Chemistry: natural resins or derivatives; peptides or proteins; – Proteins – i.e. – more than 100 amino acid residues – Scleroproteins – e.g. – fibroin – elastin – silk – etc.
Patent
1995-09-19
1999-03-02
Smith, Lynette F.
Chemistry: natural resins or derivatives; peptides or proteins;
Proteins, i.e., more than 100 amino acid residues
Scleroproteins, e.g., fibroin, elastin, silk, etc.
530354, 530350, C07K 100, C07K 1400, C07K 1700, A61K 3817
Patent
active
058772871
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for producing gelatin from a collagen-containing raw material.
Gelatin is a natural product that is used primarily in the food industry, but also in the pharmaceutical, the photographic, the textile and the paper industry.
Gelatin is a protein obtained from collagen that occurs in the skin, connective tissue, bones and other parts of animals, mammals as well as fish. In the bone phase, the collagen is present in the form of a fibrous matrix surrounded by inorganic material. When looking at suitably-colored bone phase under the microscope, one sees that the bone phase is crisscrossed by densely-packed bundles of collagen fibres. Under an electron microscope, these fibres are seen to consist of fibrils that are about 400-1200 .ANG. in diameter. The fibrils have a cross-striped structure similar to that of connective tissue. On average, collagen makes up almost a third of the bone phase, based on dry weight. The inorganic phase consists of small, densely-packed crystals (50.times.600 .ANG.) having an X-ray diffraction pattern similar to that of hydroxyapatite, 3.Ca.sub.3 (PO.sub.4).sub.2.Ca(OH).sub.2.
The collagen fibrils are composed of rod-shaped collagen molecules (tropocollagen) having a length of 300 nm and a thickness of 1.5 nm. The tropocollagen is composed of three polypeptide chains, so-called .alpha.-chains, forming a triple helix. In the fibrils, the tropocollagen is cross-linked by covalent bonds primarily located at the molecule ends, the so-called telopeptides. Native tropocollagen is highly resistant to alkaline, acid and enzymatic hydrolysis, owing to its densely-packed helix structure. However, the telopeptides do not have such a high resistance, since they are not integrated in the helix structure, but may be regarded as randomised or globular regions.
When the collagen molecule is heat-denatured, the triple helix is untwined, and free polypeptide chains are formed, i.e. gelatin is obtained. When the collagen molecules are present in such tissue as bone tissue, the situation is more complex. In order that the tropocollagen molecules should be dissolved and heat-denatured to gelatin, the covalent cross-links between the molecules have to be broken up. This can be brought about e.g. by high-temperature heating (autoclaving). However, such heating not only breaks up the cross-links, but also causes random hydrolysis of the bonds in the tropocollagen, resulting in gelatin of poor quality. In the method most commonly used, the telopeptides and, hence, the cross-links are hydrolysed at a low temperature (15.degree.-25.degree. C.), leaving the triple helix intact and rendering the tropocollagen extractible.
In conventional techniques for producing gelatin from bone, the whole bones or bones divided into pieces are first demineralized completely with acid at a low temperature and for several days, so that the collagen matrix is exposed and ossein is obtained. Demineralization, which is performed in a separate step, implies treatment at a pH<2, in which large amounts of acid are consumed. Separate and complete demineralization is an extremely important part of today's gelatin production on the basis of bone raw material. The purpose of such demineralization is to dissolve the calcium salts in the bone, thereby to expose the collagen matrix. Calcium is present in the form of hydroxyapatite, which is dissolved by treatment with diluted hydrochloric acid. After demineralization, the ossein is "conditioned" by means of alkali, such as lime or lime milk, for 1-6 months at a low temperature. In this treatment, the intramolecular bonds are broken up, the solution is neutralised and the collagen is extracted at an elevated temperature (50.degree.-95.degree. C.). The collagen is denatured, and gelatin is obtained.
Present-day methods for producing gelatin distinguish between whether the raw material employed is bone or hide (split, rind) and other connective-tissue material.
Containing no minerals, hide and connective tissue are not subjected to any demineralization, but
REFERENCES:
patent: 4389423 (1983-06-01), Madsen
Ward et al., Chapter 9, Raw Materials, The Science and Technology of Gelatin, pp. 295-364 : 1977.
Application of Enzymes in Gelatin Processing, Novo Enzymes : 1986.
Larsson Mats
Lilja Mats
Ellco Food AB
Nelson Brett
Smith Lynette F.
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