Manufacture of Gelatin Marek Matusik

Gelatin is a translucent brittle solid substance, colorless or slightly yellow, nearly tasteless and odorless, extracted from the collagen inside animals' connective tissue. It has been commonly used in food, pharmaceutical, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar way are called gelatinous. Gelatin is an irreversibly hydrolyzed form of collagen. Gelatin is also known as E number E441. Gelatin is a protein produced by partial hydrolysis of collagen extracted from connective tissues of animals such as the domesticated bovines, porcines and equines. The natural molecular bonds between individual collagen strands are broken down into a form that rearranges more easily. Gelatin melts when heated and solidifies when cooled again. Together with water it forms a semi-solid colloidal gel. birefringence.

Application Common examples of foods that contain gelatin are: - jellies - desserts - candies - trifles - aspic - marshmallows - gummy bears

Gelatin may be used as a stabilizer, thickener, or texturizer in foods such as: - Ice cream - Jam - Yoghurt - Margarine Gelatin is used for the clarification of juices, such as apple juice, and of vinegar. Isinglass, from the swim bladders of fish, is still in use as a fining agent for wine and beer.

Technical uses - Gelatin typically constitutes the shells of pharmaceutical capsules in order to make them easier to swallow. Hypromellose is the vegetarian counterpart to gelatin, but is more expensive to produce. - Animal glues such as hide glue are essentially unrefined gelatin - It is used to hold silver halide crystals in an emulsion in virtually all photographic films and photographic papers. Despite some efforts, no suitable substitutes with the stability and low cost of gelatin have been found. - Gelatin is closely related to bone glue and is used as a binder in match heads and sandpaper.

Selected Raw Materials for the Manufacture of Gelatin Pig and cattle skin In the skin processing industry, the skin of slaughtered animals is first thoroughly washed. The layer of connective tissue on the meat side of the skin is then removed by machine and the skin horizontally split. The intermediate layer, so called hide split, consists mainly of collagen and is thus excellently suited to the manufacture of gelatin. The hide split is preserved using salt or calcium hydroxide, which keeps it fresh until it is used in the gelatin manufacturing process.

Bone chips. In meat processing, fresh bone is a by-product that is used in the production of gelatin. However, before it is used, it is subjected to a stringent pretreatment process. As a first step, bone is reduced to pieces of between 5—10 mm. These are then degreased with hot water, dried and separated into various particle sizes. Potential bone adherent tissues are removed in the degreasing process. The bone chip material is then stored in silos until required for production purposes. Demineralization of bone chips. Treatment of this intermediate product with dilute hydrochloric acid at low temperature over several days using the reverse flow process removes any phosphate contained in the bone. This process is known as "maceration" and the demineralized bone chips as "ossein". The surplus acid is then removed from the ossein by thorough washing.

Raw Material Pretreatment. Acid processing. For gelatin of type A (acid), pigskin is normally used as starting material. Pigs, in contrast to cattle, are slaughtered at a relatively young age. Since the skin of such young animals is not as highly cross- linked, a more gentle process than the tedious alkaline process can be used; in this case, acid is used. All that is required is a one-day treatment with dilute acid, and the collagen of the pigskin is rendered soluble in warm water, a precondition for the subsequent extraction process. Any superfluous acid is partly neutralized and the remaining salts washed out with several washings of water. Ossein can also be processed to gelatin using this method with appropriate acid concentrations and treatment times. However, gelatin produced in this way is relatively unimportant. Alkaline processing. Gelatin of type B (basic) is produced from ossein pretreated with alkali or from washed and cut hide splits. In this process, the raw materials are treated for a period of up to three months with calcium hydroxide, which is renewed several times during the period. In this process, the collagen bonds are partially separated and any noncollagenous proteins and related substances removed. As an alternative process, the raw material can be treated over a period of one to two weeks with dilute sodium hydroxide solution instead of calcium hydroxide. Subsequent to this process, the treated raw material is washed, neutralized by adding acid, and washed again to remove any residual salts.

Process flowchart

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