CA1081531A - Method of preparing collagen structures - Google Patents

Abstract

IMPROVED METHOD OF PREPARING
COLLAGEN STRUCTURES

ABSTRACT OF THE DISCLOSURE

An improved method of preparing shaped collagen structures is provided wherein a shaped collagen structure such as a tubular food casing is treated with a dewatering solution comprising at least about 0.01% by weight of sodium alginate prior to the drying thereof.

S P E C I F I C A T I O N

Description

-` 1013~531 The present invention relates to a method for producing formed collagen structures and more particularly to an improved method for preparing collagen products such as tubular food casings w~lerein a dewatering agent is used to treat the collagen structure before the final drying step.
For a number of years, products prepared from processed animal collagen in tubular, film, and strand ~orm have been manufactured and used in commercial quantities.
Collagen products generally obtained by the extrusion of ~ormable compositions into tubular structures have been used as ~ood casings in the processing of food products such as pork sausages and the like.
In the manufacture of collagen products such as tubular food casings, a typical process involves extrusion of a continuous length of collagen material that is gen- -;
erally conveyed through a series of liquid treatment baths including a plasticizing bath, and then dried and sized, generally by hot alr means. The dried tubing may be sub-sequently shirred and compressed to obtain short lengths -thereof, commonly called shirred casing sticks. For example, in U.S. Patent Nos. 3,123,482 and 3,413,129 to Lieberma~; U.S. Patent Nos. 3,123,4~3 and 3,235,641 to ~IcKnight; and U.S. Patent No. 3,446,~33 to Talty are dis-closed various processes that may be used in the prepara-tion of collagen tubing from low collagen solids composi-tions and, alternatively, in U.S. Patent Nos. 3,551,535 and 3,782,977 to Henderson et al are disclosed processes that ma~ ~e`employed in the preparation of such tubing from collagen compos~it~on having high collagen solids content.

2, ~08153~

Drying of the processed collagen tubing before storage and/or shirring is an essential and key step which is usually carried out in hot air driers with the tubing in an inflated condition, The equipment employed is expensive, requiring a substantial capital investment, and drier capacity generally determines maximum production line speed. Hereto-fore, methods other than hot air drying have been suggested for the removal of water during the preparation of various types of collagen products, among which are, for example, freezing, (U.S. Patent No. 3,136,682); tanning agents, (U.S.
Patent Nos. 2,246,236, 2,750,251 and 3,223,551); dialysis and pressure, ~U.S, Patent No, 2,~38,363~; and pH adjustment, (U.S.
P~tent ~o, 3,223,551?, Treatments postulated to remove water by pH adjustment (U.S. Patent No. 3,223,551) involve distilled water extraction, ~U.S. Patent No, 2,838,363); ketone and alcohol extraction, (U.S. Patent Nos. 2,115,648, 2,934,447,

3,408,gl6 and 3,622,353); and buffer salts. It has also been disclosed, for example, in U.S. Patent No. 3,346,402 to Lieberman, that the addition of carboxymethyl cellulose to the aqueous glycerol bath generally used as a plastic-ization treatment for tubular collagen casings prior to drying, 'nas the effect of reducing the moisture content in the collagen tubing.
The need still exists, however, for the develop-ment of even further improvements in the processing of collagen products such as tubular food casings, sheet, strands and the li~e, particularly when such iMprovements realize a reduction in cost or time without adversely affecting other aspects of the process or properties of the produc~s produced thereby.

` 9744 ~08~53~

In accordance with the present invention, it has been discovered that when collagen containing structures are treated with relatively small amounts of the sodium salt of alginic acid, preferably in the form of an aqueous solution, prior to tlle drying thereof, water will be partially withdra~n from the collagen structure. This dewatering effect can be used to reduce the moistùre content of the collagen structure entering the drying equipmen~ thereby reducing the requirements therefor with a resultant reduc-~tion in the cost of such equipment or permitting an increase in t.~e process line production speed.
Collagen structures that may be treated can be prepared by any o the methods known in the art using collagen tissues obtained from a variety of raw materials as, for example, limed and unlimed animal hide splits and tendon.
Sodium alginates, which are sodium salts of alginic acid, are known materials available commercially in various viscosity grades. Thus, for example, various viscosity grades of sodium alginates are available from ~'~ the Kelco Company under the trade designations KELCOGEL
and KELGIN.
Dewatering shaped collagen structures in accordance with the present invention can be accomplished ;
by using any one of a number of methods for applying a sodium alginate dewatering agent, preferably in the form of an aqueous solution, to a surface of the wet collagen structure. Thus, for example, the collagen structure may be passed t'nrough a dip treatment bath comprising an aqueous solution of sodium alginate in concentrations to be more fully discussed hereinafter prior to advancing to the drying chamber~ A preferred and particularly advantageous ~ 4 ` 9744 108153~

method comprises passing a collagen structure through anaqueous dip treatment bath,' such as the aqueous glycerol plasticizing bath that is generally employed in the processing of collagen structures such as tubular food casings, and in which has also bëen incorporated the amount herein described of sodium alginate dewatering agent, Aqueous dewatering solutions suitable for use in accordance with the practice of the invention comprise at least about 0.01% and preferably at least about 0.5%
by weight of sodium alginate. The concentration of sodium alginate'can vary over a wide'range and the upper limit is not critical being determined generally by economic considera-tions or such other factors as, for example, the viscosity of the solution, the composition of the bath and whether it is also used to concurrently provide other forms of treatment for the collagen structure, ~he process line ' speed that is desired, and the like. However, sodium `
alginate concentrations greatly in excess of about 10%
by weight may unduly increase the viscosity of the solution -~
and/or blocking tendencies of collagen tubing and con-centrations in excess of about 4% by weight is not gen-erally needed to impart the desired dewatering of collagen structures.
Suitable dewatering treatment solutions of the present invention may also contain other ingredients and preferred embodiments thereof may be prepared with any one of the polyols known in the art as being suitable for use as a plasticizer for various collagen structures. The concentration of such polyol plasticizer component in the aqueous treatment solution generally depends on the con-:16)8~S3~

centration generally required for plasticization of the collagen structure. For example, if a polyol plasticizer such as glycerol is to be used, t~e concentration thereof should be about 2% by weight up to about 30~/O by weight and preferably up to about 10% by weight The pH of the dewatering treatment solution is important, it being essential that the pH of the bath is maintained at a level where the collagen ma~erial does not swell. The pH of the treatment bath should therefore be maintained within the range o~ a pH about 4 to about a pH of 10, The temperature of the dewatering bath is also important and should generally be above the freezing point of the solution but below 40C, the temperature at which thermal degradation of collagen may occur. Preferably, the temperature of the bath should be maintained at a temperature below about 25C to inhibit microbial spoilage of the dewatering solution.
The viscosity of a dewatering treatment bath may be varied over a wide range and the upper and lower viscosity limits therefore are not critical. However, ~hen processing collagen articles such as tubular food casings it is generally desired that the bath viscosity be maintained as low as possible to enable the ready advance therethrough of the collagen tubing. In general, the viscosity of the dewatering treatment bath can be about 1 cp up to about 4000 cp and preferably up to about 10 cp.
In accordance with the practice of the invention>
dewatering treatment times may range from about 3 seconds to about 60 minutes and preferably from about one to about ~081~3~

ten minutes. When a combined dewatering and plasticizing bath is employed, the time generally required for the plasticizing trea~ment of a collagen structure such as a tubular food casing, e.gO between about 3 and 7 minutes, may be advantageously employed for the dewatering of such structure.
Exemplary of a preferred method of preparing a shaped collagen structure such as, for example, a tubular food casing, a collagen composition prepared as disclosed in U.S. Patent ~lo. 3,782,977 to Henderson et al, comprising at least about 6% by weight of collagen solids and having uniformly incorporated therein between about 5% and 30%
by weight of non-collageneous fibers based on the weight of total dry solids, is pumped and metered through an extrusion nozzle to form a continuous tube of collagen, which tube is strong enough to support itself in a tubular configuration with a low pressure inflation air while being conveyed to and through a predryer. The partially dried collagen tubing is then collapsed between nip rolls, neutralized by passing through a dip tank containing very dilute ammonium hydroxide, washed by pass-ing through water tanks, and then plasticized by being con-veyed through a dilute aqueous glycerine solution. In accordance with the practice of the invention, the aqueous plasticization bath has incorporated therein a sodium alginate dewatering agent in an amount as herein described.
It has been found that wherein collagen tubing that has been conveyed through a glycerine plasticizer bath will generally have a moisture content of between about 75% by weight to about ~5% by weight, the water content of collagen tubing conveyed through a plasticizer bath containing a proportion of sodium alginate dewatering agent in accordance with the practice of the invention will have a significantl~ lower moisture content, generally between about 55% to 67%.
The collagen tubing is then reinflated with low pressure air while maintaining the tubular configuration.
If desired, the dried tubing may then be shirred into a shirred casing stick using methods well known in the art, or alternatively wound on a reel in flattened condition.
It has been found that when employing a sodium alginate dewatering treatment in accordance with the prac-tice of the invention the line speed for processing collagen tubing including the drying thereof may be substantially increased without any change in drier capacity. For exam-ple, wherein a line speed for processing collagen tubing may be generally run at about 13.5 feet per minute~ such tubing processed as herein described using an aqueous solution of sodium alginate as a dewatering treatment may be processed using the same equipment at a line speed of 18 feet per minute, or even faster.
Collagen tubing prepared in the manner herein described perform satisfactorily through each of the various processing steps with, in general, no problems being encountered. I~oreover, it has been found that tubular collagen casings prepared in accordance with the practice of the invention, perform satisfactorily during shirring, stuffing, linking, and cooking operations.
Although, as shown ~erein, the use of sodium alginate in an aqueous solution serves as a dewatering agent for shaped collagen structures in the practice of the invention, the surprising fact is that products pre-- ': ' ..- : . . :.
." ' ': ' " ' ''`........ ~

53~

pared ~rom collagen compositions containing sodium alginate as an additive do not afford similar dewatering e~fects. It is known, as for example disclosed in U.S. Patent Nos.
3,551,535 to Henderson et al and 3,695,902 to Shank, t~at salts of alginic acid may be used an an additive in pre-paring collagen compositions from whic~ products such as tubular food casings ma~ be prepared. Yet, if such products are processed using the conventional treatment solutions, the moisture content thereof will not be any lower than found with products prepared from compositions that do not contain sodium alginate, and the drying requirements therefore are not reducedO
The following examples are set forth as illustrat-ing embodiments of the present invention and are not intended in any way to indicate the limits of the invention. Parts and percentages, unless otherwise indicated, are by weight.
The term "wt %" as employed herein is intended to refer to weight percent.
In the examples which follow, dewatering was measured by weighing the collagen article before and after treatment with the dewatering agents. A "dewatering index"
is used to rank dewatering efficiency which is defined as 100 times the collagen article weight after treatment divided by the collagen article weight before treatment.
A low value for the "dewatering index" indicates effective dewatering, a "dewatering index" of 100 indicates no dewater-ing, and an "index" greater than 100 indicates swelling rather than dewatering.

- 97~4 EgAMPLE I

1630 pounds of limed beef hide splits were chopped into approximateI~ 1/2~' to 2" pieces and subjected to an additional lime treatment by charging into a tank together with 57 pounds of lime and sufficient water to give a water to hide ratio of 3.9 to 1. The lime ~reatment was continued for 24 hours with intermittent agitation after which the limed hide chips were leached with approximately 10 gallons per minute of water for 20 hours.- The hide chips were then swollen for 8 hours in a hydrochloric acid solution main-tained at a pH of 1 using a flow rate of dilute acid of 10 galstmin. At the end of the acid swell treatment, the swollen chips were washed with water at 10 gals/min for about 5 hours until a wash water pH of 2.6 was reached. The chips were drained and c~illed to about 1C.
A cellulose fiber dispersion was prepared using the following ingredients:
Collagen-composition 254 pounds Wood Cellulose Fibers 155 pounds Water 2186 pounds The wood cellulose fibers used had an average fiber length of about 0.04". Sheets of fibers were separated into convenient pieces, soaked in a portion of the water for about 60 minutes and then mixed for about two minutes, soaked or an additional 30 minutes~ and then mixed for about two minutes, The rest of the ingredients were added to the mixer and the mixture was blended for about 165 minutes. The resulting wood celluLose fiber suspension was smooth, highly viscous, free of fiber clumps and had a composition of hide solids 1%, wood cellulose fibers 5.6% and water 93.4%.

~ 8153~

A 210 pound collagen composition having a total solids of 11.1% was prepared having t~e following proportion of solid ingredients:
Ground hide 85%
Wood Cellulose Fibers 15%
Acid-swollen chips prepared as described above were ground in a meat grinder into pieces substantially between 1/8" and 1/2" in si7e prior to blending with the vis-cous cellulose fiber dispersion. The temperature during ~rinding o tl~e c~ips was controlled so as not to exceed about 20C
The collagen composition was prepared by mixing 62 7 pou~ds of cellulose fiber dispersion, 126 pounds of ground acid-swollen chips having a solids content of 15.2%, and 21.1 pounds o water. The mixture was mixed for about five minu~es at which time the composition was homogeneous and began to adhere to the mixing equipment. The temperature of the various materials during the mixing steps was con-trolled so as not to exceed 20C.
Ater preparing the collagen composition, it was fed through a rotary-shear homogenizer by means of a screw extruder and pump. To prevent degradation of the collagen, the homogenizer rotor and stator were cooled with a coolant maintained at a temperature of about -5 C.
The homogenized blend was pumped through two parallel ~ilters with .003" slots to break up any remaining collagen lumps and remove any nondispersed matter, and then was pumped and metered through an extrusion nozzle to form a continuous tube of collagen. The extruded tubing was inflated with low-pressure in1ation air while being conveyed on horizontal rolls.

11 ~

,.",. . . .
, ~

~ 8 ~ S 3~
The inflated collagen tubing was partially dried and hardened by passing through a predryer at 50C, then collapsed between nip rolls, neutralized by passing through a dip tank containing 0,06 N ammonium hydroxide, and washed by being conveyed through water tanks. After washing, the collapsed collagen tubing was conveyed through an aqueous plasticizer treatment bat~ con~aining 4.5% glycerol. Two lengths of the flattened tubing were treated by conveying through a glycerol bath to which 1% or 2% sodium alginate had been added. The sodiurn alginate used in this example was KELGIN RL; a product of KeIco Co., San Diego, California.
The tubing samples were then reinfla~ed with low pressure air, dried in air at 100C, moisturized in an equalizer at 70% RH and then shirred by passing through a shirring apparatus.
Prior to reinflating and drying, samples of the advancing collapsed tubing from each of the glycerol trea~-ment baths were collected for two minutes and weighed and the results are shown in Table I. It will be noted from the tubing weights reported in Table I that the weight of the collapsed tubing treated in glycerol baths containing sodium alginate was less than that of the collapsed tubing that did not receive the sodium alginate treatment.
Observations were also made during drying of the infl2ted tubing. On drying completely, the casing changed from a milky opalescence to a clear translucence and the drier location where this transition occurred is also reported in Table I. Reinflated tubing samples that had been treated with sodium alginate were completely dried in a shorter length of drier than was the tubing that did not receive a sodium algina~e treatment.

r~ ~ r~4 12.

108~S3~

T~BLE I

Collapsed Sodium Alginate Tubing Weight Length Of Drier Casing TreatmentCGram~ Per 2Required For Drying Sample (% W/~) Minutes~ (Feet) A 0 109,5 26 B 1.0 85.9 19 C 2.0 69.0 16.5 EXAMPL~ II
_. .
Using the procedure of Example I, ground acid-swollen chips were prepared with the following differences:
hide weight 1741 pounds, lime weight 122 pounds, wa~er to hide ratio 3.6 to 1, lime time 57 hours, leach 9 hours at lOgpm water flow, wash 5 hours at lOgpm water flow.
A cellulose fiber dispersion was prepared as described in Example I. The resulting fiber dispersion was smooth, highly viscous, free of cellulose fiber clumps, and had a composition of collagen solids 1%, wood cellulose ibers 5.6%, and water 93.4%.
A 139 pound collagen composition was prepared as described in Example I by mixing 100 pounds of 12.7% ground acid-swollen chips and 39 pounds of cellulose fiber disper-sion.
After preparing the collagen composition, collagen tubing was prepared and treated in dip baths as described in Example I with the final dip bath containing 4.5% glycerol and optionally 0% or 1% sodium alginate. The casing line speed was 13.5 feet per minute when the final dip bath did not contain sodium alginate and 18 feet per minute with 1%
sodium alginate added to the final dip bath The sodium alginate used in this example was KELGIN RL, a product of Kelco Co.

13.

~L08~531 The tub;ng samples were then reinflated, dried, moisturized and s~irred as described in Example I. As des-cribed in Example I, samples of collapsed tubing conveyed from the glycerol treatmen~ bat~ were collected and weighed and the results are reported in Table II. Drying observa-tions were also made and the results are sho~m in Table II.

TABLE II

Sodium Alginate Length Of Drier In Final Bath Line Speed Collapsed Tubing Required For Sam~le ~% W/W~ (FPM) Weight (gms/2 min) Drying (Feet~
A 0 13.5 73.3 27 B 1.0 18 61.4 27 The results show that sodium alginate removed water from collapsed collagen tubing thereby permitting dry-ing of reinflated tubing in 27 feet of drier at a faster line speed than was possible without the sodium alginate treatment, EXAMPLE III

This example shows the effectiveness of aqueous treatment baths containing varying concentrations of sodium alginate.
Flattened collagen tubing prepared as described in Example I is collected after the final washing step and stored in frozen condition. Samples of thawed flattened tubing weighing about 10 gms are blotted thoroughly with a cloth towel to remove surface water and then weighed to the nearest 0.01 gms. Each of the samples of weighed tubing is treated for five minutes with agitation in an aqueous dip bath con~aining sodium alginate, the dip ba~hs being prepared with various concentrations of the sodium alginate.

:1081S~l The treated, flattened collagen tubing samples are then blotted and weighed. From the two weights, a "dewatering index" is calculated ~hich e~uals 100 times the weight after treatment divided b~ the weight before treatment. The lower the "dewatering index", the more effective is the dewater-ing treatment. A summary of the results of this example are reported in Table III.
The sodium alginate materials used in this example are KELCOGEL LV, KELGIN RL, AND KELGIN XL, all of w~ich are products of the Kelco Co. KELCOGEL LV is an especially-clarified, low-calcium, low viscosity grade of sodium alginate; KELGI~ RL is a refined, spec al low vis-cosity grade of sodium alginate; and KELGIN XL is a refined, extra low viscosity grade of sodium alginate~

TABLE III
Dewatering Index At Indicated Concentration Dewatering A&ent (Wt %) Sodium Alginate ~F~LCOGEI LY~ ~2 70 56 52 --Sodium-~Alg~nat2 (KELGIN RL) 85 78 72 68 65 ~o~ium Al~inat~ (KELGIN XL) 92 85 75 __ __ EXAMPLE IV

Flattened collagen tubing prepared as described in Example I is collected after the final washing step and stored frozen for use in carrying out the evaluation tests of this example.
Samples of thawed, flattened collagen tubing weighing about 10 grams are blotted thoroughly with a cloth towel to remove surface water and then weighed to the nearest 0.01 grams. Samples of weighed collagen tubing are then \1~ 15, ~ , . , . , . ; :, ~ 8~53~ 9744 trea~ed in aqueous dip baths containing sodium alginate, with agitation, for varying lengths of time. After treat-ment, the tubing samples are blotted and weighed and the dewatering index is calculated.
The results of the dewatering treatment are summarized in Table IV. The sodium alginate used in this example is KELCOGEL LV and KELGIN RL.

TABLE IV

Dip Bath Treatment Concentration Time Dewatering Sodium Alg m ate`(% ~t.)- Minutes Index K~LCOGEL LY l Q 1 30 79 ~' lqO 3,0 79 " 1.0 5.0 74 " 1.0 10.0 68 " 1,0 30.0 67

4,0 0.05 (3 secs) 75 " 4 0 0.3 71 " 4 0 0.5 70 " 4.0 0.7 6g " * 4.0 1.0 59 " 4,0 3.0 63 " 4 0 5.0 60 " 4 0 10.0 61 " 4.0 30.0 76 The results in Table IV show that treatment times as short as 3 seconds will afford appreciable dewater-ing and that dewatering is generally more effective when longer treatment times are used.

16.

Claims (10)

WHAT IS CLAIMED IS:

1. In a method of producing shaped collagen structures the improvement which comprises treating a shaped collagen structure prior to the final drying thereof with a dewatering solution comprising at least about 0.01% by weight of sodium alginate.

2. The method of claim 1 wherein said shaped collagen structure is a tubular food casing.

3. The method of claim 1 wherein said dewatering solution is an aqueous solution.

4. The method of claim 2 wherein treatment of said collagen structure is carried out by immersing said structure in an aqueous dewatering solution.

5. The method of claim 4 wherein said collagen structure is immersed in said dewatering solution for at least 3 seconds.

6. The method of claim 4 wherein said aqueous dewatering bath additionally comprises glycerine.

7. The method of claim 1 wherein said dewatering bath contains up to about 10% by weight of sodium alginate.

8. The method of claim 4 wherein said aqueous dewatering bath comprises at least about 0.5% by weight up to about 10% by weight of sodium alginate.

9. The method of claim 6 wherein said collagen structure is treated with said dewatering solution for between about 3 and 7 minutes.

10. The method of claim 1 wherein said collagen structure is dried after treating with said dewatering solution.

17.