Method of preparing an edible tubular collagen casing

1,122,504. Tubular films. TEE-PAK Inc 22 March, 1966 [26 March, 1965], No. 12442/66. Heading B5B. An edible translucent sausage casing comprising cohered limed hide collagen fibrils is made by treating a fresh or salt-cured animal hide with a lime-containing solution for a time, in the range 1.5 to 24 hours, sufficient toatleastpartially dehair the hide without degrading the collagen; removing the epidermal layer and remaining hair, neutralizing the lime in the hide by treatment at a pH of 2.5 to 6.5 with a non-toxic acid capable of forming a calcium salt, sufficiently soluble to be washable from the hide, and washing to remove by-product salts, grinding the hide at a temperature less than 20‹ C. to produce a slurry of finely-divided collagen in water, treating the slurry with acid at a pH of 2.5 to 3.7 for a time sufficient to swell the collagen and burst the fibre bundles to form fibrils. extruding the slurry through an annular die to form a collagen tube, immersing the tube in a coagulating bath, tanning the collagen tube, and washing, plasticizing, and drying the tube to produce a translucent non- fibrous edible product. Suitably the lining treatment is effected for 3 to 12 hours. Preferably, the epidermal layer and remaining hair are removed mechanically, and the neutralized hide is defieshed and cut into pieces prior to grinding. Suitably the slurry contains 2-6% collagen, and especially 3À5-5%. The lime solution is preferably a solution containing excess solid lime, sodium sulphhydrate, and dimethylamine sulphate. The acid used for neutralizing the lime and for swelling the collagen is suitably a weak organic acid, especially acetic acid, lactic acid, citric acid, or propionic acid. Acids which may be used to neutralize the limed hide may be selected from malic acid, maleic acid, butyric acid, isobutyric acid, fumaric acid, succinic acid, valeric acid, glutamic acid, levulinic acid, lactic acid, citric acid, acetic acid, propionic acid, caprylic acid, gluconic acid, benzoic acid, malonic acid, ascorbic acid, glycerophos phoric acid, hydrochloric acid, and phosphoric acid. The coagulating bath preferably contains a salt selected from alkali metal sulphates and ammonium sulphate, and the following baths are used in examples: (1) 42% ammonium sulphate; (2) 40% ammonium sulphate; (3) 42% sodium sulphate; (4) 42% sodium sulphate; (5) 30% ammonium sulphate; (6) 30% ammonium sulphate; (7) 42% ammonium sulphate; (8) 42% ammonium sulphate. The tanning bath s