Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~3, FOOD CASING BASED ON CELLULOSE CONTAINING
,, CROSSLINKED PROTEIN COMPOUNDS
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,'~ Backaround of the Invention
'~ . The present invention relates to a tubular, 5 food casing, in particular a synthetic sausage casing
~, for types of uncooked sausage and scalded., sausage,
~ constructed from a base tube based on cellulose
:1 hydrate which optionally contains fiber
reinforcement. The invention furthermore relates to
the use of this casing and to a process for the pro-
' duction thereof in which alkaline viscose is
j converted into regenerated cellulose by acid
'~ coagulation.
,l Tubular food casings based on cellulose
~ 15 hydrate and having an inside which has not been
.~ pretreated are only suitable to a limited extent for
, use as sausage casings since the sausage meat in
fresh sausage adheres to the casing so strongly that
the latter can hardly be removed from the filling
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when required: in the case of uncooked sausage, such
as, for example, long-keeping sausage, the adhesion
is, in contrast, so low that the casing already
separates from the sausage meat during the drying
process in storage. As a consequence of the
detachment of the casing from the sausage meat on
drying of long-keeping sausage, the casing does not
shrink along with the filling, and the package casing
, therefore becomes wrinkled and unattractive.
In order to solve this problem, European
Patent No. 88,308 discloses providing the inside of
the tube with a coating of a water-insoluble resin,
such as, for example, protein-formaldehyde resin, and
an oil. The uncrosslinked protein-formaldehyde
15 solution is applied to the inside of the coagulated
1~ tube made from cellulose hydrate gel and is linked to
j the cellulose surface on subsequent drying.
However, the production of these coatings does
not succeed satisfactorily, in particular as far as
20 the evenness of the weight applied per unit area and
.thus the thickness of the coating is concerned.
The amount of coating applied to the cellulose
3 surface, 40 to 120 mg of resin per m2 according to
this publication, is subject to great variations,
25 even when the concentration of the solution is kept
constant. In addition, it is impossible to set
exactly the optimum application rate, which is
responsible for an improvement in the adhesion
properties of the tubular casing, via the concen-
30 tration of the solution. This is particularly
disadvantageous since a certain, essentially narrower
range for the application rate compared to the
overall range described above should be maintained
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for each type of sausage. If the optimum application
rate is exceeded, peeling difficulties occur, and if
less than the optimum rate is used, the tubular
casing detaches from the filling on storage of the
sausage.
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Summary of the Invention
It is therefore an object of the present
invention to improve tubular food casings of the type
mentioned initially.
loIn particular, it is an object to provide a
tubular food casing having a coating of even, optimum
-~, thickness formed on its inner surface.
~ It is also an object of the invention to
;~ provide an improved sausage product embodying the
improved sausage casing according to the invention.
~ Still another object of the invention resides
in the provision of a process for producing the
~a improved sausage casings.
In accomplishing the foregoing objects, there
has been provided in accordance with one aspect of
the present invention a tubular food casing,
comprising a base tube comprised of cellulose hydrate
having dispersed therein a protein compound which is
soluble or dispersible in alkali, is hydrolysis-
resistant and is crosslinked with an alkali-resistant
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reactive compound. Preferably, the food casing
~,comprises a sausage casing.
In accordance with another aspect of the
invention, there has been provided an uncooked
sausage or a scalded sausage product comprising a
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,~q sausage meat contained in a tubular casing as defined
~' above.
. In accordance with still another aspect of the
present invention, there has been provided a process
5 for the production of a food casing as defined above.
3 The process comprises the steps of extruding an
~, alkaline viscose solution as a tube; coagulating and
`i regenerating the viscose to form cellulose hydrate
-~f' gel; and drying the product obtained, wherein the
10 process further comprises the steps of adding a
protein compound and a crosslinking agent to the
~;f viscose before extrusion, and crosslinking the
protein compound during the drying step.
According to the invention, the amount of
15 active compounds, in particular based on water-
insoluble resins, applied to the inside can be
f adjusted to an optimum value in order to improve the
adhesion properties between the inside of the
;~ covering and the sausage meat, and can be kept
20 substantially constant.
Other objects, features and advantages of the
present invention will become apparent from the
following detailed description of preferred
embodiments. It should be understood, however, that
~; ~ 25 the detailed description and the specific examples,while indicating preferred embodiments of the
invention, are given by way of illustration only,
since various changes and modifications within the
spirit and scope of the invention will become
30 apparent to those skilled in the art.
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Detailed Description of Preferred Embodiments
The tubular food casing comprises a base tube
based on cellulose which is optionally provided with
fiber reinforcement, for example, made from a fleece
of hemp fibers or a paper insert. The fiber
reinforcement is impregnated on both sides with
~ viscose so that the resultant tube has a cellulose
- coating on the outer and inner surfaces after
regeneration of the cellulose.
~, 10 The cellulose contains an additive comprising
one or more protein compounds, in particular natural
protein compounds of animal or vegetable origin,
;5 which are soluble or dispersible in an alkaline
'~'5, aqueous medium at concentrations of about 1 to 20% by
15 weight, which have a viscosity that allows metering,
~' and which are sufficiently hydrolysis-resistant in
the alkaline viscose solution. These compounds
include gelatin, soya protein, wheat protein and
."5 groundnut protein, but casein is particularly
~ 20 preferred. These compounds are readily accessible
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and inexpensiv~.
As suitable agents for crosslinking of the
J protein molecules with one another and with the
cellulose molecules surrounding them, alkali-
25 resistant reactive compounds are used which add to
the amino groups of the protein compound, initially
with formation of methylol groups, and react with the
OH groups of the cellulose molecule during the actual
thermal crosslinking with elimination of water.
~- 30 These crosslinking agents include, in particular,
aldehydes, such as formaldehyde, and dialdehydes,
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such as glyoxal, malonaldehyde and glutaraldehyde.
of these, glyoxal is preferred. The amount of
crosslinking agent is preferably matched to the
- particular specific protein compound. The amount of
crosslinking agent should be sufficient to react with
the amino groups of the protein compounds. Thus, at
-~ least 3% of crosslinking agent should expediently be
used for casein in order to achieve sufficient
linking. In general, the suitable amount is from
about 2 to 10%, in particular from about 3 to 6%,
relative to the weight of the protein compound. The
- suitable amount of protein dispersed in the cellulose
-- hydrate of the basetubeisupto about 50, preferably
from about 0,5 to 25, in particular from about 0.8 to
15 X by weight, relative to the cellulose.
~ ~~~~~ The food casing can be used without a further
;~y - inner coating which influences the adhesion between
~ the sausage meat and cellulose casing and is suitable
;~ as a synthetic sausage casing for varieties of
sausage which are easy to peel. These include some
varieties of scalded sausage in which the sausage
--~, meat does not contain any highfat skin components, or
long-keeping types of saùsage, such as pepperoni,
which are only matured for a short time so that the
sausage meat only shrinks a little.
For long-keeping varieties of sausages of the
true salami type which are provided with a true mold
growth on their outer surface and have to mature for
many weeks and even months, an additional inner
coating is necessary of crosslinked cationic resins
which preferably comprise crosslinked protein
~ compounds that exhibit greater adhesion to the
Tj sausage meat compared to epichlorohydrin/polyamine
-~ polyamide resins. The crosslinking of the protein
3~ compound in the inner coating takes place using the
same agents as in the base layer, glyoxal again being
the ideal crosslinking agent. The proportion of
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20731-994
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crosslinking agent relative to the protein compound is from
about 2 to 20%, preferably from about 3 to 8% by weight. This
inner coating may also contain an additional oil such as an oil
selected from a paraffin oil and/or a silicone oil preferably
wherein the oil comprises a triglyceride mixture with vegetable
fatty acids, as described in European Patent No. 88,308.
However, even substantially lower amounts of cationic resin
coating are sufficient to achieve a good effect for the adhesion
between the cellulose and the dried and shrunk sausage meat.
The tubular covering is produced by the known
viscose process. The protein compound is added together with
the crosslinking agent in alkaline solution or dispersion to the
alkaline viscose solution, just before extrusion of the viscose.
The added solution or dispersion usually contains from about l
to 20%, preferably from about 2 to 15~, and in particular from
about 3 to 10% by weight of protein compound, relative to the
cellulose, with the crosslinking agent being bound to the amino
groups of the protein molecules with formation of methylol
groups.
The viscose is coagulated and regenerated under
customary conditions. The cellulose hydrate gel tube is passed
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through wash baths and plasticiæer baths and dried in a blown-
up state at from about 90 to 150C. During the drying process,
the protein molecules are thermally crosslinked to one another
and to the cellulose molecules.
Surprisingly, the protein compound is only dissolved
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out to an insignificant extent on passing from the extrusion
die to the dryer. At least 60 to 90% by weight of the metered-
in amount of protein compound are still present in the dried
tube. This e~fect can be attributed to the low tendency of the
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`~protein molecules to diffuse out of the cellulose
material after the precipitation reaction. The even
,distribution of the protein molecules over the cross-
1~section of the cellulose layer is furthermore
-~5 notable, so that an adequately high concentration of
protein molecules is found even in the regions in the
-~vicinity of the surface.
If an additional coating is provided on the
inner layer of the tubular casing in order to improve
~10 the adhesion properties, this coating expediently
`ltakes place before drying of the cellulose hydrate
gel, as described in European Patent No. 88,308.
By modifying the cellulose layer of the
tubular covering in the manner of the invention, a
,15 marked improvement in the adhesion properties is
achieved in a simple and inexpensive way. Substances
~;1are employed which are acceptable from the point of
view of food regulations. The invention allows exact
~grading of the effect of the inner coating and thus
:.;20 also of the adhesion properties. The desired quality
;~can be kept constant, which is particularly important
q~in perishable types of sausage. The adhesion of the
;~sausage meat to the cellulose inner wall is uniform,
both around the circumference and along the length of
the tubular cover.
The invention is described in greater detail
with reference to the non-limiting examples which
~; follow.
Example 1
6.4 l of an alkaline solution of the following
composition are metered into 172 l of an alkaline
viscose solution (cellulose xanthogenate) having a
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. cellulose content of about 7% by weight just before
; the extrusion die:
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;-~ 0.6 kg of milk protein (~Rovita FN 4,
manufacturer Rovita, Aschau)
~; 5 0.3 1 of sodium hydroxide solution, (4%
strength by weight)
0.045 1 of glyoxal, (40% strength by
~ weight, corresponding to 3%
`~ relative to milk protein) and
~;~ 10 10.455 1 of water.
~, The content of milk protein (casein) in the
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resultant mixture is about 3~ by weight, relative to
$~ the cellulose.
A paper fiber web rolled to form a tube is
impregnated on the inside and outside in the weight
ratio 7:3 with this viscose solution by extrusion
dles as described in German Patent No. 1,965,130,
and passed in a known fashion through an acidic
precipitation bath and regeneration baths; the tube
is washed, treated with plasticizer (glycerol) and
dried in the blown-up state. The tube has a diameter
of 40 mm.
The protein content in the finished tube is
2.8~ by weight, relative to the cellulose, or 1.9% by
weight, relative to the total weight. The tube
contains 93% of the metered-in amount of protein.
Sausages of the salami type are produced from
the tube and these are assessed for peelability after
a maturing time of 2 weeks. on an assessment scale
of 1 to 5 and an aimed-at effect of 2 to 4, a value
of 2.5 is achieved.
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~ Example 2
`l In an analogous fashion to that described in
Example 1, a fiber skin of 40 mm diameter is again
produced, the addition to the viscose solution being
changed. 3.2 1 of alkaline solution of the following
composition are metered into 172 1 of viscose
solution:
:~! O. 6 kg of soya protein (~Purina PP 500E)
manufacturer: Ralston Purina Co.)
lO 0.3 l of alkali lye (4~ strength by
~ weight)
`; 0.045 1 of glyoxal (40% strength by weight)
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10.455 l of water.
The content of soya protein in the resultant
~ mixture is 1.5% by weight, relative to the cellulose.
`~ The proportion of soya protein in the finished tube
is about 1.4% by weight, relative to the cellulose,
corresponding to 1~ by weight relative to the tube
weight. Of the metered-in amount of soya protein,
92% are still present in the final product.
The peelability of salami, assessed
analogously to Example 1, is given the value 2.
Example 3
' 25 A fiber skin which has been viscose-treated on
both sides and has a diameter of 60 mm is produced
corresponding to the examples above. 13.2 1 of an
alkaline solution of the following composition is
added to 190 l of alkaline viscose solution:
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0.6 kg of soya proteln ( Purina 500 E)
0.3 l of alkali lye (4% strength by
weight)
0.045 l of glyoxal (40% strength by
~ 5 weight) and
', 10.455 l of water.
The content of soya protein in the resultant
mixture is 5% by weight, relative to the cellulose.
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The content of soya protein in the finished tube is
lO 4.3% by weight, relative to the cellulose, or 3% by
weight relative to the total weight of the tube.
;~ This corresponds to 86% of the metered-in amount of
~ soya protein.
:~ The peelability of salami, assessed
.. ~7j! 15 analogously to Example 1, is given the value 2.75.
Example 4
10.8 1 of an alkaline solution of the
following composition are metered into 148 l of
alkaline viscose solution:
;~ 20 0.6 kg of wheat protein (~9Amypro SWP,
manufacturer G.R. Amylum N.V.,
Aalst, Belgium)
0.3 l of alkali lye ~4% strength by
weight)
25 0.045 l of glyoxal (40% strength by
weight) and
10.455 l of water.
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The content of wheat protein in the resultant
mixture is 5% by weight.
In order to produce a reinforcement-free
cellulose casing, the viscose solution is extruded in
a known fashion through an annular ring die
~' directly into an acidic precipitation bath and
3 regenerated to form cellulose hydrate gel, and the
tube obtained is washed, plasticized and dried.
The content of wheat protein in the finished
tube is 3.8% by weight relative to the cellulose, or
2.6% by weight relative to the total weight. About
76% by weight of the amount of wheat protein added to
the viscose solution are still present in the
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finished product.
The peelability of a sausage of the scalded
~' sausage type (minced pork sausage) is assessed at 2.
No undesired jelly deposit can be seen between the
casing and the sausage material.
Example 5
~ 20 A fiber-reinforced cellulose skin is produced
: as in ~xample 1. The production process is modified
in that the coagulated tube, which has been
regenerated to form cellulose hydrated gel, is coated
and impregnated on its inside, before drying, with an
additional solution which is present in a tube loop.
This solution has the following composition:
;~1 .
26.54 1 of water
O.3 kg of milk protein (~Rovita FN 4)
1.2 1 of glycerol (plasticizer)
~;! 30 0.127 1 of alkali lye (4% strength by
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weight)
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, 0.023 1 of glyoxal (40~ strength by
i weight) and
i 1.8 1 of triglyceride emulsion based on
~ saturated fatty acids (~Softenol
;,~ 5 special-purpose oil, manufacturer
~ Dynamit Nobel).
The content of milk protein in the finished
product increases to 3% by weight relative to the
-; cellulose, or 2% by weight relative to the total
weight of the casing. The application rate on the
inner surface is 70 mg/m2. The peelability of salami
~'; is assessed at 3.5.
Example 6
The tube of Example 3 is provided analogously
to Example 5 with an additional internal coating.
The peelability of the salami is assessed at 3.
The content of total protein is 4.5% by weight
relative to the cellulose, or 3.1% by weight relative
to the total weight of the tube. The application
rate on the inner tube surface is 60 mg/m2.
In order to determine the application rate for
~ casein, 200 mg of material are scraped from 500 cm2
'~ of the internal tube surface, the nitrogen content is
determined by the method of Kjeldahl, and the amount
of casein is determined from this content.
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` Example 7
18 l of a protein solution adjustedto an alka-
line pH and having the following composition are
~, metered into 125 l of an alkaline viscose solution
having a cellulose content of about 7 % by weight,
upstream of the extrusion die:
40.500 1 of water
4.800 kg of casein ("Saeure-Casein A 110",
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~; manufacturer Meggle, Wasserburg)
2.400 l of soda lye (4 % strength by
weight)
' 0.360 l of glyoxal (40 % strength by
weight)
The resultant mixture has a casein content of
20 % by weight, relative to the cellulose. A paper
web rolled to form a tube is impregnated on theinside
;~ and outside in the weight ratio 7 : 3 with this vis-
cose solution by extrusion dies. Thereafter the tube
is passed in a known fashion through an acidic pre-
cipitation bath and regenerating baths, washed,
treated with glycerol-and then dried in the blown-
up state. The tube has a diameter of 40 ~m.
The casein content of the final tube is 7.6 %
by weight, relative to the total weight, or 17.8 %
by weight, relative to the cellulose. The peelability
of salami is assessed at 2.75, after a maturing time
of 6 weeks.
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