GB2071988A - Cellulosic food casings - Google Patents

Abstract

Large size tubular cellulosic food casings used in making stuffed food products such as large sausage products, encased processed meat products and rolled meat products, are moisturized to e.g. 20 to 40% moisture content, which permits elimination of any further pre-stuffing soaking and are treated with chloride salts to maintain the Aw below 0.81 and thus inhibit mold, yeast, and bacterial growth prior to stuffing the casing with foodstuff.

Description

SPECIFICATION Cellulosic food casings This invention relates to improved food casirigs and more particularly to large tubular cellulosic food casings, particularly fibrous food casings, which are controllably moisturized to obviate the need for any prestuffing soaking, and treated with chloride salts antimycotic agents to inhibit the formation and propagation of mold, yeast, and bacteria which would otherwise tend to occur in such moisturized 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 rolls, and the like are customarily prepared from regenerated cellulose and other cellulosic materials. Casings are of several different types and sizes to accommodate the different categories of food product to be prepared and are provided in supported or unsupported form, the supported casings, commonly referred to as "fibrous casings", having a fibrous support web embedded in the casing wall.

A common feature of many processed food products, particularly meat products, is that the mixture of comestible ingredients, commonly called an "emulsion", is stuffed into a casing under pressure, and processing of the 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 products such as frankfurters, the casing is removed from 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 food 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 even 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 designation for casings used in the preparation of generally larger food products, such as salami and bologna sausages, meat loaves, cooked and smoked ham butts and the like, are produced in stuffed diameter sizes of from about 50 mm to about 200 mm or even larger. In general, such casings have a wall thickness about three times greater than "small size casings" wall thickness and are provided with a fibrous web reinforcement embedded in the wall, though they may be prepared without such supporting medium. Traditionally the large size tubular 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 containing 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 known 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 cuprammonium 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, polyethylene terephthalate and the like, are advantageously employed in applications requiring large diametertubularfood casings. Tubular fibrous casings can be made by methods and apparatus described, for example, in U.S. Patent Nos. 2,105,273; 2,144,899; 2,910,380; 3,135,613; and 3,433,633.

As is well known in the art, tubular cellulosic casings prepared by any one of the well known methods are generally treated with glycerine, as a humectant 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 predetermined 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.

In the preparation 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 are 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 without damage to the casings.

To permit ready deshirring of the compressed, shirred small size cellulosic casing and prevent tearing and breaking ofthe casing during stuffing operations, shirred small casings having an average moisture content of between about 14% to 18% by weight are required. This relatively narrow range of moisture content is important because excessive breakage of the casing during stuffing has been found to occur at lower 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 methods for obtaining the desired moisture level and maintaining it during storage and shipping. For example, in U.S. Patent Nos. 2,181,329 to Hewitt, 3,250,629 to Turbak, and 3,471,305 to Marbach, packaging means are disclosed which enable a plurality of shirred casing sticks of small size tubular 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 before or during the shirring operation.

The instant invention is directed to the so-called "large size food casings" which, to stuff properly, require relatively high moisture contents, generally in excess of about 20%. The large size food casings are characterized by relatively thicker walls than small food casings walls and, therefore, require higher moisture contents to provide the extensibility required for stuffing operations without causing undesirable levels of internal pressure. This invention generally comprehends the class of casings identified as "large size food casings", and particularly those of the fibrous type.

Large size casings, traditionally supplied in short lengths of substantially dry flattened tubing are quite 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 moisturization 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 automatic stuffing equipment for products utilizing large size tubular food casings and the increased demand for supplying such casings in greater lengths in shirred form, as compared to the long used short flat lengths, has emphasized the problems attending moisturizing such casings by soaking just prior to the stuffing operation. Moreover, the need for greater quality control of all aspects of the manufacture and use of large size food casings has become increasingly evident. For example, the uniformity of dimensions of stuffed food casings and food products processed therein has become increasingly important commercially, the more specifically in further processes involving automatic weight and slice count packaging of the product.Casing moisture content has been found to be a factor in control of product uniformity as well as in meeting the need to readily continually economically 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 advantages of controlled moisturization enjoyed in the small casings area of the technology could be realized with respect to large casings if means were developed for the casing manufacturer to supply large size casings, both in flattened and shirred forms, which could be readily employed in casing stuffing operations, particularly substantially fully automated stuffing operations, without the need for soaking procedures just prior to stuffing and without the need for other undue manual handling by the food processor.

Although, because of the universal acceptance of the prestuffing soaking of large size casings it has not been found necessary in the past for the casing manufacturer to maintain the moisture content of large size food casings within any particular critical range, it is known, as noted hereinabove, that somewhat higher moisture contents are required to afford the desired flexibility of such casings as compared to those required for the small size casings. Since greater amounts of water and consequent increased weight substantially increases the costs of packaging, handling, storage and shipping the casings, it is important to moisturize to the extent required, but not more than is necessary.

Another problem which occurs during the handling and procesing of high moisture content large size cellulosic food casings involves the growth of mold, yeast, or bacteria, since high moisture is one of the necessary factors for inducing such growth on cellulosic casings. It is known for example, that cellulosic food casings 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 for mold than for yeast and bacteria so that a moisture content preserving casing from mold spoilage will also prevent yeast or bacterial spoilage.Keeping the moisture content of cellulosic casings below a predetermined level, generally below about 20% by weight of moisture based on the total weight of the casing, has been found 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 purposefully 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 growth of spoilage microorganisms.

Consequently, large size tubular cellulosic food casings, and particularly tubular fibrous casings, which may be readily 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 obviate the need for the hitherto customary soaking step just prior to stuffing, and also with (ii) suitable means for inhibiting the growth of molds or other microorganisms during periods of shipping, handling, and storage.

The problem of mold growth in food products due to the presence of nutrients which promote the growth of microorganisms and cause food spoilage has been the subject of a number of studies over the years.

Various treatments have been evaluated and recommended, including combinations of sugars and polyhydric alcohols as inhibitors for preventing the growth of microorganisms commonly recognized as being responsible for food spoilage. The antimycotic treatment of cellulose food casings presents additional and more complex problems due to the processing techniques employed in the preparation and stuffing of the casings. Some suggestions for overcoming such problems and achieving antimycotic treatment of casings used 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 al, cured water-insoluble cationic thermo-setting resin coatings applied to the surfaces of casings reduce deterioration wrought by enzymatic action. The copending application of Ellis and Chiu, Serial No. 014,644, filed February 23, 1979, and assigned to the same assignee as this application, 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 potassium, sodium and calcium. Our own copending Serial No. filed 1980, relates to the use of extraordinary concentrations of glycerine for antimycotic effect.

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 preventing the growth of spoilage microoganisms in the 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 known as "water activity". Water activity represented by the symbol Aw, is defined as the ratio of the partial vapor pressure of water in a solution to the vapor pressure of pure water, both measured at the same temperature. It is used in connection with describing the patent 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 literature 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 moisture added to the casing being prepared according to the invention, to controllably lower the water ativity, Aw, to a level, commensurate with the particular moisturization level of a given casing, at which mold growth will be inhibited for as long a shelf life as the casing may be expected to have.

In general, the invention comprehends a large size tubular fibrous reinforced cellulosic food casing which is premoisturized by adding carefully controlled amounts of moisturizing water to the extent that the casing can be stuffed without the necessity of any prestuffing soaking. The controllably added moisture may vary from as low as about 20% to as high as about 40% of the total weight of the casing. A preferred range of moisture 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, preferably by inclusion in the moisturizing water, and the solution 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, determine the salt concentration required to maintain the water activity, Aw, in the casing at a value low enough, preferably not more than about 0.75 to insure against 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 weight of cellulose in the casing, will protect against mold growth in casings with moisture contents of from about 20% to about 40% of total casing weight by maintaining the casing Aw at about 0.75. In addition, sodium chloride is a normal constituent of processed foods and is a readily accepted addition to casings.

Higher concentrations 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 22.0%; ammonium chloride from about 3.1% to about 33.2%; calcium chloride from about 4.1% to about 35.9%; and potassium chloride from about 2.6% to about 68.7% of the weight of cellulose in the casing to produce the same general over-range results.

Example I In order to 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 component 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 culture 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 concentration of about 1 to 5 million mold spores per milliliter of solution. Among the mold cultures included in the mixture were Aspergillus niger (ATCC #1004), Chaetonium globosum (ATCC #16021), Memnoniella echinata (ATCC #11973), Myrothecium verrucaria (ATCC #9095), Trichoderma viride (ATCC #26921), and Whetzelinia sclerotiorum (ATCC # 18657), all of which were purchased from 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 sixteen mold cultures that were isolated as naturally occurring airborne contaminants obtained from within casing manufacturing sites.

Test solutions of the agar medium and mold inocuium were prepared with sodium chloride and propylene glycol separately, and in cross-combined variations in concentrations of 0%, 2.5%, 5%, 7.5%, 10%, 12.5% and one of 15% propylene glycol only, by total weight of test solution.

The test solutions were stored in covered dishes for seven days at ambient temperature and visually inspected for mold growth.

Table 1, below illustrates the results of the test.

TABLE 1 Culture dish mold growth studies - effect of salt and propylene glycol NaCI Propylene Glycol Concentration (%) Concentration 0 5 7.5 10 12.5 15 (%) O + + + + + - 2.5 + + + + - - 5.0 + + + - - 7.5 + + - - - - 10.0 + - - - - 12.5 + - - - - Blank Negative Control = No Growth.

Key. + = Mold growth present - = Mold growth inhibited These test results show that sodium chloride, has discernible mold inhibiting properties when present in relatively small quantities with another antimycotic agent, in this instance, propylene glycol.

Example 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 of 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, Aw, 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 antimycotically protected by means of salt additives.

In preparation for the experimental work for this Example, a number of pieces of size 8 shirred tubular fibrous cellulosic sausage casings having a maximum stuffing diameter of 4.76 inches, of 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 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 water prior to stuffing. No propylene glycol was included in any of these sample casings of this Example.

TABLE 2 Mold Growth Observations on High Moisture Content Fibrous Cellulosic Sausage Casings Preserved With Chloride Salts Casing Glycerol Moisture Chloride Salt Calculated Visible Sample (% of (% of total Type Amount water mold cellu- casing (% of activity growtha lose) weight cellu- (Aw) lose) no salt salt added added A 29.0 42.7 none 0 0.91 0.91 + B 27.0 33.3 NaCI 4.4 0.90 0.86 C 30.8 32.3 NaCI 4.1 0.89 0.84 D 28.5 39.4 NaCI 7.9 0.90 0.83 E 29.7 38.4 NaCI 9.4 0.90 0.81 F 30.6 33.6 NaCI 8.4 0.89 0.80 G 30.6 31.7 NaCI 8.8 0.89 0.78 H 25.1 39.1 NaCI 18.1 0.91 0.77 28.8 32.8 NaCI 18.1 0.90 0.73 J 32.9 34.0 CaCI2 16.5 0.90 0.79 a.After 3 months at 35"C: + = visible mold growth - = no visible mold growth Casing samples used in the experiment of this Example were shirred and compressed to make 175 feet (53.34 meters) casing lengths into 24 inch (61 centimeter) stick lengths which were retained in elastic sheathing overwraps.

Mold inoculant for this experiment was prepared as follows.

Five separate suspensions of mold inoculant were used. Aspergillus niger, (ATCC, #1004) Aspergillus glaucus, Geotricum candidum, and a Penicillium mold species found in high moisture casings, were all used separately and then all added to an additional mixed suspension containing Chaetonium globosum (ATCC #16021). Memnoniella echinata (ATCC # 11973), Myrothecium verrucaria (ATCC #9095), Trichoderma viride (ATCC #26921), and Whetzelinia sclerotiorum (ATCC #18657). Also included in this fifth inoculant were mold spores of nine mold cultures which had been isolated from mold contamination found on various cellulose food casings, and mold spores of sixteen mold cultures isolated from ambient airborne contaminants obtained at casing manufacturing locations.

The suspensions contained one to five million colony forming units per milliliter of 1% sodium citrate and were prepared using conventional aseptic procedures.

The cultures identified by the "ATCC" designations were purchased from the American Type Culture Collection, Rockville, Maryland.

The casing samples were inoculated by brushing several milliliters of each of the above-described mold suspension in 1/2 inch (1.27 centimeter) strips of shirred surface along the length of each shirred stick. Each of the five mold 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 35"C.

The mold growth results are shown in Table 2, above. Results were recorded as positive (+) if visible mold growth appeared in any one of the five areas where the separate mold suspensions had been inoculated, and negative (-) if mold growth was not visible in any of the inoculated areas.

The results in Table 2 show that casing sample A, the only sample with no salt at all included as an antimycotic, was the only sample which had visible mold growth within three months. Casing samples B through I, all of which had sufficient sodium chloride, NaCI, added as antimycotic, did not show visible mold growth within three months. The incorporation of the sodium 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 values mold growth would occur, down to 0.73 to 0.86, values where no mold growth occurred within three months.

Casing sample J had calcium chloride incorporated as an antimycotic and 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 sausage casings can be preserved by the incorporation of relatively small amounts of chloride salts.

Example 111 This example involved experimental work performed to show that chloride salts other than sodium chloride can be used as antimycotics for high moisture large size fibrous cellulosic sausage casings.

Basic data calculations were made according to known methods to establish the relationship between salt content and water activity, Aw, and the water activity, Aw, also determined experimentally where necessary.

The relationships 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 invention, that a water activity, Aw, of 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, NH4CI, and CaCI2 had their water activity, Aw, values determined by measuring RH with a Sina moisture sensor, and the water activity values for the KCl and the NaCI solutions were included as reported by Sloan and Labuza, Food Product Development, December, 1975, page 68.

Drawing Figure 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 the water to salt ratio expressed in grams of water per 100 grams of anhydrous solid salt. Figure 1 of the drawing shows this plotted data.

Using drawing Figure 1, the known composition of fibrous sausage casing and the water activity, Aw, calculation method described by Ross, the amount of each chloride salt required to preserve high moisture fibrous casing for various moisture levels and 33% glycerine was calculated. The calculations were based upon the use of a single chloride salt in each case, and the assumption that a water activity, Aw, of 0.75 will be low enough to preserve the casing during ten months of storage at 35"C.

Table 3, below, summarizes the calculations of this Example.

TABLE 3 Casing Chloride Salt Content Required To Reduce Casing Water Activity, Aw, To A Casing Preservation Value of Aw = 0.75 Target Casing Chloride Salt (weight % of cellulose) casing Water required to reduce casing final water moisture Activity activity to Aw = 0.75 (% of total without casing weight salt NaCI MgCl2 NH4Cl CaCI2 KCI 20 0.79 2.0 2.9 3.1 4.1 2.6 25 0.83 5.4 6.7 8.0 9.7 8.3 30 0.87 10.4 11.3 16.7 18.5 21.0 40 0.90 22.6 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 total casing weight has been found to be the practical moisture 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 be 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. As 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 IV 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 U.S.

application Serial No. 686,248.

In preparing the salt protected casing sample, a reel length of size 4tubular fibrous cellulosic sausage casing having a maximum stuffing diameter of 3.26 inches (8.28 centimeters) was treated with an 8.8% sodium chloride, 2% glycerol, 89.2% water solution 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 material. A plastic sizing disc was inserted in one end of each shirred length and that end closed with a metal clip. The behaviour 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 the two sample casings A and B are summarized below in Table 4.

TABLE 4 Composition of Casing Samples Containing Sodium Chloride and Propylene Glycol as Antimycotic Agents Casing Composition Sodium Water Glycerol Propylene Chloride (% of (% of Glycol (% of Total Cellulose) (% of Casing Cellulose) Casing Cellulose) Sample Weight) A 4.9 25.5 39.3 0 B 0 24.0 37.9 7.2 The sample casings of this Example were next stuffed with bologna sausage emulsion on an automatic stuffing machine. Stuffing performance of the two samples was identical. The diameters of the sausage lengths stuffed using the salt A casing were identical to the diameters of the propylene g lycol B casing measured both before and after smokehouse processing of the products. The color and appearance of the A and B casing sausage samples was also identical.

This Example shows that a shirred fibrous sausage casing containing 5% sodium chloride by weight of casing cellulose and 25% 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.

Example V This example shows that chloride salt applied to the inner surface of a fibrous cellulosic sausage casing migrates through the wall 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 22 fibrous sausage casing having a moisture content of 6% of the total casing weight had its internal surface treated with 75 milliliters of a saturated sodium chloride solution by a slugging technique. The casing was opened and the 75 milliliter salt solution slug was allowed to contact all portions of the interior surface for a brief period of time after which the excess salt solution was discarded.

At intervals after slugging, the outside surface was tasted with the tongue and the taste sensation was recorded. At each time interval, a different portion of the casing surface was tasted. The results are shown in Table 5.

TABLE 5 Migration of Sodium Chloride From Interior Casing Surface To External Casing Surface Time (seconds after slugging the internal casing surface with Taste of the external saturated salt solution casing surface 5 Sweet only, no salt 20 Sweet only, no salt 30 More sweet than salt 45 More sweet than salt 55 More sweet than salt 80 More sweet than salt 100 More salt than sweet 120 More salt than sweet 150 Salt only, no sweet 180 Strong salt only, no sweet This example demonstrates the migration 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 longer be detected. At 180 seconds, the salt taste was even stronger. After 180 seconds the casing was split so that the internal surface, 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 taste.

Thus salt applied to the internal casing surface is readily detected at the external casing surface and could thus prevent mold growth at both casing surfaces.

Example Vl This example 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 cellulosic 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 casing. This Example shows that no undesirable 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 moisture addition.

In the preparation of this example, fibrous casings from Examples II and IV were selected for measurement of the burst pressure. The casings were inflated with air and the pressure recorded when the casings burst.

The results are shown in Table 6, below.

TABLE 6 Effect of Chloride Salts on Burst Pressure of High Moisture No-Soak Fibrous Cellulosic Sausage Casings Salt Amount Burst Casing (% of Pressure Sample Type Cellulose) (mm mercury) IIA None 0 530 IIE NaCI 9.4 534 IIH NaCI 18.1 515 liJ CaCI2 16.5 522 IVA NaCI 4.9 771 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 virtually identical observed 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 contrasts to the customary method of addition by uniform imbibition of the solution onto the casing prior to shirring, and thus provides an alternative mode of practicing the invention.

In the preparation of casings for this Example, six-inch shirred lengths of size 8 shirred tubular fibrous cellulosic sausage casings having a maximum stuffing diameter 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 moisture and chloride salt contents, the test solutions were added to the bores of the shirred casings. The addition was made as uniformly as possible thoughout 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 35 C, and observed for visible mold growth as described in Example II, above.

It was observed that the mold growth 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 sample A, which had no added salt antimycotic, had visible mold growth due to its high water activity of 0.89. Casing sample B, which also had no added salt, did not show mold growth due to its lower water activity of 0.84. Casing samples Cthrough G contained salt antimycotic and did not show mold growth due to their low water activities. The observed non-uniform addition of salt antimycotic solution by direction addition to the bore of shirred casing did not influence interpretation of the mold growth results in terms of casing water activity.Thus, non-uniform addition of chloride salt solution does not prevent the chloride salt from acting as an antimycotic for no-soak casing.

TABLE 7 Preservation of No-Soak Casing By Addition of Sodium Chloride Salt Solution to the Bore of Shirred Casing Visible Casing Variables Mold Sodium Growth Moisture Glycerol Chloride Calculated After 13 Casing (% of (% of Salt (% of Water Months Sample Total) Cellulose) Cellulose) Activity At 35"C A 34.0 29.5 0 0.89 + B 24.0 29.5 0 0.84 C 34.0 29.5 5.9 0.83 D 24.0 29.5 2.4 0.80 E 34.0 29.5 9.8 0.79 F 24.0 29.5 4.5 0.78 G 34.0 29.5 14.4 0.76 Example VIII This Example involved reexamination of the Example II casings, which were examined for mold growth after three (3) months storage at 35"C, at later periods of time, six (6) eight (8) and ten (10) months. Table 8, below, shows the listing of the identical casing samples of Table 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 additional time periods as well as reproduced for the original three (3) month period.

TABLE 8 Periodic Mold Growth Observations On High Moisture Fibrous Cellulosic Sausage Casings Preserved With Chloride Salts Calculated Water Activity (Aw) No salt Casing salt added Visible Mold Growth at Sample added 3 mos. 6 mos. 8 mos. 10 mos.

A 0.91 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 0.91 0.77 - - - 0.90 0.73 - - J 0.90 0.79 - - - a. At 35"C + = visible mold growth - = no visible mold growth 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 chloride salt-containing casings with water activity 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 chloride salt was added as an antimycotic. Chloride salt antimycotic added to Casing B reduced the Aw to 0.86 and delayed the appearance of visible mold growth until eight months of storage time. Chloride salt antimycotic added to Casing D reduced the Aw further to 0.83 and also caused a delay in the appearance of visible mold growth to 8 months storage. Casing C, with salt antimycotic added to give an Aw of 0.84, did not show visible mold growth at 10 months storage although Casing D with a lower Aw of 0.83 showed visible mold growth. This indicates that an Aw of 0.84 is sufficiently close to the minimum value permitting mold growth that visible mold growth may fail to appear.Casings E through I did not show visible mold growth even after 10 months storage because of the addition of sufficient chloride salt antimycotic to reduce the Aw to 0.81 or below.

Example IX This example demonstrates that a casing water activity not exceeding about 0.75 is preferred where long term storage is required under commercial conditions of fluctuating temperatures. This example involves further reexamination of the casings described in Example II and in Example VIII.

Mold growth visible to the unaided eye was found unexpectedly after 12 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 80"F (about 18 to 27"C). Constant temperature 350C 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). Conceivably, temperature fluctuations caused moisture vapor migration from warmer areas of the casing to the cooler areas, thus raising the water activity of one area of the casing sufficiently to permit mold growth. The mold growth results are shown in detail in Table 9.

TABLE 9 Mold Growth Observations On High Moisture Fibrous Sausage Casings Preserved with Chloride Salts Calculated Water Acitivity Chloride salt (Aw) Visible Mold Growth (b) Moisture Type Amount if no When Glycerol (% of (% of salt salt After After Casing (% of Total Cellu- added is 12 42 Sample Cellulose) Weight) lose) added Months Months A 29.0 42.7 None 0 0.91 0.91 (c) + B 27.0 33.3 NaCI 4.4 0.90 0.86 + + C 30.8 32.3 NaCI 4.1 0.89 0.84 - D 28.5 39.4 NaCI 7.9 0.90 0.83 + E 29.7 38.4 NaCI 9.4 0.90 0.81 + F 30.6 33.6 NaCI 8.4 0.89 0.80 + G 30.6 31.7 NaCI 8.8 0.89 0.78 - H 25.1 39.1 NaCI 18.1 0.91 0.77 - I 28.8 32.8 NaCI 18.1 0.90 0.73 + (b) Casing stored uninoculated at fluctuating room temperature (c) Observation not made The preferred mode of practicing the invention is to use about 2% to 10% sodium chloride concentration by weight of cellulose in the casing, in combination with a casing moisture content of about 20% to 25% of the total casing weight, adjusting these parameters to attain a finel calculated casing water Activity, Aw, of about 0.75 or lower.

The foregoing description and examples and the experimental data therein show that chloride salts are effective antimycotic agents in large size fibrous cellulosic 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 as, for instance, propylene glycol, not only provides an economic 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 laws in some countries closely control the use of polyol softeners and in some European countries, the use of the softener 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 the problems overcome, the advantages provided, and the novel and advantageous features of this invention. The foregoing description of the invention is intended to be illustrative only and should not be construed in any limiting sense.

Claims (22)

1. A large size tubular cellulosic food casing controllably premoisturized to an extent that it can be stuffed without the addition of further moisture prior to stuffing, having a content of a chloride salt selected from the group consisting of sodium chloride, magnesium chloride, ammonium chloride, calcium chloride, and potassium chloride, in a concentration of weight percent of cellulose in the casing to maintain the water activity in the casing at not more than 0.81.

2. A casing as claimed in claim 1, wherein the chloride salt is sodium chloride in concentration of from about 2% to about 22.6% of weight of cellulose in the casing.

3. A casing as claimed in claim 1, wherein the chloride salt is magnesium chloride in concentration of from about 2.9% to about 22.0% of weight of cellulose in the casing.

4. A casing as claimed in claim 1, wherein the chloride salt is ammonium chloride in concentration of from about 3.1% to about 33.0% of weight of cellulose in the casing.

5. A casing as claimed in claim 1, wherein the chloride salt is calcium chloride in concentration of from about 4.1% to about 35.9% of cellulose in the casing.

6. A casing as claimed in claim 1, wherein the chloride salt is potassium chloride in concentration of from about 2.6% to about 68.7% of cellulose in the casing.

7. A casing as claimed in any one of the preceding claims, wherein the moisture content is not greater than 40% of the total casing weight.

8. A casing as claimed in any one of the preceding claims, wherein the water activity in the casing is maintained at not more than 0.75.

9. A casing as claimed in any orie of the preceding claims, wherein a fibrous support web is embedded in the walls thereof.

10. A casing as claimed in claim 1, substantially as hereinbefore described in any one of the foregoing examples.

11. A method of making a large size tubular cellulose food casing for stuffing with food product without the addition of further moisture prior to stuffing, which comprises adding moisture if necessary to achieve the desired moisture content and adding a chloride salt selected from the group consisting of sodium chloride, magnesium chloride, ammonium chloride, calcium chloride and potassium chloride, in a concentration of weight percent of cellulose in the casing, to maintain the water activity in the casing at not more than 0.81.

12. A method of making a large size tubular cellulose food casing for stuffing with food product without the further addition of pre-stuffing moisture which method comprises the improvement of the steps of: adding moisture to give from about 20% to about 40% by total casing weight of moisture in the casing, and adding from the group consisting of

2.0% to 22.6% NaCI

2.9% to 22.0% MgC12 3.1% to 33.2% NH4CI 4.1% to 35.9% CaCI2

2.6% to 68.7% KCI a chloride salt in a concentration of weight percent of cellulose in the casing, according to the moisture content in the casing, to maintain the water activity in the casing at not more than 0.81.

13. A method of making a large size tubular cellulose food casing as claimed in claim 12, wherein the water activity in the casing is maintained at not more than 0.75.

14. A method of making a large size tubular cellulose food casing as claimed in claim 12 or 13, wherein a fibrous support web is embedded in the walls of the casing.

15. A method as claimed in claim 12, 13 or 14, wherein the moisture is added to the casing to provide a total moisture content of from about 20% to about 25% of the total casing weight, and sodium chloride added is from about 2% to 10% by weight of cellulose in the casing.

16. A method of making a large size tubular casing substantially as hereinbefore described in any one of the foregoing examples.

17. A method of making a food product encased in a large size tubular cellulose casing comprising selecting such a casing containing from about 20% to about 40% moisture by total casing weight, and a chloride salt selected from the group consisting of sodium chloride, magnesium chloride, ammonium chloride, calcium chloride, and potassium chloride in a concentration of weight percent of cellulose in the casing to maintain casing water activity at not more than 0.81, and stuffing said casing with food product without the further addition of moisture to the casing by soaking prior to stuffing.

18. A method of making a food product encased in a large size tubular cellulose casing as claimed in claim 17, wherein the water activity in the casing is maintained at not more than 0.75.

19. A method of making a food product encased in a large size tubular cellulose casing as claimed in claim 17 or 18, wherein a fibrous support web is embedded in the walls of the casing.

20. A method of making a food product encased in a large size tubular cellulose casing which comprises stuffing a casing as claimed in any one of claims 1 to 10 with food product without the further addition of moisture to the casing by soaking prior to stuffing.

21. A food product encased in a large size tubular cellulose casing, wherein said casing is as claimed in any one of claims 1 to 10.

22. A food product encased in a large size tubular cellulose casing whenever produced by a method as claimed in any one of Claims 17 to 20.