinning, heated to 85°C. The heater is initially used to push the string of casings into the central hole of the ring; once fitted, the sides of the heater come into contact with the contact surface of the ring, causing rapid melting of the surface layer; the heater is then removed, and this process occurs simultaneously with the closing of the ring. Once the melted surfaces of the ring are in contact, removing the closing pressure within 2 seconds allows a weld with sufficient adhesion to be formed. After the pressure on the ring is removed, the ring remains closed, forming a tightened ring. The other half of the ring is not welded but is simply pressed after the casing has been fitted into its central hole.

The shirred and sealed casing rods were filled with sausage meat on a Robby Vemag 2 machine at a rate of 80 portions/minute using the brake control of the filling machine.

The results of the filling process are listed in Table VI. As reflected in these results, the rings made from composition A2 that were not sealed were relatively able to withstand the filling process, with larger rings, based on their diameter, having a greater resistance to opening, depending on the corresponding pipe diameters to which they were applied. In the case of the smaller rings made from composition A2, their smaller wall thickness, coupled with a lower elastic modulus, also facilitated some of them opening during the filling process, thus recommending their use in these cases.

The sausages were then hung on hooks and baked at 90°C for four hours in a simple cycle. In all cases, the first sausage—the carrier of the ring—remained intact until the start of the cooking cycle. During this cycle, the meat filling solidified, and the sausages maintained their shape until the end of the cycle. During this time, the sealing ring of each first sausage gradually dissolved, disappearing before the end of the cycle. The end result was satisfactory, not only due to the excellent sealing performance, but also because using the sausage to carry the closure offered a more realistic possibility than using other parts in the same manner.

Claims (20)

1. A tubular casing for food made of an edible collagen membrane, the tubular casing having an end closure; the end closure being located at a section of the casing, wherein the section of the casing is radially compressed and/or twisted toward its axis such that the section of the casing acts to block internal pathways located therein; and wherein the compressed/twisted section of the casing is continuously surrounded, secured, and tightened by a solid annular element, the solid annular element being wholly or partially fused to the surrounded portion of the collagen casing, and wherein the solid annular element is made of a thermoplastic and edible material. 2. The tubular casing according to claim 1, wherein the tubular casing is pleated. 3. The tubular casing according to claim 1, wherein the thermoplastic material of the solid annular element is an edible thermoplastic composition based on proteins, polysaccharides, or mixtures thereof. 4. The tubular casing according to any one of claims 1 to 3, wherein the Young's modulus of the thermoplastic composition of the solid annular element, measured under environmental conditions of 23°C and 50% RH, is in the range of 0.5 MPa to 50 MPa in the solid state. 5. The tubular casing according to claim 4, wherein the thermoplastic composition of the solid annular element has a melting temperature (Tm) between 40°C and 98°C. 6. The tubular casing according to claim 1, wherein the thermoplastic and edible material of the solid ring element is a non-crosslinked and water-soluble protein thermoplastic composition comprising a mixture of dry gelatin and polyols, and wherein the water content by weight is in the range of 0.5% to 15%. 7. The tubular casing according to claim 6, wherein the water content in the thermoplastic and edible material of the solid annular element is between 1% and 5% by weight. 8. The tubular casing according to claim 7, wherein the water content in the thermoplastic and edible material of the solid annular element is between 2% and 3% by weight. 9. The tubular casing according to claim 6, wherein the thermoplastic and edible material of the solid annular element is a cross-linked and water-insoluble composition. 10. The tubular casing according to any one of claims 6 to 9, wherein the gelatin has a Bloom value higher than 150. 11. The tubular casing according to any one of claims 6 to 9, wherein the polyol is glycerol. 12. The tubular casing according to any one of claims 6 to 9, wherein the Young's modulus of the protein thermoplastic composition of the solid ring element, measured at 23°C and 50% RH, is in the range of 0.5 MPa to 50 MPa in the solid state. 13. The tubular casing according to any one of claims 6 to 9, wherein the protein thermoplastic composition of the solid ring element has a melting temperature (Tm) between 40°C and 98°C. 14. The tubular casing according to claim 1, wherein the thermoplastic and edible material of the solid annular element is a polysaccharide-based thermoplastic composition comprising cellulose fibers, the cellulose fibers comprising microfibers and nanofibers mixed with other components selected from the group consisting of starch, methylcellulose, hydroxymethylcellulose, hydroxypropyl methylcellulose and mixtures thereof. 15. The tubular casing according to claim 14, wherein the Young's modulus of the polysaccharide thermoplastic composition of the solid ring element, measured at 23°C and 50% RH, is in the range of 10 MPa to 50 MPa in the solid state. 16. The tubular casing according to claim 15, wherein the polysaccharide thermoplastic composition of the solid ring element has a melting temperature (Tm) between 40°C and 98°C. 17. A stick of a pleated tubular casing made of an edible collagen membrane, having an end closure of the tubular casing according to any one of claims 1 to 16. 18. A method for obtaining an end closure portion of a tubular casing according to any one of claims 1 to 16, characterized by the following steps: a) Provide a section of smooth or unpleated tubular casing; (b) Provide a batch of molded open C-shaped rings according to the specification and drawings, said C-shaped rings being made of the thermoplastic and edible composition according to claims 1 to 12. c) Clamp and twist a very short, very short section of the casing from step a) to form a very short section; d) The twisted strand obtained in step c) is pushed through the inlet gap of the C-ring and inserted into the interior of the C-ring until the longitudinal axis of the strand coincides with the axis of the hollow portion of the C-ring; or alternatively e) According to step d), the twisted strand portion is pushed by a thrust element located on at least one side and inserted into the hollow portion of the C-ring, and a heat source is applied until the twisted strand portion fits into the hollow portion of the C-ring; then the thrust element is retracted and the C-ring is securely closed until the opposing sides of the two top ends contact each other to weld the contact portion between the two top ends and the contact portion between the C-ring and the twisted casing strand portion currently wrapped in the C-ring; f) Maintain the closing pressure on the C-ring for 0.5 to 5 seconds, and then release the closing pressure to release the resulting closure. g) Cut off the remaining end of the strand portion, and h) Insert the annular end closure into the hole of the gathered leg portion. 19. The method for obtaining an end closure of a tubular casing according to any one of claims 1 to 16, as described in claim 18, wherein step g) and step e) are performed simultaneously. 20. A food product having a tubular casing made of an edible collagen membrane and having an end closure portion of the tubular casing according to any one of claims 1 to 16.