Patent GB-1122505-A (GB)
Title: Dialdehyde tanned edible collagen casing
Inventor: ROSE HENRY JACOB
IPC: B29C48/10
Filed: 1966-04-18
Abstract: 1,122,505. Tubular collagen films. TEEPAK Inc. 18 April, 1966 [28 June, 1965], No. 16876/66. Heading B5B. A process of tanning an extruded edible casing comprising collagen fibrils comprises contacting said casing with a solution of an edible non-toxic dialdehyde at a pH of 4.0 to 7.0 and washing and drying the casing. The dialdehyde solution may contain a buffer salt. Preferably, the casing is contacted with a solution of glutaraldehyde or condensed smoke containing non-toxic dialdehydes in solution, e.g. the commercially available Griffith SF 12 " liquid smoke " (actually a condensed smoke) adjusted to a suitable pH, or alternatively, may be a solution of so-called " liquid smoke" made by passing smoke from sawdust or wood shavings burnt under controlled combustion conditions and passed through water, having a suitable pH. Suitably, the solution contains glutaraldehyde at a pH of 4 to 6, the solution desirably having a glutaraldehyde concentration of 1 to 50% by weight. In a preferred method an edible tubular collagen casing is made by defleshing an animal hide and removing the epidermal layer and hair therefrom, cutting the hide into pieces, grinding the hide pieces 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 to swell the collagen, (the ground collagen is suitably swollen by a solution of lactic acid or citric acid), extruding the slurry through an annular die to form a collagen tube, immersing the tube in a coagulating bath containing 0 to 5% by weight of a non-toxic dialdehyde, tanning the collagen tube by contacting the same with a buffered solution of an edible non-toxic dialdehyde at a pH of 4À0 to 7.0, and washing, plasticizing and drying the tube to produce a translucent, non-fibrous, edible product. In another preferred method, a fresh or salt-cured animal hide is treated with a lime-containing solution (suitably a slurry of solid lime, sodium sulfhydrate (NaSH), and dimethylamine sulphate), for a time sufficient to at least partially de-hair the hide, removing the epidermal layer and remaining hair, neutralizing the lime in the hide by treatment with a non-toxic acid capable of forming a soluble calcium salt, at a pH of 2.5 to 6.5, 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 to swell the collagen, (weak acids e.g. oitric acid or lactic acid are suitable), extruding the slurry through an annular die to form a collagen tube, immersing the tube in a coagulating bath, tanning the collagen tube by contacting the same with a solution of glutaraldehyde or condensed smoke containing non-toxic dialdehydes in solution at a pH of 4.0 to 7.0, and washing, plasticizing, and drying the tube to produce a translucent non-fibrous edible product. Collagen casings so made are dried and shirred in conventional manner. Suitably, the coagulating bath consists of a concentrated solution of sodium sulphate or ammonium sulphate. In examples (1) a coagulating bath consisting of 42% ammonium sulphate and 0À5% by weight glutaraldehyde is used; (2) a coagulating bath consisting of 35% ammonium sulphate in water is used; (3) 30% ammonium sulphate; (4) 42% ammonium sulphate; (5) 42% ammonium sulphate; (6) 42% ammonium sulphate; (7) 42% ammonium sulphate and 3 to 10% by weight glutaraldehyde; plasticizing baths specified include 5% glycerol in water. Tanning baths employed include in examples: (1) 5% aqueous glutaraldehyde solution buffered to pH 5.3 with sodium hexametaphosphate; (2) 25% by weight glutaraldehyde solution buffered to pH 5.7 with sodium formate; (3) a concentrated solution of condensed smoke adjusted to a pH of 4.5 (Griffith SF 12 liquid smoke); (4) a solution of 10% by weight glutaraldehyde and 5% by weight " liquid smoke" having a pH of 5.3; (5) a solution of 10% by weight glutaraldehyde buffered to pH 5.9 with sodium formate; (6) a solution of condensed smoke made by passing smoke from sawdust of wood shavings burnt under controlled combustion conditions and passed through water, having a pH of 5.2; (7) a solution of 10% by weight glutaraldehyde and 5% " liquid smoke ", buffered to pH 4.9. The only plasticizing bath disclosed is 5% glycerol in water. In apparatus as shown, the collagen slurry is introduced through inlet conduit 1 into die 2 having an annular die outlet 3 through which casing 4 is extruded. Die 2 has an inner tube 5 extending upwardly within the extruded casing to remove coagulating bath from therewithin. Die 2 is located at the bottom of container 6 which contains coagulating bath 7, bath 7 being circulated through conduit 8 from tube 5 for removal of the coagulating bath from inside the extruded casing. Casing 4, coagulated in bath 7, passes over a series of rollers and is directed through the tanning, washing, and plastiaizing baths shown, to the drying, reeling, and shirring stages.