Cellulose casing for food products

Details Cellulose casing for food products Cellulose casing for food products

2002-06-07

2004-06-29

Pyon, Harold (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Flexible food casing

C428S035600, C428S035500, C138S118100

Reexamination Certificate

active

06756093

ABSTRACT:

This application is the national phase under 35 U.S.C. § 371 of PCT International Application No. PCT/FI00/00922 which has an International filing date of Oct. 25, 2000.
BACKGROUND OF INVENTION
The present invention relates to cellulose food casings and more particularly to transparent pigmented tubular cellulose food casings and to a method for the manufacture thereof.
Cellulose casings are widely used in food industry, specially in meat industry in the production of stuffed food products, such as sausages and the like, and they often are coated with various substances or they have substances incorporated into the casing.
Cellulose casings are supplied in great lengths that are folded into highly compressed pleats forming rigid tubes formed of regenerated cellulose and containing plasticizers such as water and/or a polyol such as glycerine. The cellulose used for the manufacture of casings is most commonly produced by the so-called “viscose process” wherein viscose, a soluble cellulose derivative, is extruded as a tubular film through an annular die into coagulating and regenerating baths to produce a tube of regenerated cellulose. The tube is subsequently washed, plasticized and dried. The casing may be non-reinforced or reinforced with fibers such as paper.
In the “viscose process” natural cellulose is treated with a caustic solution to activate the cellulose to permit derivatization and to extract certain alkali soluble fractions from the natural cellulose. The alkali cellulose obtained is shredded, aged and treated with carbon disulphide to form sodium cellulose xanthate, which is then dissolved in a weak caustic solution. The viscose solution is ripened, filtered, deaerated and extruded.
Food casings made of derivatized cellulose usually contain additives such as colorants incorporated in or onto the casing. Liquid smokes which impart a smoky flavour and a reddish colour to the food product may also be incorporated in or coated on the casings.
From U.S. Pat. No. 4,336,828 a fiber-reinforced metallic luster pigmented tubular casing and a process for the manufacture of it are known. In the manufacture of the fiber-reinforced tubular casing, a pearlescent flake pigment which preferably comprises primarily titanium dioxide-mica silver or gold or copper pigment, is mixed with an alkaline solution of commercial-grade cellulose xanthogenate, and a long fiber paper reinforced substrate is contacted and impregnated with the obtained mixture and then the impregnated mixture is hardened on the said substrate. From US-patent H1,592 is known a cellulosic food casing made from non-derivatized cellulose and N-methylmorpholine-N-oxide, wherein colouring agents such as reds, blues and yellows may be introduced into the cellulose solution prior to extrusion from the die. In patent DE 3543633 are disclosed sausage casings for raw-type sausages which are manufactured from fiber-reinforced regenerated cellulose tubes and coated on the inner surface with a water-insoluble cationic resin. The outer surface of the cellulose tubes contains 8-20% pigment and only little pigment is present at the inner cellulose surface.
Variety of colours are used in casings and usually pigments are incorporated into the cellulose prior to extrusion. The commonly used red colour or different shades of red, such as reddish-brown, “colour of a well-smoked” and specially mahogany colour in casings is usually achieved by using vat-dyeing technology based for example on the Indanthren group of dyes (these dyes are manufactured by Dyestar Company). The colouring of the casings is accomplished by injecting the dye or pigment into viscose, then mixing to obtain a good dispersion of the dye and viscose, followed by impregnating the fibrous casing paper support of substrate, and then coagulating the mixture on or in the paper followed by regeneration. Once the cellulose is regenerated using baths containing diluted sulphuric acid together with ammonium and sodium sulphate salts, the casing as a flattened tube is passed into a reducing alkaline sodium hydrosulphite bath, which renders the vat-dye soluble to facilitate its movement between the swollen cellulose molecules or chains of cellulose. Thereafter the tubing is passed to an alkaline peroxide oxidizing bath which has the effect of re-crystallizing the Indanthren dye captivated between adjacent cellulose chains and finally the whole process being completed by a sulphuric acid neutralization bath closing up the cellulose chains, which are swollen under the effect of alkali, to discourage migration. Thus, a highly transparent or clear casing with a reddish or mahogany colour, giving the product a desired smoked appearance, is obtained.
Also other pigments are used to provide colours or shades other than mahogany such as reds, browns, whites, metallic luster pigments, blacks, blues, greens, yellows, oranges, many of which are used either alone or in a mixture. However, compared to the shades provided with Indanthren type of dyes and other vat-dyes the casings provided by these pigments tend to be flat and opaque.
The widely used vat-dyeing technology has some major disadvantages. In the processing there lies a need for extra processing steps i.e. reducing by hydrosulphite bath, oxidizing by peroxide bath and neutralizing by acid baths. The additional baths contain up to 25 g/l of sodium hydroxide and between 5 and 35 g/l of sodium dithionite, used at a temperature of 25 to 55° C., which has the effect of converting the Indanthren dyes to their soluble reduced forms, followed either by a number of wash baths, the last of which can comprise an acid neutralisation stage, using approx. 10 to 60 g/l of sulphuric acid and a temperature of 15 to 65° C., to convert them back to their crystalline oxidised forms, or a number of wash baths containing also 2 to 20 g/l of dilute sodium peroxide solution at 15 to 45° C. to assist the conversion back to the oxidised forms, prior to neutralisation as before. The latter baths can contain strong corrosive chemicals, which can lead to a weakening of the cellulose structure of the casing. The use of these baths, while being costly to be kept refreshened with chemicals and hot water and mechanically maintained, they take up additional space and once so treated, the casing product is mechanically weaker than its non-vat-dyed counter-part because of the absence of such chemical interactions. Additionally, because several baths with lots of chemicals are used, environmentally undersired waste chemical solutions are formed.
Chemical reduction has from time-to-time been a problem with the Indanthren dyes if they have not been properly fixed in the casing i.e. between adjacent chains of cellulose within the wall of the casing. The phenomenon of reduction may occur in vat-dyed casings which contain meat emulsion, such as summer sausages, also known as balkan sausage. The sausage is often vacuum-packed for extended shelf-life reasons even up to 12 months and micro-organisms, such as bacteria, which are always present to a larger or lesser extent in such products, begin to act chemically and affect the oxidation state of the dye. In many cases this change in oxidation state is accompanied by a change in colour. Oxidised colour, reddish brown changes to reduced form, dark green, which may give rise to complaints of the product being streaked black and therefore contaminated.
Based on the above it can be seen that there is a need for an improved method for the manufacture of a pigmented cellulose casing, particularly of a mahogany coloured cellulose casings and for a pigmented cellulose casing, particularly a mahogany coloured cellulose casing.
SUMMARY OF INVENTION
An object of the invention is to provide a method for the manufacture of a pigmented cellulose casing, particularly mahogany coloured cellulose casings and a pigmented cellulose casing, particularly a mahogany coloured cellulose casing obtained thereby, which are not subject to discolouration by virtue of microorganism activity in a vacuum pack.
A further object of the present invention is t

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