RU2335907C2 - Method of manufacturing food products polymer casing with pseudofibrous appearance and polymer casing manufactured by method - Google Patents

Abstract

FIELD: food products, manufacturing techniques.

SUBSTANCE: polymer hose casing for sausages, hot dog sausages, small sausages, processed cheeses and so on is produced. It comprises close lenticular cavities looking like fibers and in appearance it is similar to fibrous protein and cellulose sausage casings. The method implies extrusion of the hose with outer layer of polymer composition based on aliphatic polyamide which contains coarse phase of hydrophilic polymer plasticised by liquid plasticiser and following biaxial orientation and thermofixation. The boiling temperature of the plasticiser is lower than the temperature of the melt at the extruder delivery end. Outer layer can be the only one. The one-layer casing can be used for packing products subject to smoking.

EFFECT: invention allows minimising tearings of casing during orientation stretching, increasing productivity of extruding line and reducing casing cost.

20 cl, 13 ex, 3 tbl

Description

The present invention relates to a method for producing polymer shells for food products, as well as to polymer shells for food products obtained by this method, in particular to shells for sausages, sausages, sausages, processed cheeses, etc. In one embodiment, the shell has a high permeability in relation to smoke and water vapor and is intended for cooked smoked and raw smoked sausages.

In the production of sausages, traditional intestinal and artificial protein casings have traditionally been used. Such shells are distinguished by a dull appearance and roughness (natural) or fibrous structure (protein). Both the one and the other type of shells have insufficiently high barrier properties with respect to oxygen and water vapor and are not mechanically strong enough.

Artificial shells made of thermoplastic polymers, mainly polyamide, are devoid of these disadvantages. However, such casings, for the most part, are too “unnatural” in appearance, characterized by luster and tactile smoothness, which are not typical for protein casings that are usual for sausage consumers. Repeated attempts have been made to create plastic shells with an appearance and tactile characteristics that mimic the surface of protein shells.

In the application DE 10337010 A1, publ. 03/17/2005, a sleeve film of at least one layer, permeable to smoke, was disclosed, which includes a mixture of polyamide and natural fibers, mainly cellulose, as well as its manufacturing technology. The production of tubular film is carried out by (co) extrusion. The raw materials in the extruder are melted, homogenized and forced through a die, forming a seamless sleeve. The primary sleeve emerging from the extruder is cooled by air or water, then is simultaneously stretched in two directions, preferably by the double bubble method, and can then be thermofixed. This shell in appearance resembles fibrous collagen shells and is proposed as a substitute for them. Although the shell is claimed to be single- or biaxially oriented in the main embodiments, it is well known that polymeric materials containing fiber fillers are difficult to orientational drawing and often break during this operation. In addition, fibers from 5 μm to 10,000 μm (1 cm) in length can clog the filter mesh in the extruder adapter or, if there is none, an extrusion nozzle. Thus, the manufacture of a sleeve film according to this invention is associated with frequent shutdowns of the production line and unproductive losses of working time and raw materials.

In the application DE 10208858, publ. September 11, 2003, single-layer artificial shells made on the basis of block copolymers containing blocks of aliphatic and / or partially aromatic copolyamides and blocks of polyglycols containing monoglycol residues, as well as plasticized starch and / or products of its modification, are disclosed. Aliphatic polyamides, for example PA-6.66, may be included in their composition. The appearance of such membranes resembles natural intestinal membranes. Thus, these shells can be characterized as optically matte, with a rough surface. However, they also do not possess a pronounced fibrous appearance. The production of shells according to this invention is carried out by the method of (co) extrusion, followed by orientation and heat setting. However, the production process of these films requires a preliminary stage of plasticization of starch or carbohydrate, which is carried out in a twin-screw extruder, followed by processing of the thermoplastic mixture after extrusion into granules, which increases the cost of the shell made according to the invention. In addition, such shells have too strong adhesion to the sausage meat, which leads to a violation of the integrity of its surface when removing the shell. This application is a priority for the following two applications: WO 03/073861 and WO 03/073862.

In the application WO 03/073861 A1, publ. 09/12/2003, a food and water vapor permeable shell made of a thermoplastic mixture is declared which contains at least one aliphatic polyamide and / or copolyamide, one inorganic and / or organic filler and one aliphatic and / or an aromatic copolyamide having glycol and / or polyglycol units. As a filler, carbohydrates selected from a natural polysaccharide and / or its derivative are used; branched and cross-linked polysaccharides and their derivatives, as well as synthetic thermostable fibers or powders based on polymers. Inorganic fillers or reinforcing materials are also used, such as fiberglass, glass fibers, mineral wool fibers, talc, clay, etc. By varying the grain size of the filler, its type and mass fraction, it is possible to control the surface roughness of the shell, while the shell externally becomes similar to the natural intestinal membrane.

Single and multilayer shells with a matte rough surface that gives the impression of natural, are disclosed in the application for invention WO 03/073862 A1, publ. September 12, 2003. For their manufacture, the composition of the thermoplastic mixture is the same as in the application WO 03/073861. In a preferred embodiment, the thermoplastic mixture consists of at least one (co) polyamide and at least one organic and / or inorganic filler. The proportion of (co) polyamide in this case is 50-99 wt.%, Preferably 65-98 wt.%, And the total proportion of organic and / or inorganic filler is 1-50 wt.%, Particularly preferably 2-35 wt.% From total weight of thermoplastic mixture. As an organic filler, vegetable as well as synthetic thermostable fibers or powders are claimed. Introduced fillers create only a rough microrelief of the shell surface, but not the external fibrous effect.

The prior art methods for producing foamed plastic products, including films containing cavities in a matrix of a polymer material, which consist in introducing substances into the extrudable polymer material that decompose during extrusion to form gases, are known.

In the closest patent application DE 10125207 A1, publ. November 21, 2002, a smoke-permeable seamless biaxially oriented and thermofixed sleeve casing for food products based on polyamide and a method for its production are disclosed. It is especially suitable for use as an artificial sausage shell for smoked sausages. The shell contains bubbles or vacuoles in the form of a ball, lens and oval, which significantly improve smoke permeability. In addition to polyamides, the composition of the film includes highly elastic copolymers (elastomers) containing blocks of polyamide and simple or complex aliphatic ether, and substances that form bubbles. The substances that form the bubbles are divided into 2 groups. Some of them are practically inert substances, which, when the shell is oriented, cause the formation of vacuoles in it, others - reactive substances, which, under the influence of heat and radiation, emit gas that forms bubbles in the film. The first group includes fine-grained inorganic particles having a relatively low adhesion to polymers, for example calcium carbonate, barium sulfate, or iron oxide (III). The second group includes fine-grained inorganic and organic blowing agents that thermally decompose in an extruder to produce gas, mainly CO ₂ and / or nitrogen, for example sodium bicarbonate, ammonium carbamate, azodicarbonamide or citric acid. Foaming agents that are completely converted into gaseous products, as well as their use in the form of a superconcentrate made on the basis of polyamide or wax, are preferred.

The production of the shell is carried out by extrusion. The thermoplastic mixture is simultaneously melted, plasticized and compacted in an extruder. Next, the melt is extruded through an annular die with the formation of a primary sleeve with relatively thick walls. Then the primary sleeve is rapidly cooled to fix the amorphous state of the polymers, after which it is reheated to the temperature necessary for orientation. The sleeve is simultaneously oriented in the longitudinal and transverse directions. Longitudinal tension is usually performed by means of two pairs of squeeze shafts with increasing drive speed; lateral tension is usually carried out under the influence of gas, which exerts pressure on the walls of the sleeve from the inside. The coefficient of surface tension (the product of the coefficient of tension in the longitudinal and transverse directions) is usually 6-18, preferably 8-11. After stretching, the sleeve is preferably thermofixed, cooled and wound.

This method of producing a foamed film, however, is associated with a high frequency of its breaks during orientation drawing, since the film contains only one layer, and the foaming agent is in a finely dispersed state and its particles can be close to the surface of the film. In this case, there is a high probability of the formation of open cells that can become sources of propagation of film rupture during orientation drawing. The probability of tearing is especially high if the film does not contain softening agents (elastomers) of the type specified above the copolymer. Meanwhile, such copolymers (elastomers), which make up a significant share in the film formulation, are quite expensive. It should be noted that the application text does not say anything about the appearance of this shell.

In connection with the foregoing objective of the present invention is to develop a technologically advanced and convenient method for producing a polymer shell for food products based on polyamide having a pseudo-fiber appearance that mimics the surface of a protein artificial shell.

Another objective of the present invention is the polyamide-based shell itself, having a pseudo-fibrous appearance that mimics the surface of a protein artificial shell.

Another objective of the present invention is the shell, which solves the above problem and at the same time has the desired (moderate) adhesion to minced meat.

Unexpectedly, it turned out that these problems are solved by the fact that in the manufacture of a sleeve shell in an extruder designed to produce an outer or single layer of the shell, a polymer composition is introduced containing:

98.5-73% by weight of the composition of the polyamide base;

1-25% by weight of the composition of the hydrophilic polymer, which forms a coarse dispersed phase when mixed with a polyamide base;

0.01-0.6% by weight of the composition of a liquid plasticizer of a hydrophilic polymer having a boiling point at normal pressure below the temperature of the melt at the exit of the extruder.

The indicated concentration range of the liquid plasticizer of the hydrophilic polymer refers to the entire set of low boiling plasticizers having a molar mass of 18 to 100 g / mol.

Since the effect of pseudo-fiber, and therefore the appearance of the shell, is determined by the volume of gas (vapor) released when the extrudate leaves the extruder die, and this volume is proportional to the molar content of the low boiling plasticizer in the hydrophilic polymer, when choosing suitable concentrations of a particular low boiling plasticizer, one should take into account its molar mass . It is also necessary to take into account the content in the composition of the hydrophilic polymer in which this plasticizer is concentrated.

When the content of liquid low-boiling plasticizer is below 0.0003 mol per 1 g of hydrophilic polymer, the effect of pseudo-fiber is not sufficiently pronounced, and above 0.0012, the process of manufacturing the shell is difficult due to frequent rupture of the shell during orientation drawing.

Thus, in the most general form, the criterion for choosing the molar content of a low boiling plasticizer is as follows:

,

,

where C _mol is the concentration of low-boiling plasticizer, expressed in the number of moles per 1 gram of hydrophilic polymer, equal to

,

,

where C _plast is the concentration of the low boiling plasticizer in the composition, expressed in wt.%, C _GP is the concentration of the hydrophilic polymer in the composition, expressed in wt.%, M _plast is the molar mass of the low boiling plasticizer, expressed in g / mol.

Thus, the optimal mass concentration of low-boiling plasticizer in the composition (%) is expressed as

,

,

wherein C _mole is selected in accordance with criterion (1).

A method for producing a sleeve polymer shell for food products includes the steps of extruding the polymer composition or coextruding it with other polymer layers (for a multilayer shell) through an annular die, cooling the extrudable sleeve, heating it to the temperature necessary for orientation drawing, orientation drawing using the bubble blowing method, followed by heat setting and reeling of the finished sleeve.

Moreover, the polyamide base contains at least one polyamide or copolyamide selected from the group consisting of polyamide 6, copolyamide 6.66, copolyamide 69, copolyamide 612, terpolyamide 6 / 66.9, terpolyamide 6 / 66.12, or a mixture thereof ;

the hydrophilic polymer is selected from the group consisting of starches, dextrins, ethers and esters of starches or mixtures thereof, and its content in the composition is preferably 4-10% by weight of the composition;

the hydrophilic polymer plasticizer is selected from the group consisting of water (100 ° C - hereinafter in parentheses the boiling point is indicated at normal pressure), ethylene glycol (197 ° C), 1,2-propylene glycol (187 ° C), monoethanolamine (170 ° C), dimethylformamide (154 ° С), dimethylacetamide (165 ° С), dimethyl sulfoxide (189 ° С). The plasticizer of the hydrophilic polymer can also be mixed.

The hydrophilic polymer can be introduced into the extruder in the form of a powder or granulate. However, the most preferred form is granulate, methods for which are well known from the prior art (see, for example, DE patent No. 4317696, publ. 12/22/1994).

The sleeve shell obtained by the above method contains a plurality of lenticular internal cavities up to 10 mm long in the direction of the sleeve axis and located at a distance of 0.5-2 mm in the direction perpendicular to the sleeve axis, which together create the illusion of fibrousity.

The sleeve shell can be made as single-layer or multi-layer.

The multilayer shell is made by the method of coextrusion, well known to specialists from the prior art, and contains additional inner layers made, for example, of polyolefins, modified polyolefins and polyamides. In this case, the layer providing the pseudo-fiber appearance is outside. This shell is mainly suitable for cooked sausages.

In a preferred embodiment, the shell, in addition to the low boiling plasticizer of the hydrophilic polymer, may additionally contain other plasticizers, including glycerin, monoglycerates, polyethylene glycol, sorbitol. In addition, it may contain fillers, such as chalk or talc, pigments, dyes, anti-blocking and / or processing aids (lubricants, etc.). The shell may also contain additives known from the prior art, providing its improved ability to pass aromatic substances of smoke and water vapor. So, in the patent of the Russian Federation No. 2182107 (publ. 10.05.2002) shells with increased vapor and smoke permeability are disclosed, which is due to the presence of a highly dispersed phase of hydrophilic compounds in a polyamide base, in particular polyvinyl alcohols with a hydrolysis degree of 68-90 molar percent and average molecular weight of 40,000-70000 and / or polyvinylpyrrolidones with an average molecular weight of 8000-15000. These additives in the amount of 3-50 wt.% Of the total mixture are able to form a highly dispersed phase in polyamide and provide the ability of the shell to smoke. In this case, the casing of the present invention contains one layer and is suitable for smoked sausages.

The hydrophilic polymers of the present invention — starches, dextrins, starch ethers and esters, or mixtures thereof — are capable of being mixed in the molten state with a polyamide, but are not soluble in its melt. Therefore, they form a coarsely dispersed phase with a particle size (domain) of mainly 5 to 50 microns.

The appearance of lenticular cavities imitating fibers is probably due to the sharp boiling of a plasticizer localized in the domains of a hydrophilic polymer dispersed in the polyamide melt and subsequent spunbond and orientation drawing, leading to stretching of the formed cavities. Since when dispersing the hydrophilic polymers of the present invention, their particles are wetted by the polyamide melt, the possibility of these particles reaching the surface of the film is excluded. This leads to the fact that the region of sharp expansion is localized in the central region of the cross section of the film and the resulting cells are closed. In addition, the plasticizer is a liquid at room temperature; upon cooling, it condenses in the cavities and is again absorbed by starch particles, therefore the formation of cavities of a different shape, except for lenticular, is excluded.

Using the proposed polymer composition allows you to get a cheaper polyamide shell in comparison with the prototype due to the fact that it does not include highly elastic copolymers (elastomers) containing blocks of polyamide and simple or complex aliphatic ether, which make up a significant proportion in the film formulation and are quite expensive .

The proposed method for the production of polyamide sausage casing in accordance with the present invention is high-tech and allows to minimize tearing of the casing during orientation drawing. This allows you to increase the productivity of the extrusion line and reduce the cost of the shell by reducing the amount of waste in its manufacture.

The creation of a shell with a pseudo-fiber appearance allows polymer shells to be similar in properties and appearance to protein artificial shells that have traditionally been used in the sausage industry and have an attractive appearance to the consumer.

In addition, it was found that the proposed shell has the desired adhesion to sausage meat. That is, the casing is adjacent to the sausage meat in such a way that during the production of sausages, no broth edema is formed, and when the casing is removed, the integrity of the surface of the sausage meat is not violated.

The mechanical properties of the casing comply with the requirements for sausage casings, including those requiring smoking.

The shell according to the invention can be made straight, curved or spiral, and its thickness is 20-50 microns.

The essence of the present invention is illustrated, but not limited to the following examples.

In the examples of implementation, the following material conventions were used (in parentheses are the brands of materials and manufacturers):

- PA 6.66 - (Ulramid C33, BASF).

- SK - Brown pigment superconcentrate in polyamide - (Sicopas 30-9705 С-35, BASF).

- Starch - Corn starch (Russia).

- Dextrin - Potato Dextrin (Russia).

Examples 1-6.

Single-layer shells of the general composition indicated in table 1 are made according to the following technology in two stages:

1. A mixture of hydrophilic polymer and glycerol is kneaded in an industrial cutter until a homogeneous mixture is formed and passed through a single-screw granulating extruder to obtain granulate. The temperature of the strands at the exit of the extruder is 130-150 ° C. Then the granulate is conditioned in a hygrostat until moisture is reached in accordance with Table 1.

Humidity was determined using the ISO 960D method on a METLER TOLEDO HR73 moisture analyzer.

2. The produced granulate and polyamide are kneaded in a “drunk barrel” type mixer for granular materials, loaded into an extruder and melted. The melt with a temperature of 200-220 ° C is fed into the annular head and form a primary sleeve with a diameter of 15 mm and a wall thickness of 158 microns. Then, at a temperature of 60-70 ° C, it is subjected to a biaxial orientation stretch blow molding with a longitudinal tensile coefficient of 2.6, transverse 3.0. After that, the air-inflated sleeve is subjected to relaxation annealing at a temperature of 150-160 ° C for 15 seconds, cooled to 20 ° C and wound into a roll.

The process went smoothly; shell ruptures during orientation were not observed.

The result is a shell having a diameter of 45 mm and a thickness of 19-21 microns.

Table 1. Example No. The composition, wt.% The moisture content of the granulate,% (water content mol / 1 g) Polyamide base Starch Dextrin Glycerol Water* PA 6.66 SC one 90 3 5 - 2 0,045 1 (≈0,0005) 2 90 3 5 - 2 0.0675 1.5 (≈0,00075) 3 89 four 5 - 2 0.09 2 (≈0.001) four 90.5 four - four 1,5 0,036 1 (≈0,0005) 5 90.5 four - four 1,5 0,054 1.5 (≈0,00075) 6 90.5 four - four 1,5 0,072 2 (≈0.001) * The data given in this column are calculated by the formula (3).

The appearance of the shell is described in table 2.

table 2 Example No. General view of the shell View under a magnifying glass one Pseudo-fiber Light longitudinal stripes 0.1-0.3 mm thick, up to 3 mm long (in the direction of the sleeve axis), spaced 1-2 mm apart in the direction perpendicular to the sleeve axis 2 Visible pseudo-fiber The same stripes, but up to 7 mm long 3 Pronounced pseudo-fiber The same stripes, but up to 10 mm long four As in example 1 As in example 1 5 As in example 2 As in example 2 6 As in example 3 As in example 3

The casings made were stuffed with sausage stuffing. Sausage loaves were cooked in accordance with the technology generally accepted for cooked sausages. Ready-made chilled sausages were tested for shell adhesion to minced meat. The results are shown in table 3.

Examples 7-8 (comparative)

A single-layer shell is made according to example 1 with a moisture content in starch (example 7) and dextrin (example 8) of 0.5% by weight (≈0,00025 mol / 1 g), which is 0.0225% of the total weight of the composition. The process went smoothly; shell ruptures during orientation were not observed. Both shells were slightly matte with no noticeable signs of pseudo-fiber.

Then in the shells prepared sausage as in examples 1-6.

Table 3. The shell according to example No. Behavior when removing shell from sausage one. Moderate adhesion. The shell was cleaned smoothly without tearing the meat from the surface of the sausage 2. Similarly 3. Similarly four. Similarly 5. Similarly 6. Similarly 7. (comparative) Strong adhesion. The shell was cleaned with cuts of minced meat from the surface of the sausage 8. (comparative) Similarly

Examples 9-10 (comparative)

They tried to produce a single-layer shell according to Example 1 with a moisture content of 2.5% by weight (≈0.0013 mol / 1 g), 0.113% of water by weight of the composition, respectively, in the content of starch and dextrin. The process was accompanied by constant rupture of the shell during orientational drawing.

Example 11 (comparative)

A single-layer shell is made according to stage 2 of the technology described in example 1-6, but without introducing hydrophilic polymers into the polyamide base. In this case, the polyamide is moistened in a hygrostat to a moisture content of 0.1% by weight. The process was accompanied by periodic ruptures of the shell during orientational drawing. The resulting shell contains lenticular cavities less than 1 mm long, which do not create an external pseudo-fibrous effect.

Example 12

A single-layer shell is made according to example 1 from the granulate obtained by mixing 5 weight. parts of starch, 2 weight. parts of glycerol and 0.35 weight. parts of 1,2-propylene glycol (≈0.001 mol / 1 g of starch), which is 0.38% of the total weight of the composition, without subsequent hygrostatation. As a result of a smooth extrusion process, which was not accompanied by ruptures, a shell with a noticeable pseudo-fiber was obtained, as in example 1.

Example 13 (comparative)

The single-layer shell is made according to example 1 from a polymer mixture of the following composition: PA 6.66 - 96.7 wt.%, SC - 3 wt.% And superconcentrate of blowing agent in polyethylene (Corducell ET 9520, NEMETZ Additive Plastic GmbH) - 0.3 wt.%.

The process was accompanied by frequent rupture of the shell during orientational drawing; moreover, primary sleeve ruptures periodically occurred immediately after extrusion. The resulting shell contained ellipsoidal cavities, manifested in the form of bright spots that did not create a pseudo-fiber appearance.

Claims (20)

1. A method of obtaining a sleeve of at least a single-layer polymer shell for food products, comprising the steps of (co) extruding the polymeric composition on a polyamide basis through an annular die, cooling the extrudable sleeve, and then heating it to the temperature necessary for the orientation drawing, which is carried out by the method bubble blowing, heat setting and winding of the finished sleeve, characterized in that a polymer composition is introduced into the extruder for the outer layer of the shell, consisting of: 98.5-73% by weight of the composition polyamide base; 1-25% by weight of the composition of the hydrophilic polymer, which forms a coarse dispersed phase when mixed with a polyamide base; 0.01-0.6% by weight of the composition of a liquid plasticizer of a hydrophilic polymer having a boiling point at normal pressure below the temperature of the melt at the exit of the extruder. 2. The method of producing a shell according to claim 1, characterized in that the polyamide base contains at least one polyamide or copolyamide selected from the group consisting of polyamide 6, copolyamide 6.66, copolyamide 69, copolyamide 612, terpolyamide 6/66 9, terpolyamide 6 / 66,12 or a mixture thereof. 3. The method of producing a shell according to claim 1, characterized in that the hydrophilic polymer is selected from the group consisting of starches, dextrins, ethers and esters of starches or mixtures thereof. 4. The method of producing a shell according to claim 1, characterized in that the liquid plasticizer is selected from the group comprising water, ethylene glycol, 1,2-propylene glycol, monoethanolamine, dimethylformamide, dimethylacetamide and dimethyl sulfoxide. 5. The method of producing the shell according to claim 1, characterized in that the polymer composition further comprises at least one plasticizer, with a boiling point at normal pressure above the melt temperature at the exit of the extruder. 6. The method of producing a shell according to claim 1, characterized in that the polymer composition further comprises at least one additive selected from pigments, dyes, fillers, anti-blocking and / or processing additives. 7. The method of producing the shell according to claim 1, characterized in that the hydrophilic polymer is preferably introduced into the extruder in granular form. 8. Sleeve, at least one-layer polymer shell for food, made by the method according to claims 1 to 7. 9. The sleeve shell of claim 8, characterized in that it contains lenticular cavities 3-10 mm long in the direction of the axis of the sleeve. 10. The sleeve shell according to claim 9, characterized in that the cavity is located at a distance of 0.5-2 mm in the direction perpendicular to the axis of the sleeve. 11. The sleeve casing of claim 8, characterized in that it further comprises at least one additive that provides the ability of the casing to pass aromatic substances of smoke and water vapor. 12. The sleeve casing of claim 8, characterized in that it is multilayer. 13. The sleeve shell according to item 12, wherein the outer layer contains lenticular cavities 3-10 mm long in the direction of the axis of the sleeve, located at a distance of 0.5-2 mm in the direction perpendicular to the axis of the sleeve. 14. The sleeve shell according to item 13, characterized in that it contains other layers connected to the outer layer. 15. The sleeve shell according to 14, characterized in that it contains at least one layer made of a polyolefin thermoplastic material. 16. The sleeve shell according to 14, characterized in that it contains at least one layer made of polyamide thermoplastic material. 17. The sleeve shell according to 14, characterized in that it contains at least one layer containing a modified polyolefin having improved adhesion to the polyamide. 18. The sleeve shell according to claim 17, wherein the modified polyolefin is a polyolefin modified by grafting at least one unsaturated compound selected from the group consisting of unsaturated carboxylic acids, cyclic unsaturated dicarboxylic acid anhydrides. 19. The sleeve casing of claim 8, characterized in that the film thickness is 20-50 microns. 20. The sleeve casing of claim 8, characterized in that it is made straight, curved or spiral.