WO2001003508A1

WO2001003508A1 - Slip resistant food casing and method for making same

Info

Publication number: WO2001003508A1
Application number: PCT/GB2000/002651
Authority: WO
Inventors: Ronald Sherwood Kearby; Garry Rundblom
Original assignee: Teepak Investments, Inc.
Priority date: 1999-07-12
Filing date: 2000-07-10
Publication date: 2001-01-18
Also published as: AU5996600A

Abstract

A tubular food casing having an exterior coating thereon, where the coating includes a mixture of a food compatible resin and inorganic particles. The particles generally have a particle size of from about 0.1 to about 25 microns. The weight ratio of resin to inorganic particles is usually from about 0.2:1 to about 4:1. A preferred inorganic particle is silica that may be colloidal silica. Preferred resins are cationic, food compatible resins. The casing preferably has a weight ratio of coating to casing of from about 0.001:1 to about 0.1:1.

Description

SLIP RESISTANT FOOD CASING AND METHOD FOR MAKING SAME

This invention relates to food casings and more particularly relates to tubular food casings that are suitable for use on high speed food stuffing equipment. Such food casings may be of essentially any film material but are most usually made of cellulose film material that may be either fiber reinforced or unreinforced. Such food casings may also be of other film materials e.g. collagen or plastic such as polyethylene or polypropylene. When the material is cellulose it may be cellulose regenerated from a cellulose derivative such as xanthate viscose or may be underivatized cellulose precipitated from a cellulose solution, e.g. tertiary amine oxide solution or cupraammonium solution. A problem associated with such food casings, e.g. as described in U.S. Patent 4,967,798, is that when such casings are loaded onto a stuffing horn of a machine that stuffs food into the casing, such casings are very difficult to grip. The lack of grip arises for a number of reasons. The casings themselves are made of a film forming material that has a smooth surface. Further, such casings are often moisturized (typically with glycerine) which adds a certain lubricity to the casing surface. This is further aggravated by the fact that plasticizers and lubricants are often present that add even further to slipperiness of the casing surface.

U.S. Patent 4,967,798 attempted to solve the problem by coating the outside surface of the casing with particles or fibers of cellulose or a synthetic resin to provide a ^"roughened^" outer surface. While the method used in U.S.

Patent 4,967,798, no doubt has some effect, the surface of the casing of U.S. Patent 4,967,798, still does not provide as much ^"grip^" as desired to the outside surface of the casing. In addition, ^"grip^" may become worse after the casing is soaked in warm water (120°F) .

Brief Description of the Drawings Figure 1 shows a perspective view of a section of an embodiment of a food casing of the invention. Figure 2 shows a magnified cross sectional view of the coated film used in the food casing of Figure 1.

Brief Description of the Invention In accordance with the invention, a tubular food casing is provided having an exterior coating thereon, where the coating includes a mixture of a food compatible resin and inorganic particles that solves problems associated with prior casings.

The weight ratio of resin to particles is in the range of about 0.2:1 to about 4:1 and the inorganic particles have a particle size of from about 0.1 to about 25 microns, and preferably 0.1 to about 10 microns, to increase grip and reduce slip.

In particular, it has been discovered that there is a preferred and unobvious concentration range and resin to particle ratio that permits increased grip while reducing the required quantity of inorganic particles with resulting reduction in cost, reduction in casing stiffness and reduced change in the natural color of the casing. In this case, the particles generally have a particle size of from about 0.1 to about 10 microns and preferably from about 0.25 to about 5 microns. The weight ratio of resin to inorganic particles may be from about 0.5:1 to about 2:1 or even to about 4:1 but is preferably from about 0.5:1 to about 2:1 and even more preferably is from about 0.25:1 to about 1.5:1. The preferred weight ratio of resin to particles is from about 0.5:1 to about 4:1, more particularly from about 0.5:1 to about 2:1, and the most preferred weight ratio is from about 0.5:1 to about 1:1.

A preferred inorganic particle is silica that may be colloidal (fumed) silica. Preferred resins are cationic, food compatible resins. The casing preferably has a weight ratio of coating to casing of from about 0.001:1 to about 0.1:1, more particularly from about 0.01:1 to about 0.1:1 and the most preferred weight ratio is from about 0.001:1 to about 0.05:1. The coating thickness on the casing is usually from about 1 to about 25 microns, preferably from about 1 or 2 microns up to about 10 microns and usually comprises no more than 30 percent, conveniently no more than about 15 percent, desirably no more than 5 percent and most preferably no more than 1 percent of the entire thickness of the casing. The solid coating add-on is usually from about 50 to about 400 milligrams per square meter of casing. The invention also includes a method for making the food casing which includes coating the exterior of a tubular film with an aqueous suspension containing from about 0.2 to about 10 weight percent, desirably 0.2 to about 5 weight percent, and most preferably from about 0.25 to about 1.5 weight percent water insoluble inorganic particles. The particles have an average particle size of from about 0.1 to about 25 microns, but preferably from about 0.1 to about 10 microns. The suspension also contains from about 0.2 to about 10 weight percent of a food compatible resin, 5 weight percent, and preferably from about 0.3 to about 2.5 weight, percent of a food compatible resin. The weight ratio of resin to inorganic particles (silica) in the suspension may be from about 0.2:1 to about 1.5:1 for particle concentrations of less than 2 weight percent in the coating suspension, but is preferably from about 0.5:1 to about 1:1. These weight ratios have been unexpectedly found to result in optimum grip at relatively low particle and resin concentrations. The casing is usually a cellulose food casing and the coating in a preferred embodiment is done by running the casing through a tank containing the aqueous suspension followed by drying the casing. Detailed Description of the Invention The particles used in accordance with the invention are water insoluble inorganic particles desirably having sharp edges formed either by fracture or by crystal growth, e.g. abrasive grit. Such inorganic particles may, for example be particles of glass, silica, alumina, titania, calcium carbonate, or water insoluble silicates. Such materials are believed to impart superior non-slip characteristics to the outside surface of food casings because they tend to have sharp edges that are better able to grip or grab into softer materials than can softer and usually more rounded cellulose or resin particles as described in U.S. Patent 4,967,798.

The resin is preferably a cationic resin that may be a condensation polymer of an aldehyde, e.g. the condensation product of formaldehyde, malonaldehyde, or glyoxal with a protein, urea, or melamine. Other desirable cationic resins are condensation products of epichlorohydrin with a polyamine, polyamide or polyaminepolyamide . An example of such a resin is the

KYMENE resin of Hercules Incorporated that is an aqueous solution of polyamide-epichlorohydrin resin at a concentration of about 12.5 percent solids. Other similar suitable resins are the RESAMINE resins from Cassella. The resins may be precured when they are added to the suspension; provided that, they form contiguous films on the casing surface to firmly hold the particles. The resins may also be uncured or partially cured in the suspension and then cured later after excess liquid is removed from the surface of the casing, e.g. by drying.

Resins other than cationic resins can also be used, e.g. cellulose can be used as the binding resin by mixing the particle into viscose, extruding the mixture as an outside layer onto the casing and regenerating the cellulose. The same effect can be obtained by mixing the particles into a solution of cellulose in water and tertiary amine oxide. The suspension used to coat the surface of the casing is usually a suspension of the inorganic particles in an aqueous solution of resin. The pH of the suspension is preferably from about 4 to about 7. This pH range usually optimizes the coating characteristics.

"Tubular food casing^" referred to herein is usually a flexible tubular film having a thickness of from about 0.02 to about 0.2 millimeters and a dry flat width of from about one centimeter to about 15 centimeters. The food casing is usually cellulose, collagen or plastic that may be unreinforced or may be reinforced, e.g. with fibres such as cellulose fibres in the form of a paper mat. When the casing is cellulose it may be cellulose regenerated from a derivatized cellulose, e.g. xanthate viscose or may be cellulose precipitated from a solution of non-derivatized cellulose, e.g. from a solution of cellulose in a mixture of tertiary amine oxide and water.

^"Exterior^" or ^"outside^" as used herein means that surface of the casing which in general is not intended to be placed in contact with contained food, e.g. the outside cylindrical surface of an inflated tubular food casing.

^"Coating^" means a covering on the outside surface of a mixture of the particles and the resin no matter how the coating is obtained. It may for example be obtained by passing the casing through a bath containing a suspension of the resin and the particles or it may be coextruded onto the outside surface of the casing.

^"Food compatible resin^", as used herein, means that the resin, if ingested in minor amounts will cause no harm and that the resin will not cause undesirable degradation of food product if placed in contact with the food.

The tubular food casing of the invention may be further illustrated by reference to the drawings illustrating a preferred embodiment. For purposes of illustration, the cross section of the film forming the casing is magnified many times relative to the diameter of the casing. It is to be understood that the drawings are for the purpose of illustrating and not limiting the invention .

As seen in Figure 1, tubular food casing 10 is made from a film 12 having an outside surface 14 with coating 16 thereon. Coating 16 holds inorganic particles 18 onto surface 14 to increase the ease of gripping the casing. Figure 2 shows a cross section of a portion of the coated film of Figure 1 wherein film 12, coating 16 and particles 18 are more easily seen. It can be readily seen that the particles have sharp or pointed edges that decrease slipperiness of the film and increase grip.

The following examples serve to illustrate and not limit the present invention.

A fiber reinforced cellulose food casing having a flat width diameter of between about 70 and 76mm. (Industry code 1MR) was run through a dip tank containing an aqueous suspension having the characteristics shown in Tables I and

II. The temperature of the suspension was maintained between 40 and 50 degrees Celsius. The resin used in the examples was Hercules KYMENE resin 4190 (12% solids) pH 4.6 to 4.9 and the silica used was H.B. Fuller FULL-GRIP amorphous silica WB-4722 (20.25% solids) pH 10. An example of formulation make-up for an aqueous suspension having 1% silica and 1% resin solution is:

Soft water 12.1 gallons

Silica WB-4722 0.8 gallons

Resin 4190 1.3 gallons

Glycerin 1.8 gallons

Total 16.0 gallons

Other formulations are appropriately adjusted to obtain the concentrations shown in Tables I and II.

To prepare the aqueous suspension the soft water was added to a heater-equipped mixing tank. The heater temperature was set to 45°C and the glycerin was added and mixed for 5 minutes (the glycerin was used in the tank to prevent loss of glycerin from the cellulose food casings to be tested) . The silica solution was then slowly added and mixed until well dispersed (about 15 minutes) . Resin was then added and again mixed until well dispersed and until the temperature reached between 40 and 50°C. The mixed formula was then added to a circulating dip tank and the temperature maintained between 40 and 50°C. The level of the dip tank was maintained automatically from the mixing tank.

Fibrous casing from the manufacturing process machine was passed through the dip tank containing the appropriate formulation and dried to form the coated casing.

In a first series of test results as set forth in Table I Examples 1 to 6 were evaluated.

For purposes of comparison the inside surface of the casing in examples 5 and 6 was also coated with resin and silica using a slug of liquid containing colloidal silica (inside silica cone.) . The coated casings were tested and it was found that

Examples 1, 3 and 6 coated with the silica-resin coating without the glycerin had surface friction about the same as similarly coated examples where the casing contained glycerin. One benefit of the glycerin (Examples 2, 4 and 5) was that dusting was significantly reduced during a string tie operation during stuffing; although, the casings were still undesirably stiff and hard to stuff.

Example 5 with only Kymene on the outside improved the outside surface friction over a control made the same way without Kymene, but slippage occurred during a pull test, and was not as good as Examples 1, 2, 3, 4 and 6 all of which contain silica. Example 6 with silica on the inside improves the ease of grip to open the casing compared to the control, but is no better than Example 4, which is simpler to manufacture.

In a second series of test results as set forth in Table II Examples 7 to 14 were evaluated. Examples 9 and 10 with one percent silica and four and two percent resm respectively (ratio of 2:1 and 4:1 resm to silica respectively) had more slip than desired causing clip slippage during stuffing and greasing out after stuffing (forming grease pockets against the casing surface) .

Examples 11 through 14 illustrate the importance of a resm to silica ratio of 1.5:1 or less. At these lower ratios low concentrations of both resm and silica can be used with good grip , dramatically reduced casing stiffness and good color. Optimum ratio at one percent silica concentration appears to be about 1:1. Example 14 at a relatively high coating suspension pH of 8.5 is not as good as example 13 which is identical except for the lower 5-6pH of the coating suspension.

TABLE I

TABLE II

Claims

Claims :

1. A tubular food casing having an exterior coating thereon, which coating comprises a mixture of a food compatible resin and inorganic particles having a particle size of from about 0.1 to about 25 microns, the weight ratio of resin to inorganic particles being in the range 0.2:1 to about 4:1.

2. The food casing of claim 1, wherein the particle size of the inorganic particles is in the range 0.1 to 10 microns.

3. The food casing of either preceding claim, wherein the weight ratio of resin to inorganic particles is in the range 0.2:1 to 1.5:1.

4. The food casing of claims 1 or 2 , wherein the weight ratio of resin to inorganic particles is in the range

0.5:1 to 1:1.

5. The food casing of any preceding claim, wherein the coating thickness is in the range 1 to 25 microns.

6. The food casing of claim 5, wherein the coating thickness is in the range 1 to 10 microns.

7. The food casing of any preceding claim, wherein the weight ratio of coating to casing is in the range 0.1:1 to 0.001:1.

8. The food casing of claim 7, wherein the weight ratio of coating to casing is in the range 0.05:1 to 0.001:1.

9. The food casing of any preceding claim wherein the inorganic particles are silica particles.

10. The food casing of Claim 9 wherein the inorganic particles are in the form of colloidal silica.

11. The food casing of any proceeding claim wherein the resin is a cationic resin.

12. The food casing of Claim 11 wherein the resin comprises an epichlorohydrin resin.

13. A method for making a food casing which comprises coating the exterior of a tubular film with an aqueous suspension containing from about 0.2 to about 10 weight percent water insoluble inorganic particles having a particle size of from about 0.1 to about 25 microns and from about 2 to about 10 weight percent of a food compatible resin.

14. The method of Claim 13 wherein the particles are present in the suspension in an amount of from about 3 to about 7 weight percent and the weight ratio of resin to silica is from about 0.5:1 to about 4:1.

15. The method of claim 13, wherein the particles are present in the suspension in an amount of 0.2 to about 5 weight percent and the weight percent of resin is less than 7 and the suspension has a pH of from about 4 to about 7.