Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
-` 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.
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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.
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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
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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
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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
531
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-
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." ' ': ' " ' ''`........ ~
9744
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.
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53
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 ~
,.",. . . .
, ~
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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.
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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.
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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.
9744
: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
KELGIN RL 4 0 1 0 73
" 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.
