Collagen compositions

Improved collagen compositions having incorporated therein relatively small amounts of propylene glycol alginate.

The present invention relates to improved collagen food casings and to 
their preparation. 
For a number of years thin-wall sausage casings have been prepared from 
processed animal collagen and, more recently, edible casings of collagen 
have been prepared and sold in commercial quantities. Commercially 
available edible collagen casings have proven to be a suitable replacement 
for natural casings in the preparation of food products, such as fresh 
pork sausages, wherein a meat emulsion of the pork sausage type is 
stuffed, linked and packaged without cooking, the encased sausage product 
then being suitable for cooking by the consumer without the need to remove 
the casing. Edible collagen casings have also been used for preparing 
sausage products, such as frankfurters, wherein the stuffed and linked 
food casings are cooked prior to packaging, but the highly automated 
processing techniques and wide variety of processing procedures that are 
employed have presented many difficulties and have limited the acceptance 
thereof. 
The delicate, fragile nature of formed collagen structures, such as food 
casings, and problems encountered during the processing thereof are well 
known and methods of overcoming such problems have been the subject of a 
number of patents. A number of recent patents have also been directed to 
the preparation of edible collagen food casings that exhibit improved 
physical properties or that meet other special requirements for food 
casings, such as their performance during stuffing and cooking operations. 
It is well known, for example, as disclosed in U.S. Pat. Nos. 3,123,482 and 
3,413,129 to Lieberman, U.S. Pat. No. 3,446,633 to Talty, and U.S. Pat. 
No. 3,525,628 to Cohly, that collagen tubing prepared by extruding a 
fluid, low collagen solids mass involves processing by passing the tubing 
through a bath containing chemical hardening or tanning agents. 
Alternative methods, such as disclosed, for example, in U.S. Pat. Nos. 
3,551,535 and 3,782,977 to Henderson et al., provide for the preparation 
of collagen tubing from collagen compositions containing collagen solids 
greater than 6% without the need for chemical hardening agents. 
Whereas the casings prepared by treatment with tanning agents are generally 
quite strong and can be handled during processing, reeling, shirring, 
packaging, etc., in view of the difficulties encountered during the 
various processing operations, the development of a process for the 
production of collagen casing having satisfactory strength and handling 
characteristics without the need for subjecting the tubing to tanning 
agents would be desirable. Casings prepared by extruding high collagen 
solids compositions have been found to be strong enough to exhibit 
suitable handling and processing characteristics without the need for 
treatment with chemical hardening agents. It has been found, however, that 
casings which are shirred and packaged satisfactorily, and handle properly 
during stuffing, may have insufficient strength during cooking. The 
development of a process that would also eliminate or improve such 
characteristics would, therefore, be a desirable improvement. 
It has been suggested in the past, as, for example, disclosed in U.S. Pat. 
Nos. 2,114,220 to Freudenberg et al, 3,446,633 to Talty and 3,551,535 to 
Henderson et al., that various materials may be incorporated in collagen 
compositions during their preparation to improve or modify the properties 
of the collagen structures prepared therefrom; and as disclosed, for 
example, in U.S. Pat. No. 3,627,542 to Cohly et al., that materials may be 
used to treat tubular collagen casings during the processing thereof to 
improve the casing cooking properties. Further, in U.S. Pat. No. 3,956,512 
to T. E. Higgins, a process is described in which formable collagen 
compositions are prepared having certain types of fatty acid esters 
incorporated therein, the tubular food casing prepared therefrom 
exhibiting improved anti-block characteristics and improved casing cooking 
properties. 
The need still exists for the development of even further improvements in 
the cooking and handling properties of collagen food casings, particularly 
when such improvements can be realized in simple manner without increasing 
the number or difficulty of processing steps for the preparation of the 
tubular food casing. 
The present invention provides improved collagen compositions having 
incorporated therein relatively small amounts of a propylene glycol 
alginate. The incorporation of a relatively small amount of a propylene 
glycol alginate in collagen compositions surprisingly and unexpectedly 
results in shaped collagen structures such as, for example, tubular 
collagen food casings, that exhibit improved strength characteristics 
without the need for treatment with or addition of other chemical 
hardening or tanning agents. 
The propylene glycol alginate is incorporated in the collagen compositions 
in accordance with this invention in an amount between about 0.2% and 5% 
by weight of the dry solids content of the collagen composition. The 
amount of the propylene glycol alginate employed is fairly critical to 
obtain the desired improvements. Use of the propylene glycol alginate in 
amounts substantially greater than about 5% have detrimental effects on 
the properties of the composition in use. Preferably, the propylene glycol 
alginate is employed in an amount corresponding to about 3% by weight of 
the dry solids content of the collagen composition. "Dry solids content" 
as used herein with respect to the collagen compositions and casings 
refers to the weight of all ingredients in such compositions and casings 
excluding water and glycerol. 
The collagen can be prepared by any of 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. 
Propylene glycol alginates, which are propylene glycol esters of alginic 
acid, are known materials available commercially in various viscosity 
grades. Thus, for example, various viscosity grades of propylene glycol 
alginates are available from the Kelco Company under the trade designation 
Kelcoloid, as well as from Alginate Industries, Ltd. 
To obtain the collagen compositions of the present invention, the propylene 
glycol alginate is mixed with the swollen collagen, that is, after the 
collagen tissue has been swollen by treatment with a collagen swelling 
agent such as hydrochloric acid, but prior to forming desired shaped 
structures therefrom such as, for example, tubular food casings. In this 
manner, the propylene glycol alginate is incorporated and uniformly 
dispersed in the wall of the shaped collagen structure, eliminating the 
need for certain processing steps and for treatment with certain of the 
agents generally employed during the processing sequence for tubular 
collagen structures such as food casings. 
In a preferred embodiment of the invention, collagen-containing tissue as, 
for example, limed animal hide splits, cleaned and prepared by methods 
well known in the art, are diced or coarsely chopped into pieces about 1/2 
to 2 inches in size to facilitate transfer and agitation. After an 
additional treatment with lime and subsequent water wash, the hide pieces 
are subjected to treatment with a collagen swelling agent. Any of the 
known collagen swelling agents may be employed, but it is preferred to use 
dilute lactic, acetic or hydrochloric acid solutions. Collagen pieces are 
treated with swelling agent for an extended period of time, such as, for 
example, 4 to 9 hours or even longer, and, generally, until the character 
of the collagen material has completely changed from opaque to 
translucent. The swollen collagenous material is then washed with water to 
reduce the amount of residual acid and, generally, until the pH of the 
comminuted swollen collagen ranges between about 2.5-3.5. The swollen 
collagen is then drained, leaving pieces generally referred to as 
"acid-swollen chips." 
As disclosed in U.S. Pat. No. 3,782,977 to Henderson et al., 
non-collagenous fibers that are to be incorporated into the collagen 
composition are first formed into a viscous aqueous fibrous dispersion 
that may contain between about 2 and 10% by weight of the non-collagenous 
fibers and between about 0.1 and 10% by weight of a viscosity control 
agent that is preferably water soluble or water dispersible. Suitable 
viscosity control agents include, for example, methyl cellulose, gelatin, 
starch, and particularly, a dispersion of swollen collagen particles. 
Non-collagenous fibers that may be employed are any of the non-shrinking 
and essentially inert fibrous additives known to be suitable in collagen 
compositions such as, for example, wood, cotton, rayon, other cellulosic 
fibers, non-cellulosic fibers such as polyester, polyamide and the like. 
Acid-swollen chips to be used in the preparation of the formable collagen 
composition are, preferably, furthercomminuted prior to mixing with the 
aqueous fibrous dispersion. The acid-swollen chips may be partially 
subdivided by means known in the art, such as by coarse grinding or 
crushing, to prepare a mass containing a predominance of chunks having 
major dimensions of about 1/8 to 1/2 inch. 
The propylene glycol alginate, water as water or ice, and a portion of the 
acid-swollen collagen chips are added to and thoroughly mixed with the 
viscous fibrous dispersion in a suitable dough mixer or other similar 
mixing equipment, and then the remainder of ground, acid-swollen chips are 
admixed therewith, whereby the fibrous additive and propylene glycol 
alginate components are uniformly distributed throughout the collagen mass 
in a relatively short time, as, for example, between about 2 and 10 
minutes. Towards the end of the mixing step, the collagen mass becomes 
much more viscous, which helps in preventing separation of the various 
components during forming and subsequent processing thereof. 
It is important that during grinding and mixing of the acid swollen chips, 
the temperature of the collagen mass be kept low and the temperature of 
the mass is, in general, maintained below about 25.degree. C. 
The collagen composition that is prepared preferably comprises at least 
about 6% by weight of collagen solids, and has uniformly incorporated 
therein between about 5 and 30% by weight of non-collagenous fibers based 
on the weight of total dry solids. 
In alternative embodiments of the invention, the propylene glycol alginate 
can be added directly to the fibrous dispersion mixture before mixing the 
same with the ground acid swollen chips or it can be added to a swollen 
low collagen solids slurry prepared in accordance with any of the methods 
known in the art before or after adding other ingredients thereto. 
The uniform high collagen solids composition so prepared is suitable, with 
only limited further processing, for forming into commercially acceptable 
formed or extruded collagen structures. A screw extruder or similar device 
can be used to transfer the collagen composition to homogenization 
equipment used in final preparation of the composition for extrusion. 
Exemplary of a preferred method of preparing a tubular collagen structure 
such as, for example, a tubular food casing, a collagen composition of the 
invention 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 passing through 
water tanks, and then plasticized by being conveyed through a dilute 
glycerine solution. The tubing is then reinflated with low pressure air, 
conveyed through a dryer while maintaining the tubular configuration, and 
then, if desired, shirred into a shirred casing stick by passing through a 
shirring apparatus. 
Collagen tubing prepared from collagen compositions of the invention in the 
manner herein described perform satisfactorily through each of the various 
processing steps with, in general, no problems being encountered. 
Moreover, it has been found that tubular collagen casing prepared in 
accordance with the practice of the invention, performs very 
satisfactorily during stuffing, linking and cooking operations. 
Tubular collagen food casings of the present invention have the propylene 
glycol alginate uniformly incorporated therein in an amount of at least 
about 0.1 up to about 3.0% by weight, and preferably between about 0.6 to 
about 1.9% by weight, of all components of said casing. Especially 
preferred are tubular collagen food casings having uniformly incorporated 
therein from about 3.0 to about 19.0% by weight of non-collagenous fibers 
based on the weight of all components of said casings.

The following examples are set forth as illustrating 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. 
EXAMPLE I 
1630 Pounds of limed beef hide splits were chopped into approximately 1/2 
to 2 inch 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 treatment 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 maintained at a pH of 1 using a flow rate of dilute acid of 10 
gallons per minute. At the end of the acid swell treatment, the swollen 
chips were washed with water at 10 gallons per minute for about 5 hours 
until a wash water pH of 2.6 was reached. The chips were drained and 
chilled to about 1.degree. C. 
A cellulose fiber dispersion was prepared using the following ingredients: 
______________________________________ 
Collagen Composition (11.1% solids = 9.4% 
collagen solids and 1.7% cellulose fibers) 
254 pounds 
Wood Cellulose Fibers 155 pounds 
Water 2186 pounds 
______________________________________ 
The wood cellulose fibers used had an average fiber length of about 0.04 
inch. 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 for an additional 30 minutes, and then mixed for about 2 
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 collagen solids 1%, wood cellulose fibers 5.6% and water 
93.4% 
A series of collagen compositions having a total solids of 11.1% were 
prepared. These compositions had total weights and solids ingredients as 
follows: 
______________________________________ 
Percent of Composition Solids 
Composition Propylene 
Collagen Weight Cellulose 
Glycol 
Composition 
(lbs.) Collagen Fiber Alginate 
______________________________________ 
A 210 85 15 0 
B 50 82 15 3 
C 50 80 15 5 
______________________________________ 
The collagen compositions were prepared by mixing weighed portions of 15.2% 
solids ground, acid-swollen chips, cellulose fiber dispersion, water and 
propylene glycol alginate. 
Acid-swollen chips prepared as described above were ground in a meat 
grinder into pieces substantially between about 1/8 and 1/2 inch in size 
prior to blending with the viscous cellulose fiber dispersion. The 
temperature during grinding of the chips was controlled so as not to 
exceed about 20.degree. C. The propylene glycol alginate used in this 
example was propylene glycol alginate LF/5, a product of Alginate 
Industries, Ltd. The propylene glycol alginate was dissolved in water as a 
4.6% solution prior to mixing with the other ingredients of the collagen 
composition. 
The propylene glycol alginate solution was mixed with the cellulose fiber 
dispersion. Water and ground acid-swollen chips were then added and the 
composition was mixed for about five minutes at which time the composition 
was homogeneous and began to adhere to the mixing equipment. The 
temperature of the various materials during the mixing step was controlled 
so as not to exceed 20.degree. C. 
After preparing the collagen compositions, they were 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.degree. C. 
After homogenization, the blend was pumped through two parallel filters 
with 0.003 inch slots to break up any remaining collagen lumps and remove 
any nondispersed matter. 
The filtered collagen blends were pumped and metered through an extrusion 
nozzle to form a continuous tube of collagen. The extruded tubes were 
inflated with low-pressure inflation air while being conveyed on 
horizontal rolls. 
The inflated collagen tubing was partially dried and hardened by passing 
through a predryer at 50.degree. C., 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 a solution of 4.5% 
glycerol in water. 
The tubing samples were then reinflated with low pressure air, dried in air 
at 100.degree. C., moisturized in an equalizer at 70% RH and then shirred 
by passing through a shirring apparatus. A small amount of edible oil was 
added to the casing as a lubricant during shirring. 
After shirring, the casing was baked at 72.degree. C. for 20 hours, cooled, 
humidified to 15% moisture by passing humid air through the casing, and 
packaged. 
Propylene glycol alginate containing casings showed improved strength and 
processing compared to the control. The finished casings had the following 
composition: 
______________________________________ 
Composition (% of Total Casing Weight) 
Collagen 
Propylene 
Compo- Glycol Col- Glyc- Cel- Edible 
sition Alginate lagen erol Water lulose 
Oil 
______________________________________ 
A 0 53.8 18.4 15.0 9.5 3.3 
B 1.9 51.9 18.4 15.0 9.5 3.3 
C 3.2 50.6 18.4 15.0 9.5 3.3 
______________________________________ 
Test results on the finished casings are shown in Table 1. Cooked strengths 
were increased and pressures required to unshirr the casing were reduced 
when propylene glycol alginate was present in the composition. 
TABLE 1 
______________________________________ 
Cooked burst pressures and unshirring pressures for propylene 
glycol alginate containing collagen sausage casings. - 
Propylene Glycol 
Cooked burst 
Unshirring 
Collagen 
alginate (% of 
pressure (mm) pressure (mm 
Composition 
Total casing weight) 
of mercury) of mercury) 
______________________________________ 
A 0 64 22 
B 1.9 77 16 
C 3.2 73 12 
______________________________________ 
Cooked burst pressures were increased for the propylene glycol alginate 
containing casings (Compositions Band C, Table 1) compared to the control 
casing (Composition A, Table 1). Cooked burst pressures were measured by 
soaking the casing in water, immersing the casing in boiling water for two 
minutes, cooling the casing, and then measuring the pressure in 
millimeters of mercury required to burst the casing. 
Table 1 compares unshirring pressures for the casings of Example I. 
Pressures required to unshirr casings B and C containing propylene glycol 
alginate were reduced compared to casing A which contained no propylene 
glycol alginate. A low pressure required to unshirr casing can prevent 
breakage during stuffing of the sausage casing with meat emulsion. The 
unshirring pressure is measured by inflating a shirred stick of casing 
with air and measuring the pressure required to unfold the casing as it 
fills with air. 
This example shows that propylene glycol alginate, when incorporated into 
collagen compositions at 3% and at 5% of dry solids content thereof, 
increases cooked strength and reduces pressures required to unshirr the 
casing. 
EXAMPLE II 
This example describes the use of propylene glycol alginate to strengthen 
collagen strands. Strength measurements on the resulting strands show that 
propylene glycol alginate strengthens shaped collagen articles when 
incorporated into collagen compositions in amounts up to about 5% of dry 
solids content. Collagen strands are prepared more readily than is 
collagen casing. The effect of different levels of propylene glycol 
alginate on the strength of a formed collagen article can be readily 
determined by making collagen strands. 
1493 Pounds of limed beef hide splits were chopped into approximately 178 
to 2 inch pieces and subjected to an additional lime treatment by charging 
into a tank together with 105 pounds of lime and sufficient water to give 
a water to hide ratio of 4.4 to 1. The lime treatment was continued for 91 
hours with intermittent agitation after which the limed hide chips were 
leached with 30 gallons per minute of water for eight hours and with 15 
gallons per minute of water for 14 hours. The hide chips were than swollen 
for 9 hours in a hydrochloric acid solution maintained at a pH of 1 using 
a flow rate of dilute acid of 10 gallons per minute. At the end of the 
acid swell treatment, the swollen chips were washed with water at 30 
gallons per minute for about 1.5 hours until a wash water pH of 2.6 was 
reached. The chips were allowed to equilibrate for 17 hours in the dilute 
acid solution, then drained and chilled to about 1.degree. C. 
A collagen fiber dispersion was prepared as described in Example I. 
Collagen compositions having a total solids of 11.1% were prepared as 
described in Example I. Propylene glycol alginate was added as a 12.9 
percent solution in water. The collagen compositions had solid ingredients 
as follows: 
__________________________________________________________________________ 
Percent of Composition Solids 
Propylene Glycol Alginate 
Propylene Glycol 
Cellulose 
Sample 
Manufacturer 
Type Alginate Collagen 
Fiber 
__________________________________________________________________________ 
A control for Samples B through E 
0 85 15 
B Alginate Industries 
KL3 1.0 84 15 
C Alginate Industries 
KL3 5.0 80 15 
D Alginate Industries 
KL3 10.0 75 15 
E Alginate Industries 
KL3 20.0 65 15 
F Control for Samples G through J 
0 85 15 
G Alginate Industries 
LF5 1.0 84 15 
H Alginate Industries 
LF5 3.0 82 15 
I Alginate Industries 
LF5 5.0 80 15 
J Alginate Industries 
LF5 10.0 75 15 
K Control for Samples L through O 
0 85 15 
L Kelco Kelcoloid S 
1.0 84 15 
M Kelco Kelcoloid S 
5.0 80 15 
N Kelco Kelcoloid S 
10.0 75 15 
O Kelco Kelcoloid S 
20.0 65 15 
__________________________________________________________________________ 
Propylene glycol alginate type KL3 is a high viscosity grade of propylene 
glycol alginate. Propylene glycol alginate LF5 is a low viscosity 
propylene glycol alginate. Both of these propylene glycol alginates were 
obtained from Alginate Industries Limited, London, England. Kelcoloid S is 
a low viscosity propylene glycol alginate obtained from Kelco Company, San 
Diego, California. 
The collagen compositions were homogenized by pumping them through 1 
millimeter diameter holes and then through three sets of 0.08 millimeter 
wide slots. The resulting homogenized collagen compositions were extruded 
through a 0.3 millimeter diameter orifice and then through a 2.2 
millimeter diameter orifice into a neutralization bath containing 0.06 N 
ammonia. 
The resulting collagen strands remained in the ammonia solution for 20 
minutes at which time they were fully neutralized. The strands were then 
washed with water for twenty minutes and then plasticized in a 4.4% 
glycerol solution for 13 minutes. The strands were dried under a 5 gram 
tension at ambient temperature and baked for 20 hours at 72.degree. C. 
To minimize unavoidable variations among experimental samples, strands 
containing the same propylene glycol alginate and the respective control 
were prepared together. Strands containing Alginate Industries KL3 
(Samples A through E) were prepared together. Likewise, strands containing 
Alginate Industries LF5 (Samples F through J) were prepared together as 
were strands containing Kelcoloid S (Samples K through O). 
Table 2 shows the strength properties of the resulting strands. The 
strength measurements were made by draping a single cut collagen strand 
over a 3/8 inch diameter rod fastened to the pan of a direct reading 
balance. The strand ends were pulled downward. The balance reading at the 
time the strand broke was recorded. The values recorded in Table 2 are the 
average of five to 10 determinations. 
TABLE 2 
__________________________________________________________________________ 
Strength Measurements of Collagen Strands Containing Propylene Glycol 
Alginate 
Strengths (grams) 
Propylene Glycol Alginates Before Baking 
% of Composi- 
Gel After 
Wet After 
After Baking 
Sample 
Manufacturer 
Type tion Solids 
Final Bath 
Drying 
Wet Cooked 
__________________________________________________________________________ 
A Control for Samples B through E 
0 231 359 445 241 
B Alginate Industries 
KL3 1.0 262 454 500 268 
C Alginate Industries 
KL3 5.0 275 430 462 334 
D Alginate Industries 
KL3 10.0 140 267 334 280 
E Alginate Industries 
KL3 20.0 Strands too weak to be processed 
F Control for Samples G through J 
0 202 408 491 315 
G Alginate Industries 
LF5 1.0 244 452 528 337 
H Alginate Industries 
LF5 3.0 257 438 622 374 
I Alginate Industries 
LF5 5.0 215 419 578 344 
J Alginate Industries 
LF5 10.0 185 356 506 312 
K Control for Samples L through O 
0 224 515 542 284 
L Kelco Kelcoloid S 
1.0 250 573 615 349 
M Kelco Kelcoloid S 
5.0 222 547 619 357 
N Kelco Kelcoloid S 
10.0 173 442 491 345 
O Kelco Kelcoloid S 
20.0 92 302 368 242 
__________________________________________________________________________ 
Gel strength measurements were made on the wet, plasticized strands 
immediately after treatment in the glycerol bath. Wet strengths were 
measured after soaking the strands in water for 10 minutes prior to the 
measurement. Wet strengths were measured on strands prior to baking and on 
strands after baking. Cooked strengths were measured on baked strands 
after soaking the strands in water for 10 minutes, immersing them in 
boiling water for 2 minutes, and cooking them in cold tap water. 
The strength measurements show that 1, 3 and 5% propylene glycol alginate 
increase the strength of collagen strands. Thus, Samples B, C, G, H, I and 
L containing 1, 3 and 5% propylene glycol alginate had higher gel 
strengths, higher wet strengths and higher cooked strengths than did 
Samples A, F and K, the respective control samples containing no propylene 
glycol alginate. Sample M containing 5% propylene glycol alginate had a 
gel strength slightly lower than its control, Sample K, but other 
strengths were higher than the control. 
The strength measurements show that 20% propylene glycol alginate weakened 
the collagen strands. Thus, Sample O, containing 20% propylene glycol 
alginate, had a lower gel strength, a lower wet strength and a lower 
cooked strength than did Sample K, the control sample containing no 
propylene glycol alginate. Sample E, containing 20% propylene glycol 
alginate, gave strands too weak to be processed. 
The strength measurements also show that on balance 10% propylene glycol 
alginate also weakened the collagen strands. Thus, Samples D and N, 
containing 10% propylene glycol alginate, had lower gel strengths and 
lower wet strengths than did Samples A and O, the respective controls. 
Samples D and N had higher cooked strength than did their control, Sample 
J, containing 10% propylene glycol alginate, had a lower gel strength and 
a lower wet strength before baking than did Sample F, the control. Sample 
J also had a lower cooked strength than did Sample F, the control. Sample 
J had a higher wet strength after baking than did Sample F. 
This example shows that propylene glycol alginate, when incorporated into 
collagen compositions in amounts of 5% and below of dry solids, 
strengthens shaped collagen articles. 
In producing the collagen composition of the present invention, any other 
ingredient well known to those skilled in the art which can be utilized to 
impart a particular characteristic or property to collagen structures 
obtained therefrom may also be present, if desired. Moreover, the collagen 
compositions of the invention may be shaped or formed into any of a wide 
variety of desired structures. 
Those modifications and equivalents which fall within the spirit of the 
invention are to be considered a part thereof.