GB819116A - Artificial tubing - Google Patents

Abstract

A casing, particularly for sausage meat, comprises at least 50 per cent of a water-dispersible or water-soluble dextran having a molecular weight between 20,000 and that of native, unhydrolysed dextran. The dextran is preferably obtained from sucrose by biosynthesis, using strains of the micro-organism Leuconostoc. The casing may be formed from a dextran derivative, e.g. a nitrate, which may be prepared by reacting dextran in solid particulate condition or dissolved or dispersed in water with concentrated or fuming nitric acid or with a mixture of nitric acid and nitrogen peroxide. Other suitable dextran derivatives are the formate, acetate, butyrate, xanthate, ether xanthate, thiourethane xantho fatty acid, ether, or glycollic acid ether or salt. The dextran derivative is subsequently treated to reconstitute the dextran. Up to 50 per cent of a compatible film-forming material may be incorporated in the solution of dextran or dextran derivative from which the casing is made, e.g. cellulose nitrate, water-soluble hydrolysed polyvinyl acetate or water-soluble carboxymethyl cellulose. The casing may be produced by extrusion of a solution comprising dextran or a dextran derivative through an annular nozzle into a coagulating medium, from which the casing is withdrawn and, if necessary, treated to reconstitute the dextran. Plasticizers which may be incorporated in the extrusion solution include glycerol, ethylene glycol, propylene glycol and polyethylene glycol. Dextran nitrate solutions may be formed into tubing by dry or wet extrusion methods. Thus, when the dextran nitrate is soluble in water, viscous solutions may be extruded either into a hot inert gaseous atmosphere to evaporate the water or into diethyl ether, and when the dextran nitrate is insoluble in water it may be dissolved in isopropanol or a solvent mixture, e.g. ethyl alcohol and diethyl ether, and spun into water. Reconstitution of dextran in tubing comprising dextran esters may be effected by treatment with an alcoholic or aqueous solution of sodium hydrosulphide, with alcoholic sodium hydroxide or with a suspension of a hypophosphite or a dithionate, e.g. sodium hypophosphite or sodium dithionate, in alcohol. The tubing may be stretched laterally and longitudinally either in the coagulating bath or subsequently. Lateral stretching may be effected by maintaining a pressure differential, e.g. by the use of a vacuum outside the tubing and/or fluid pressure within. Examples are given.