Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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12391
INTRODUCTION
This invention relates to improved food casings
and more particularly to lar~e ~ubular cellulosic food
casings, particularly fi~rous food casin~s,~hich are
..controllabLy moisturized to obviate the need for any
prestuffing soaking, and treated with chloride salts anti
mycotic agents to inhibit the formation and propagation
of mold, ~;east, and bacteria which would otherwise
~end to occur in such moisturized casings.
TYPES OF CASINGS
Artificial food casings used throughout the
world in processing a great variety of meat and other
food products, such as sausages of various types, cheese
rolls, turkey rollsj and the like are customarily pre-
pared from regenerated cellulose a~d other cellulosic
materials. Casings are of several different types and
sizes to accommodate t~e differerLt categories of food
product to be prepared and are provided in supported
or unsupported form, the supported casin~s, commonly
referred to as "fibrous casings", having a fibrous
suppor~ web embedded in the casing wall.
A common feature of many processed food
products, par~iculaxly meat ~roduct~, is that the
mixture o comestible ingredients, commonly called an
"emulsLorl", is stuffed into a casing under pressure,
" 1~70~94 l23gl
and processing of ~he food product is carried out after
its encasement. The food product may also be stored and
shipped while encased in the casing, though in many
instances, and particularly with small sausage prod~cts
such as frankfurtersi the c~sing is removed fro~ the
food product after completion of the processing.
The designation "small food casings" refers
- generally to those casings employed in the preparation
of small size sausage products such as frankfurters.
As the name suggests, this type of foot casing is small
in stuffed diameter, generally having a diameter within
the range of from about 15 mm to about 40 mm, and is most
usually supplied as thin-walled tubes of very great
length. For convenience in handling, these casings,
which may be 20 to 50 meters in length or ~en longer,
are shirred and compressed to produce what is commonly
referred to as "shirred casing sticks" of from about
20 cm to about 60 cm in length. Shirring machines and
the products thereof are shown in U.S. Patent Nos.
2,983,949 and 2,984,574 among others.
"Large size food casings", the common designa-
tion for casings used in the preparation of generally
larger food products, such as salami and ~ologna
sausages, meat loaves, cooked and smoked ham butts and
the like, are produced in stuffed diametèr sizes .of
from about 50 mm to a~out 200 mm or even larger. In
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12391
general, ~uch casings have a wall thickness about three
times greater than "small si7e casings" wall thickness
and are provided with a fi~rous web reinforcement em-
bedded in the wall, though they mæy be prepared without
such supporting medium. Traditionally the large size
subular casings have been supplied to the food processor
in flattened condition, cut to predetermined lengths
of from about 0.6 m to about 2.2 m. Improvements in
shirring and packaging techniques and increased use of
automatic stuffing equipment has increased the demand for
supplying large size casings of both the fibrous and the
unsupported types in the form of shirred sticks con-
taining up to about 30 m and even more of casing.
Large size tubular cellulosic food casings
suitable for use as casings of the present invention
may be prepared by any of several knuwn methods. The
casings are flexible, seamless tubing formed of
regenerated cellulose, cellulose ethers and the like,
and can be prepared by known processes, such as the
cuprammoniu~ process, the deacetylation of cellulose
acetate, the denitration of cellulose nitrate, and
preferably the viscose process. Tubular casings ~~
reinforced with fibers such as, for example, rice paPer
and the like, hemp, rayon, flax, sisal, nylon, poly
ethylene terephthalate and the.~like, are advantageously
employed in a~lications requiring lar~e diam~ter tubular
food casings. Tu~ular fibrous casings can ~e made by
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J 1 ~n~ga 12391
methods and apparatus described, for example, in U.S.
Patent Nos. 2,105,273; 2,144,899; 2,910,380; 3,135,613;
and 3,433,663.
As is well known in the art, tubular cellulosic
casings prepared by any one of the well known me~hods are
generally treated with glycerine, as a humlectant and
softening or plasticizing agent, to provide resistance to
drying or cracking of the casing during storage and
handling prior to stuffing. The glycerine treatment is
usually carried out by passing the casing while still in
its gel state through an aqueous glycerine solution,
after which the plasticized casing is dried to a pre-
determined moisture content prior to further processing
or winding up on reels for storage. Generally, large
size tubular casings will contain about 25% to 35%
glycerine based on the weight of dry cellulose, and will
have a moisture content of about 5% to 10% based upon
total casing weight, prior to being moisturized for
stuffing.
CASING MOIS_URE CONTENT
In the prepara~ion and use of artificial food
casings, particularly small size casings formed of
regenerated cellulose, the moisture content of the
casings is of extreme importance. When small size
cellulosic casings axe made, it is generally necessary
that they be dried to a relatively low water content,
usually in the range of about 10% to 13% by weight,
to enable shirring operations to be carried out
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without damage to the casings. To permit ready
deshirring of the compressed, shirred small size cellu-
losic casing and prevent ~earing and breaking of the
casing during stuffing operations, ~hirred small
casings having an average moisture content of between
about 14% to 13% ~y weight are required. This
relatively narrow range of moisture content is important
because excessive breakàge of the casing during stuffing
has been found to occur at l~wer moisture contents, and
greater moisture content results in excessive plasticitY
of the casing material and overstuffing.
A number of patents have issued in recent
years`dealing with the problem of the moisture content
of shirred small size tubular food casings, and
suggesting various meehods ~or obtaining the desired
moisture level and maintaining it during storage and
shipping. For example, in U.S. Patent Nos. 2,181,32~ to
Hewitt, 3,250,629 to Turbak, and 3,471,305 to Marbach,
packaging means are disclosed which enable a pluralitv
of shirred casing sticks of small size tu~ular casing
to be humidified while packaged. In U.S. Patent Nos.
3,222,192 to Arnold, 3,616,489 to Voo et al,
3,657,769 to Martinek, and 3,809,576 to Marbach et al
various means are disclosed for moisturizing the food
casings befor~ or duri~g the s~irring operation.--
The instant invention is directed to the so-
called. "large s~ ze food casings" which, to stuff pro~erly,
require relatively high moisture content~, generally in
excess of about 20%. Th~ large size food casings are
characterized by relatively thicker wall~ than small
.
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12391
food casings walls and, therefore, require higher
moisture contents to provide the extensibility required
for stuffing operations wi~hout causing undesirable
levels of internal pressure. This invention generally
comprehends the class of casings identified as "large
size food casings", and pa~ticularly those of the
fibrous type.
Large size casings, traditionally supplied in
short lengths of substantially dry flattened tubing are
quitè stiff in the dry state, and are softened for
stuffing operations by soaking in water~ to raise the
moisture content towards or to full saturation. Heretofore
there has been no need to supply such casings with any
predetermined moisture content, and controlled moisturi-
zation by the casing manufacturer in the production of
either short cut lengths or long shirred lengths of the
large size casings has not been warranted. More recently,
however, the wider use of autom tic stuffing equipment
for products utilizing large size tubular food casings
and the increased demand for supplying such cas~ngs in
greater lengths ~n shirred form, a~ compared to the
long used short flat lengths, has emphasi7ed the
problems attending moisturizing such casings by soaking
~ust prior to the stuffing operation. Moreover, the
need for grea~er quality control of all aspects of the
manufacture and use ~f la~ge size food casings has
become increasingly evident. For example, the
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1 1 7~4~ 12391
uniformity of dimensions of stuffed food casings and
food products processed therein has ~ecome increasingly
important commercially, t~e more specifically in further
processes involving automatic weight and slice count
packaging of the product. Casing moisture content has
~een found to be a factor in control of product
uniformity as well as in meeting the need to readily
continually economieally stuff the casings, without
damage or breakage thereof, and with consistently
reproducible results.
Providing shirred small size casings with
the relatively narrow range of uniformly distributed
moisture content required for stuffing operations has
been most efficaciously and economically accomplished
by the casing manufacturer during the fabrication,
shirring, or packaging of the casings. It has become
increasingly evident that the ad~antages of controlled
moisturization enjoyed in the small casings area of the
technology could be re~lized with respect to large
casings if means were developed for the casing manu-
facturer to supply large size casings, ~oth in
flattened and shirred forms, which could be readily
- employed in casing stuffing operations, parti.cularly
substantially fully automated stuffing operations,
without the need for soakin~ procedures just ~rio~ ~o
stuffing and without the need for other undue manual
handling by the food processor.
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l l 70~9d 12391
Althoug~, ~ecause of th univers~l acceptance
of the prestuff~ng soakin~ of large size casings it
has not ~een found necessary in the past for the casing
manufaeturer to maintain the moisture content of large
size food casings wit~in any particular cri~ical sange,
it is ~nown, as ~oted hereina~ove, t~at somewhat higher
~oisture contents are required to afford the desired
flexi~ility of suc~ casings as compared to those
- required for the small size casings. Since greater
amounts of water and consequent increased weight
substantially increases t~e costs of packaging, handling,
storage and shîpping ~he casings, it is important to
moisturize to t~e extent requ~red, ~ut not more than is
necessary.
SPOILA~,~ MICROORGANISM ~ROWTH
.
AnothPr pro~lem whic~ occurs during the handling
and processing of high moisture content large size cellu-
losic food casings involves the growth of mold, yeast,
or bacteria, since high moisture is one of the necessary
factors for inducing such ~r~wth on cellulosic casings.
lt is known for example, that cellulosic food casing5
have a critical moisture content above which the growth of
spoilage microorganism during periods of storage is greatly
enhanced. Generally the critical moisture content is
lower fox mold than for yeast and ~acterîa so that a
moisture content preserving casin~ from mold spoila~e
will also prevent yeast or ~acterial spoilage. Keeping
the moisture content of ~ellulosic casings bel~w a
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12391
~redetermined level, generally below about 20% by weight
of moisture based on the total weight of the casing, has
been fo~nd to be an effective measure to control the
development of such growth. In cases where limitation of
the moisture content cannot be used to inhibit such
growth, such as where higher moisture contents are purpose-
fully provided, or where higher moisture concentrations
may occur in stored casings due to random temperature
differentials across sections of the casing, it is
necessary to provide other means to inhibit the grow~h of
spoilage microorganisms.
Consequently, large size tubular cellulosic
food casings, and particularly tubular fibrous casings,
which may be readil~- stuffed on modern substantially
fully automatic stuffing apparatus, without damage or
breakage, may advantageously be provided with (i) moisture
contents which afford adequate flexibility and obviatP
the n~u for the hit~erto customary soaking step jus~
prior to stuffing, and also with (ii) suitable means for
inhibiting the growth^of molds or o~her microorganisms
during periods of ~hipping, handling, and storage.
The problem of mold growth in food products
due to the presence of nutrients which promote the
gro~th of microorganisms and cause food spoilage has
been the subject of a number of studies over the years.
Various treatments have been e~aluated and recommended,
including combinations of-sugars and polyhydric
alcohols as inhibitors for preventing the growth of
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12391-C
microorganisms commonly recognized as being responsible
for food spoilage. The antimycotic treatment of
cellulose food casings presents additional and more
complex probl~ms due to the processing techniques
employed in the preparation and stuffing of the casings.
Some suggestions for overcoming such problem~ and
; achieving antimycotic treatment of casings usPd for
sausage products or, in some instances, to prevent mold
growth on the sausage product surface after stuffing,
are the subject of several patents. For example, in
U.S. Patent No. 3,617,312 to Rose, an antimycotic agent
is applied to cellulose casings as a component of a
curable water-insoluble coating, and in U.S. Patent
3,935,320 to Chiu et alJ cured water-insoluble cationic
thermo-setting resin coatings applied to the surfaces
of casings reduce deterioration wrought by enzymatic
action. The Canadian Patent No. 1,0969230, issued
February 24, 1981, discloses the antimycotic treatment
of controllably moisturized casings with aqueous solutions
of various agents including, amongst others, propylene
glycol and the propionates and sorbates of potassiu~,
sodium and calcium.
An important distinction to be noted with regard
to these aforementioned references is that the '312 patent
is directed to preventing mold growth on the sausage
product surface after stuffing and is not concerned with
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11 7~494 12391
preventing the growth of spoilage microorganisms in th~
sausage casing prior to stuffing, as is the present
invention.
The inclusion of moisture in the casing to any
extent gives rise to the consideration of, among other
things, the phenomenon ~nown as "water activity". Water
activit~ represented by the symbol ~w~ is defined as the
ratio of the partial vapor pressure of water in a solu-
~ tion to the vapor pressure of pure wa~er, both measured
10 at the same temperature. It is used in connection with
describing the present invention to the extent that it is
a convenient and useful parameter to quantify the moisture
levels in the casings treated with chloride salts according
to the technique of the invention. Convenient litera~ure
references treating the water activity phenomenon in
greater detail are to be found in Ross, Estimation of
Water Activity In Intermediate Moisture Foods, Food
Technology, March 1975, page 26, and in 41 Journal of
Food Science, page 352, May-June 1976.
The present invention is based on the use of
chloride salts, along with preselected amounts of mois-
ture added to the casing being prep red according to the
invention, to controllably lower the water activity, Aw ~
to a level, commensurate with the particular moisturiza-
tion level of a given casing, at which mold growth will
be inhibited for as long a she~lf ~ife as the c~sing may
be expected to have.
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In general, the invention comprehends a large
size tubular fibrous reinforced cellulosic food casin~
which is premois~urized by adding carefully controlled
amounts of moisturizing water to ~he extent that the
casing can be stuffed withou~ the necessity of any pre-
stuffing soaking. The controllably added moisture may
vary from as low as about -20% to as high as about 40/O of
the total weight of the casing. A preferred range of
moist~re content in the casings is from about 20% to about
25%. A chloride salt selected from the group consisting of
sodium chloride, magnesium chloride, ammonium chloride,
calcium chloride, and potassium chloride, is added, prefer-
ably by inclusion in the moisturizing water, and the solu-
tion is applied to the casing by any of several known
methods, such as spraying or by slugging or a combination of
these for instance. The particular chloride salt used, the
target moisture level selected for the casing and, to some
extent the projected shelf life of casing, d~termine the
salt concentra~ion required to maintain the water activity,
Aw~ in the casin~ at a~value low enough, p_~ferably not more
than about 0.75 ~o insure agains~ mold growth.
Sodium chloride has been found to be most effective,
in that relatively small quantities, from about 2% to about
22.6% of the weigh~ of cellulose in the casing, will pro~ect
against mold growth in casings wi~h mois~ure contents of from
about 20% to about 40% of ~otal casing weight by maintaining
the casing Aw at about 0.7~. In addition, odium chloride
is a normal constituent of processed foods and is a readily
accept~d addition to casings.
I 17~494 12391
~ ligher concent~ations of the other chloride
salts are required to effect mold inhibition in casings
similarly moisturized by keeping the Aw at not more than
about 0.75: magnesium chloride from about 2.9% to about
22.0C~; a~monium chloride from about 3.1% to about 33.2%;
calciu~ chloride from about 4.1% to about 35.9%; and
potassi~m chloride from about 2. 6% to about 68.7% of the
weight of cellulose in the casing to produce the same
~eneral over-range results.
~X~LE I
In order ~o demonstrate the effectiveness of
sodium chloride in mold growth inhibition a culture dish
mold growth test was conducted.
A conventional potato-dextrose agar solution
was used as the base media into which was incorporated
various proportions of the sodium chloride and polyol.
The agar and salt and polyol co~ponent solutions were
sterilized and tartaric acid added to combined solutions
to obtain a pH of about 3.5 in the final agar media.
The mold cu~ture used as the inoculant in this
test was prepared as follows:
A mixture containing thirty-one different mold
spores in a 1% sodium citrate solution was prepared
using conventional aseptic procedures with a con-
centration of about l ~o 5 million mold spores per
milliliter of solution. Among the mold cultures
included in the mixture were Asper~illus niger
(ATCC #1004), Chaetonium Rlobosum ~ATCC #l~
Memnoniella ec~inata (ATc~ Ig73~ Myro~hecium
- 30 verrucaria (ATCC ~gO95), Trichoderma viri~ ATCC
~26921~, and Whetzelinia ~ e ~ #18657),
all of which were purchased ~rom American Type
Culture Collection, Rockville, Maryland. Also
included were mold spores of nine mold cultures
that were isolated from mold contamination found
on various cellulosic food casings, and mold
spores of six~een ~o-ld cultures that were isolated
as naturally occurring airborne contæminants
obtained from wi~hin casing manu~acturing SitQs.
.
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117049~ 1 391
Test solutions of the agar medium and mold
inoculum were prepared with sodium ehloride and propyle~e
glvcol separately, and in cross-combined variations in
concentrations of 0%, 2.5%, 5~0, 7~5b/o~ 10%, 12.5%, and one
of 15% propylene glycol only, by to~al weight of test
.~ solution.
The test solutions were stored in covered
dislles for seven days a~ ambient temperature and visually
inspected for mold growth.
Table 1, below illustrates the results of the
- test.
Table 1
CULTURE DIS~ ,IOLD GRO~H STUDIES - EFFECT OF
SALT AND PROPYL~NE GLYCOL
.
NaCl Propylene Glycol Concentration (%)
Concentr,ation 0 5 7 5 10 5
O ~ + + + +
2.5 + + ~ + _ _
5.0 + + +
7.5 + ,+ - _ _ _
10. 0 + _ _ _ _
12.5 +
Blank Negative Control = No Growth.
Key: + = Mold growth present
- - Mold growth inhibi~ed
These test results ~how tha~ sodium.chloride,
has discernible mold inhibiting properties when present
in re,latively small ~uantities with another antimycotic
agent, in this instance, propylene glycol.
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~ ~ 7049~
EXA~PLE II
This example demonstrates that sodium chloride
in a concentration as low as 4% and calcium chloride at
7% of casing cellulose content are effective antimycotic
agents for fibrous casings with moisture contents o
above about 30% of total casing weight.
This example also shows that casings containing
glycerol and water can be preserved against mold
spoilage if the water activity, A~, is controllably
reduced by the incorporation into the casing of chloride
salts. Thus a relatively highly moisturized large size
fibrous cellulosic casing, containing moisture sufficient
to stuff the casing without pre-stuffing soaking or the
further addition of moisture in any manner, can be made
shelf-stable and antimycoti~ally pro~ected by means of
salt additives.
In preparation for the experimental work for
this Example, a number of pieces o size 8 shirred tubular
fibrous cellulosic sausage casings having a maximum
stuffing diameter of 4.96 inches, or 12.1 centimeters,
with the proportions of ingredients shown in Table 2,
below were prepared by unreeling the casing lengths
from a reeled flat width supply, introducing the salt
by slugging the casing with a salt solution, and
raising the moisture content to the target level by
spraying water on the outside surface of the casing just
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prior to shirring it. The glycerol levels in these
experimental casing samples were identical to the levels
of glycerol included as a softener in conventional fibrous
cellulosic casing which must be soaked in wa.er prior to
stuffing~ No propylene glycol was included in any of
. these sample casings of this Example.
Table ?
Mold Growth Observations on Hi~h
Moisture Content Fibrous Celluisic_Sausa~e
Casin~s Preserved T~i~h~Chloride Sal;s
CasinO Glycerol Moisture ~ oride Salt Calculated Visi~le
Sample (% of (~tOof total ~ e Am~unt water mold
cellu- casing ~/~of activity gro~.ha
lose) weight) cellu- (Aw)
lose) no salt
s~lt added
added
A 29.0 42.7 none 0 0.91 0.91 +
B 27.0 33.3 NaCl 4.4 0.90 0.86
C 30.~ 32.3 NaCl 4.1 0.89 0.84
D 2~.5 39.4 NaCl 7.9 0.90 0.83
E 29.7 38.4 NaCl 9.4 0.90 0.81
F 30.6 33.6 NaCl 8.4 0.89 0.80
G 30.6 31.7 N~51 8.8 0.89 0.78
H 25.1 39.1 NaCl 18.1 0.91 0.77
1 28.8 32.8 NaCl lS.l 0.90 0.73
J 32.9 34.0 CaC12 16.5 0.90 ~.79
a. After3 nonths at 35C:
+ = visible mcld growth
- = nD visible m~ld gr~
Casing samples used in the experiment of this
Exa~ple were shirred and compressed to make 175 feet
(53.34 ~eters) casing lengths into 24 inch (61 centimeter)
stick lengths which were re~ained in elastic sheathing
overwraps.
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Mold inoculant for this experiment was prepared
as follows:
Five separate suspensions of mold inoculant were
used. Aspergillus n ger, (A~CC #1004) As~erillus
glaucl~s, Geotricum candidum, and a Penicilliu~.
moLd species found in high moisture casings, were all
used separately and then all added to an addit:ional
mixed suspension containing Chaetoniu~ ~lobosu~.
(ATCC #16021), ~Iemnoniella echina~a (ATCC j;ii9/3),
Mvrothecium verrucaria (ATCC ~9G95), Trichoderma
viride ~ATCC ~26921), and .~~etzelinia_sclerotiorum
(ATCC #18657). Also included in this fifth inoculant
werD mold spores of nine mold cultures which had been
isolated from mold contamination found on various
cellulose food casings, and moId spores of sixteen
mold cultures isolated from ambient airborne con-
taminants obtained at casing manufacturing loca~ions.
The suspensions contained one to five million
colony forming units per milliliter of 1% sodium citrate
and were pr~pared uslng conventional aseptic procedures.
The cultures identified by the "ATCC" designa-
tions were purchased from the American Type Culture
Collection, Rockville, Maryland.
The casing samples wer~ inoculated by brushing
several milliliters of each of the above-described mold
suspensions in 1/2 inch (1.27 centimeter) strips of
shirred surface along the length of each shirred stick.
Each of the five mol~ suspensions was inoculated into a
separate strip on one shirred casing length. After
inoculation each inoculated casing was cut into five
slices perpendicular to the shirred stick length. Each
slice was placed in a,separate one-quart wide-mouth
canning jar which was closed and stored at a constant
35C. The mold growth results are shown in Table 2,
above. Results wererecorded as positive (+) if visible
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- I 17~494 12391
mold growth appeared i~ any one of the five areas where ~he
separate mold suspensions had been inoculated, and negative
(-) if mold growth was not visible in any of ~he inocl-lated
areas.
The results in Table 2 show that casing sample A,
the only sample ~ith no salt at all included as an anti-
mycotic, was ~he only sampie which had visible mold growth
within three months. Casing samples B through I, all of
which had sufficient sodium chloride, NaCl, added as an~i-
mycotic, did not show visible mold growth within threemonths. The incorporation of the sodiun chloride in
casings B through I reduced the water activity, Aw, in
these samples from what it would have been if no salt
had been added, from 0.89 to 0.91, at which ~alues mold
growth would occur, down to 0.73 to 0.86, values where
no mold growth occurred within three month~.
Casing sample J had calcium chloride incorpor-
ated as an antimycotic an~ did not show visible mold
growth. The calcium chloride in the J sample reduced the
water activity, Aw, from 0.90, where mold growth would be
expected, down to a value of 0.79 where no mold growth
occurred.
The example shows that large size high moisture
fibrous ~ausage casings can be pxeserved by the incor-
poration of relatively small amounts of chloride salts.
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12391
EXA~LE III
This example involved experimental work perfor~ed
to show that chloride salts other than sodium chloride can
be used as antimycotics for high moisture large si7e
fibrous cellulosic sausage casings.
Basic data calculations were made according to
known methods to establish the relationship bet~een salt
content and water activi~y, Aw, and the water activity,
Aw, also determined experimentally where necessary. The
relatîonships were used to calculate the amounts of the
` various chloride salts required to preserve high moisture
fibrous sausage casings, based upon the assumption,
supported by other experimental work done on this inven-
tion, that a water activity, Aw, o 0.75 will indicate
effective antimycotic protection of the casing.
In the conduct of the experimental work of this
example the solutions of the chloride salts MgC12,
NH4Cl, and CaC12 had their water acti~ity, Aw, values
deter~ined by measuring RH with a Sina moisture sensor,
and the water activity values for the KCl and the NaCl
solutions were included as reported by Sloan and Labuza,
Food Product Development, December, 1975, page 6~.
Drawin~ Fi~ure 1
The data was plotted on Cartesian coordinates
as a family of curves, each curve representing one of
the chloride salts, showing the relationship between the
water activity, Aw, and ~he water to salt ratio expressed
in grams of water per lO0 grams of anhydrous solid salt.
Figure 1 of-the drawing sho~ this plot~ed data.
.
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I 1 70494
12391
Using drawin~ Figure 1, ~he known composition
of fibrous sausage casing and the water activity, ~ ,
calculation method described by Ross, the amount of each
chloride salt required to preserve high moisture fibrous
casing for various moisturejlevels and 33% glycerine was
calculated. The calculations werP. based upon the use of
a single chloride salt in each case, and the assumption
that a water activity, ~w, of 0.75 will be low enough to
preserve the casing during ten months of storage at 35C.
Table 3, below, summarizes the calculations of
this Example.
Table 3
Casing Chloride Salt Content Required To
Reduce Casin~ Water Activlt r, Aw,_To
A Casing Preservation Value o Aw = 0.75
Target Casing Chloride Salt (weiy~t 7/~ of cellulose)
casing ~ater reql;red to reduce ~ing ~1 water
moisture Activity activity to kw = 0.75 _ _
~/Oof to~al Wi~Ut
casing ~ei~ht) salt NaCl ~ 2 NH4Cl CaC12 X~l
0.79 2.0 ~.9 3.1 4.1 2.6
0.83 5.~ 6.7 8.0 9.7 8.3
Q.~7 ~ 10.4 11.3 1~.7 18.~ 21.0
0.90 . 2~.6 22.0 33.2 35.9 68.7
The data of Table 3 shows that the amount of
chloride salt required to preserve a high moisture
fibrous sausage casing, capable of being stuffed without
the addition of any further pre-stuffing soaking or
moisturization, depends upon the moisture content of the
casing. Generally about 20% to 25% moisture by ~otal
casin~ weight has been found to be the practical moisture
. ~
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1170~9~ 12391-C
content range for large size fibrous cellulose casings
to be used without further pre-stuffing soaking or
moisturization.
The amount of chloride salt required for casing
preservation from mold growth, it can ~e seen from the
tabulated data in Table 3, differs according to which of
the various chloride salts of this Example is used. It
is noteworthy that less sodium chloride is required for
antimycotic effect than is the case with other chloride
salts. ~s little as 2% by weight of casing cellulose is
required to preserve casing with a moisture content of
20%. By way of contrast, it is seen that larger amounts
of other salts are required for casing preservation. It
can be seen that at the moisture range of about 20% to
25% and with the preferred chloride salt, sodium chloride,
of 2.0% to 5.4% sodium chloride by weight of casing
cellulose is required for casing preservation.
EXAMPLE I~
An experiment was conducted to compare the
practical working utility of a tubular fibrous cellulose
casing prepared according to this invention, containing
5% sodium chloride and 25% moisture to an identical
casing containing propylene glycol as an antimycotic
agent, prepared in accordance with the invention of
Canadian Patent No. 1,096,230, issued February 24, 1981.
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. ~17n494 12391
In preparing the salt protected casing sample,
a reel length of size 4 tubular fibrous cellulosic sausage
casin~ having a maxim~m stuffing diameter of 3.26 inches
(8.28 centimeters) was treated with an 8.8% sodium chloride,
2% glycerol, 89.2% water ~olution to give casing target
values of 5% sodium chloride by weight of cellulose, and
25~ moisture on a total casing weight basis.
The casing samples A and B for this example were
shirred, compressed to give 175 feet (53.34 meters~ of casing
in a 24 inch (61 centimeters) stick length, and encased in
an elastic sheathing mater$al. A plastic sizing disc was
inserted in one end of each shirred length and that end
closed with a metal clip. The behavior of the two samples
during shirring, compression, covering with the elastic
sheaths, sizing disc insertions, and the clipping, was
identical.
The sodium chloride, propylene glycol and moisture
content of L hP two sample casings A and B are summarized
below in Table 4.
, Table 4
Com~osition of Casin~ Samples
Cont ning Sodium Chloride ~
Propylene Glycol As Antimycotic A~ents
Casin~ ComPoSitiOn
Sodium Water GIycerol ~ropylene
Chloride (% of (% of Glycol
(% of Total Cellulose~ (~/O of
CasingCellulo_e~ Casing Cellulose~
SampleWei~ht)
A 4.9 25.5 .39.3 . .0
B 0 24.0 37.9 7.2
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1~70494 123gl
The sample casings of this Example were next
stuffed with bologna sausage e~ulsion on an automatic stuff-
ing machine. Stuffing performance of the two samples was
identical. The diameters of the sausage lenvths stuffed
using the salt A casing were iden~ical to the dia~.eters of
the prop~lene glycol B casing ~easured both before and after
smokehouse processing of the products. The color and
appearance of the A and B~casing sausage samples was also
identical.
L0 This Example shows that a shirred fibrous sausage
casing containing 5~/~ sodium chloride by weight of casing
cellulose and 25C' moisture by total casing weight is as fully
functional as similar casing containing propylene glycol as
an antimycotic agent, in modern stuffing equipment for large-
size sausage products where casing is stuffed without any
pre-stuffing soaking~
EX~PLE V
This example shows that chloride salt applied ~o
the inner surface of a fibrous cellulosic sausage casing
migrates through the wa~l of the casing and is detected at
the outside surface of the casing. Such migration of
chloride salts is necessary if the salt is to be applied
to one surface and prevent mold growth on both surfaces.
In the conduct of this example, a 33 inch piece
of size 2~ fibrous sausage casing having a moisture content
of 6% of the ~otal casing weight had its internal surface
treated with 75 milliliters of a satura~ed sodium chloride
solution by a slugging technique. The casing was opened
and the 75 milliliter salt solution slug wa~ allowed to
.
contact all portions of the interior surface for a brief
perio~ of ~me after which the excess salt solution was
. .
discarded.
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~1 7Q49~ 12391
At ineervals after slugging, the outside surface
was tasted with the tongue and the taste ser.sarion ~:~s
recorded. At each time interval, a different portion of
the casing surface was tasted. The resul~s are shown in
Table S.
Table 5
.. ' Mioration of Sodium Chloride
From Interior Casin~ Surface
To External Casin~ Surface
Time (seconds) after
slugging the internal
casing surface with Taste of the external
saturated salt solution casing surface
Sweet only, no salt
Sweet only, no salt
More sweet than salè
~ore sweet than salt
More sweet than salt
~lore sweet than salt
~0 100 ~Iore saLt ehan sweet
120 More salt than sweet
150 Salt only, no sweet
180 Strong salt only, no sweet
This example demonstrates the mi~ration to the
external surface of a casing of an internally applied
saturated sodium chloride solution. In the first 20
seconds after applying the salt solution, only the sweet
taste of glycerol could be detected at the casing external
surface. From 30 to 80 seconds salt could be detected in
the presence of a stronger sweet taste of glycerol. From
80 to 120 seconds the salt taste was stronger than the
sweet glycerol taste. At 150 seconds the salt taste was
so strong that a sweet glycerol taste could no lo~ger be
detected. At 180 seconds, the salt taste was even stronger.
After 180 seconds the casing was split so tha~ the internal
surfac~, as well as the external surface, could be tasted.
Both the internal surface and the external surface had
identical strong salt tastes which masked any sweet
glycerol tast~.
~1 1 7049~
12391
Thus salt applied to the internal casing surface
is readily detected at the external casing surface and
could thus prevent mold ~rowth at both casin~ surfaces.
E~A~LE VI
This exa~ple shows that the incorporation of
chloride salts into high moisture fibrous cellulosic sausage
casing has no deleterious effect on the burst strength of
the casing.
During manufacture of fibrous rellulosic sausage
casings, extensive washing is performed on the casing prior
to drying. One purpose of this wash step is to remove
sulfate salts from the gel casing. Such salts, prior to
the time of this invention, had been regarded by those
skilled in the art as probable contributing factors in
reducing the strength of the oasing. This Example shows
that no undesireable strength reduction results from the
incorporation of chloride salts as an antimycotic into high
moisture fibrous cellulosic sausage casings capable of
being stuffed without further prestuffing soaking in water
or any form of moistur,e addition.
In the preparation of this example, fibrous
casings from Examples II and IV were selected for measure-
ment of the burst pressure. The ca~in~s were inflated with
air and the pressure recorded when the casings burst. The
sesu}ts are shown in Table 6, below.
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Table 6
Effect of Chloride Salts on
Burst Pressure of Hi~h Moisture
No-Soak Fibrous Cellulosic Sausa~e Casin~s
Salt
A~ount Burst
`Casing t% of Pressure
Sam?le TypeCel~ulose) (mm ~rc~ry)
IIA None 0 530
IIE NaCl9.4 534
IIH NaCl18.1 515
IIJ CaC1216?5 522
IVA NaCl4.9 771
IVB None 0 745
Casings IIE, IIH, IIJ, and IVA, which contain
chloride salts, have burst pressures not significantly
different from control casings IIA and IVB which contain
no chloride salts. The vir~ually identical observ4d
burst pressures indicate no detrimental effect of chloride
salts on casing strength. The test samples showed no
indication of embrittlement of the casing due to the
presence of chloride salts.
EXAMPLE VII
This Example shows that preservation of high moisture
no-soak fibrous casings from mold spoilage obtains when a
chloride salt antimycotic solution is added directly to
the bore of shirred casing. Effective preservation is
attained in spite of an observed non-uniform application
of the salt antimycotic solution. The direct addition of
antimycotic to shirred casing contras~s to the customary
method of addition by uniform imbibition of the solution
onto th~ casing prior to shirring, and ~hus provides an
alternative mode of practicing the invention.
_ -27-
11 7~494 12391
In the preparation of casings for this EY.ample~
six-inch shirred lengths of size 8 shirred tub~lar fibrous
cellulosic sausage casings having a maximum stuffing
tiameter of 4.76 inches ~12.1 centimeters), a moisture
content of 12% of the total casing weight, and a glycerol
content of 29.5~,' of the casing cellulose were used. To
prepare casings of varied ~oisture and chloride sal~ con-
tents, the test solutions~were added to the bores of the
shirred casings. The addition was made as uniformly as
possible throughout the lengths of the shirred casing and
the casing was rotated about its longitudinal axis after
the addition to permit the solution to soak into the casing
as uniformly as possible. With all of these precautions,
nevertheless, a tendency for the solution to "pocket" or
collect in shirring folds was noted.
After a four week equilibration period in a
plastic bag, the casing samples were inoculated with mold
cultures, subdivided, stored at 35Cj and v~_rved for
visible mold growth as described in Example II, above.
It was observed that the mold ~rowth results in
this Example, as shown in Table 7, below, are comparable
and consistent with those reported in Example II where salt
solution was applied uniformly to the casing surface prior
to shirring. Casing sa~ple A, which had no added salt
antimycotic, had visible mold growth due to its high water
activity of 0.89. Casing sample B, which ~lso had no addet
salt, did not show mold growth due to its lower water
activity of 0.84. Casing samples C through G contained
salc antimycotic and did not show mold growth due to their
.
low water activities. The observed non-uniform addition
.
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117n~94 12391
of salt antimycotic solution by direct addition ~o the bore
of shirred casing did not influence internretation of ~he
mold growt~ results in terms of casing water activitv.
Thus, non-uniform addition of chloride salt solution does
not prevent the chloride salt from acting as an antimYcotic
for no-soak casin~.
Table 7
Preservation o~ No-Soak Ca_ing
BY Addltion o~ ~cdium Chloride Salt
Solu_ion to the ~ore of Shirred ~asin~
Visible
Casin~ Variables _ ~old
'' '~~' Sodium ~rowth
Moisture ~lycerol Chloride Calculated After 13
Casin~ o.f (% of Salt (,, of Water ~onths
Sample Total) Cellulose) Cellulose) Activity At 35'C
A 34.0 29.5 0 0.84 +
B 24.0 29.5 0 0.84
C 34.0 29.5 5.9 0.83
D 24.0 29.5 2.4 Q.80
E 34.0 29~5 9.8 0.79
F 24.0 29.5 4.5 0.78 -
34.~ 2g.5 14.4 0.76
EXAMPLE VIII
This Example involved reexamination of the Example
II casings, which were exEmined for mold growth after three
(3) months storage at 35~C, at later periods of time, cix
(6), eight ~8), and ten C10) months. Table 8, belo~, shows
the listing of the identical casin,~ samples of Ta~le 2,
Example II, all of the other tabulated values of Table 2
being the same of this~Example as in Example II, with the
visible mold growth results tabulated for the addition~l
time periods as well as reproduced for the ori~inal three
(3) mohth period.
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7n4g~
12391
Table 8
Periodic ~fold Growth Observations
On Hi~h ~loisture Fibrous Cellulosic
~ Sausa~e Casin~s Preserved
With Chlorlde Salts
Calculated
Water
Activity
No Aw salt
Casing salt addPd Visible Mold Growth at
Samp~e added 3 m~s. 6 mos 8 mos. 10 mos.
.
A 0.~1 0.91 ~ ~ + +
B 0.90 0.86 ~ - ~ +
C 0.89 0.84 - - - -
D 0.90 0.83
E 0.90 0.81 - - - -
F 0.89 0.80 - - - -
G 0.89 0.78 - - ~ -
H Q.91 0.77
I 0.90 0.73 _ _ _ _
J O~ 90 0. 79 ~ ~ r
a. At 35C
- visible mold growth
- = no visible mold ~rowth
Table 8 shows that chloride salts prevent or
delay mold spoilage of high moisture fibrous cellulosic
sausage casing. Generally, a delay in mold spoilage
occurred with chlorite salt-containing casi~gs with water
acti~ity Aw values of 0.83 and above. Salt-containing
casings with Aw values of 0.81 and below were preserved
for the entire 10 month storage period. Casing A in Table
8 had visible mold growth appear after 3 months storage
because no chloridP salt was added as an antimycotic. Chloride
~alt ant~mycotic added to Casin~ B reduced the Aw..tu 0.86
and delayed the appearance of visible mold growth
until eight months of s~orage time. Chloride salt
sntimycotic added to Ca~ing D reduced the Aw further to
_ ~30~
,~, . .
1 1 7n4s~
12391
0.83 and also caused a delay in the appearance of visi~ble
mold growth to 8 months storage. Casin~ C, with salt anti-
mycotic added to give an Aw of 0.84, did not show visible
mold ~rowth at 10 months-stora~e although Casing D with a
lower Aw of 0.83 showed visible mold growth. This indicates
that an Aw of 0.~4 is sufficiently close to the minimu~
value permittin~ mold growth that visible mold growth may
fail to appear. Casings E through I did not show ~isible
mold growth even after lO months storage because of the
addition of sufficien~ chloride salt antimycotic to reduce
the AW to 0.81 or below.
EX~IPLE IX
This example demonstrates that a ~asing water
activity not exceeding about 0.75 is preferred where long
term storage is required under commercial conditions of
fluctuating temperatures. This example invol~es further
reexamination of the casings described in Example II and
in Example VIII.
Mold growth visible to the unaided eye was fo~nd
unexpectedly after 1~ months storage in salt antimycotic
casings with as low as a 0.73 water activity (Sample I).
These casings were stored uninoculated in a store room
having fluctuating room temperatures which ranged from
about 65 to 80F (about 18 to 27C). Constant ~emperature
35C storage of inoculated samples from the same casing
series did not show mold growth until a water activity of
0.83 was reached (Sample D). Conceivably1 temperature
fluctuations caused moisture vapor migration from warmer
areas of the casing to the cooler areas, thus raising the
water activity of one axea of the casing sufficiently to
permit mold growth. The mold gro~th results sre shown in
detail in Table 9.
. ~ , .
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1 1 7n4~
12391
Table 9
Mold Growth Observations On
Hi~h ~oisture Fibrous Sausage
Casings Preserved ITith Chloride Salts
Cal~ated
Water
Activity
~oride salt (~ Visible~ld
Mbis~e~ e ocount if no Wn~lGr~,~h(b)
Glycerol ~/Oof ~/Oof salt salt After After
~ing ~/0of Total Cellu- added is 12 432
Sa~?le Cellulose) Wei~ht) lose) added M~nths Mbnths
A 29.0 42~7 None 0 0.91 0.91 (c) +
B 27.0 33. 3 ~aCl4.4 0.90 0.86 + +
C 30.8 32.3 ~aCl4.1 0.89 0.84
D 28.5 39.4 NaCl7.9 0.90 0.83 +
E 29.7 38. 4 Næl 9.4 0.30 0. 81 +
F 30.6 33.6 'laCl8.4 0.89 0.80
G 30.6 31.7 NaCl8.8 0.89 0.78
H 25.1 39.1 NaCl18.1 0.91 0.77 - -
28.8 32.8 NaCl18.1 0.90 0.73 ~ -
~) ~ ~ stored u~culated at fluctuating room t~erature
(c) Observation not made
The preferred mode of practicing the invention
is to use about 2% to 10% sodium chloride concentration
by wei~ht of cellulose in the ~a~ing, in combination ~ith
a casing moisture content of about 20% to 25% of the total
casing weight, adjusting.these parameters to attain a final
calculated casing water Activity, Aw, of about 0.75 or
lower.
The foregoing description and examples and the
experimental da~a therein show that chloride salts are
effective antimycotic agents in large size fibrous cellu-
losic sausage casings, and can be successfully used in
place of heretofore used large quantities of expensive
softeners. The use of chloride salts as antimycotics
rather than.the known and presently used softeners, such
.
_ --32--
~704~ 12391
as, for instance,propylene glycol, not only provides an
econo~ic advantage to the casing producers and users, but,
in some countries, particularly some European countries,
overcomes the regulatory control or prohibition of the use
of polyol softeners. Food ~aws in some countries closely
control the use of polyol so'teners and in some European
countries, the use of the-so~tener propylene glycol is
not approved for use in food packaging. In some instances,
the quantity of glycerol permitted is so low that it cannot
be relied on for preservative effect in high moisture
fibrous cellulosic casings.
These then are ~he problems overcome, the advan-
tages provided, and the novel and advantageous features of
this invention. The foregoing description of the invention
is intPnded to be illustrative only and should not be con-
strued in any limiting sense.
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