How is gelatine made?
gelatin is a tasteless animal protein (polypeptide) that contains all essential amino acids apart from tryptophan. To obtain it, the initially insoluble connective tissue from (mainly) the skin and bones of pigs and cattle, but also poultry and fish, is subjected to a digestion process (hydrolysis) that breaks down the peptide bonds so that the collagen that has been made water-soluble can be extracted. The digestion can be done by boiling (making a boullion in the kitchen) or by treatment with acids and bases and subsequent extraction (industrial production). Gelatin can contain 1-2% minerals and up to 15% water.
Gelatine swells in water and then dissolves when heated (from approx. 50 ° C). It is the only hydrocolloid in which the gelled solution (when cooled) becomes liquid again when heated. This temperature-dependent gel / sol transition is reversible and is, for example, also responsible for the fact that gummy bears melt in the mouth (and do not stick like starch products, for example). Gelatine is sensitive to temperature. If it is heated over 80 ° C for a long time, it degrades, i.e. it loses more and more of its gelling power (measured in Bloom).
Like all other proteins, gelatin has amphoteric properties. Therefore there is a pH value at which the (positive) electrical charge of the amino groups corresponds to that of the (negative) charge of the carboxyl groups. This isoelectric point of the gelatine depends on the production method (acidic digestion: pH 5, alkaline digestion: pH 7-9). Gelatin is most insoluble at the isoelectric point, which can be used as a method of determination (greatest cloudiness of the gel).
Gelatine is used to gel food (e.g. gummy bears, jelly, brawn). They are also used for the production of film layers (especially photo paper) and for the production of medicinal (soft and hard) capsules, to name the most important areas of application.
Gelatine is not suitable for a vegetarian diet because it is made from connective tissue (which is only found in animals and humans). Vegetarian (but technologically limited) alternatives to gelatine are agar-agar as well as pectin and carrageenan.
Used in Europe Edible gelatine is made from approx. 70% pork rinds (approx. 5 kg pork rinds make 1 kg gelatine). 28% percent of the raw material comes from beef. This is primarily (18%) from beef fissure (middle layer of the skin), and 10% from beef and pork bones. The bones are crushed, defatted and freed of calcium carbonate, calcium phosphate and calcium fluoride during maceration. The demineralized substance is called Ossein. Poultry and fish skin are used to make the remaining portion (2%) of the gelatine.
While basic bonds in the ossein and cattle split are broken down with milk of lime over a longer period of time (3-6 months) and with the formation of ammonia, the acidic digestion of the pork skin with sulfuric or hydrochloric acid takes place within a day. After washing out, what remains is the pure collagen, which is now soluble in warm to hot water as a result of the treatment, from which gelatin with ever lower gelling power is extracted in several (up to 5) batches (boullions) with increasing temperature (and associated with it). The gelatin solutions obtained in this way are thickened and cooled, whereby they gel and the gelatinized mass can be extruded in noodle form onto a drying belt. The belt then runs through a drying tunnel, at the end of which the gelatine is dried to a water content of 10-15%. For the production of sheet gelatine, it is not extruded in noodle form, but a gelatine film is produced, for which a wide-meshed net serves as a drying band.
Because of the BSE crisis, the EU Commission set strict guidelines for the production of gelatine in 1999.
Fish gelatin is made from the collagen contained in fish skins, among others. in order to comply with Jewish and Islamic dietary laws (see Kosher and Halal). Fish is one of the most allergenic foods and there can be pronounced allergic reactions to fish. However, there have been no reports of clinical reactions to gelatin in commercially available foods. However, since there is a lack of sufficient data from provocation studies with people who have a fish allergy and who have specific IgE to fish gelatine or who react positively to a prick test with fish collagen or fish gelatine, the data presented by the Swiss fragrance and aroma manufacturer Givaudan were used in 2004 on the occasion of an application for approval of EFSA rated fish gelatine as insufficient for encapsulating flavorings. On the other hand, the opinion was expressed that "it is not very likely that fish gelatine will cause a severe allergic reaction in the majority of people with fish allergy under the conditions of use specified by the applicant."
Gelatine is sometimes used in semi-fat products and light products such as semi-fat margarine, semi-fat butter and low-fat cheeses, as well as in confectionery such as gummy bears, wine gums, soft caramels, marshmallows, foam wafers, liquorice or chocolate kisses. It can also be used in baked goods, dairy products (such as quark, kefir and yoghurt) and desserts (e.g. jelly, jelly pudding), in meat, fish and sausage products such as jellied meat and aspic, mints and Christmas confectionary, but also as a fining agent in drinks such as wine, cider and fruit juices and in some countries even in beer.
Gelatine is also contained in the usual films and photo papers, in most photographic high-quality printing processes it is the carrier of the pigment or chemical layer. In make-up making in film and theater or in rescue exercises, colored gelatine is used for realistic wounds. The organs, as you see them in hospital series, for example, are also often made of gelatine. In addition, in the sport of paintball, it is used as a cover for biodegradable ammunition. Ballistic gelatine is used to determine shot channels or the penetration depth of a projectile.
Gelatine is used in the pharmaceutical industry for the production or in the pharmacy for the further processing of hard and soft capsules and in suitable cases to increase the viscosity of solutions as gelatine A (acidic digestion) or gelatine B (alkaline digestion) (see thickeners). Although there are more types of gelatine, practically only these two are used there. In medicine, gelatine is used, among other things, to coat implants such as vascular prostheses.
In addition to gelatine, by-products are created during gelatine production, which are used further: meat bone meal (for example as animal feed or fertilizer), bone fat (for example for soap production) and calcium carbonate (for example for toothpaste production).
Vaccines containing gelatin
Bovine gelatine in the form of polygelin as a stabilizer is or was contained in several vaccines, for example those against TBE, Japanese encephalitis, rabies, varicella and the MMR vaccine. Although allergic reactions to vaccines with a frequency of approx. 1 reaction to 500,000 vaccine doses are rare, allergy to gelatine (in combination with thiomersal) plays an important role as an allergic reaction of the immediate type (up to anaphylaxis) and applies to approx. responsible for half of all related complications, so these are now increasingly being removed from vaccines.
- ↑ Gelatine Market Data (Gelatine Manufacturer of Europe)
- ↑ Opinion of the Scientific Panel on Dietetic Products, Nutrition and Allergies at the request of the Commission regarding a communication by Givaudan Schweiz AG regarding fish gelatine for use as a flavor carrier in accordance with Article 6 (11) of Directive 2000/13 / EC. (Question EFSA-Q-2004-126)
- Wilfried Babel: Gelatin - a versatile biopolymer. In: Chemistry in our time, 30 (1996), pp. 86-95, ISSN 0009-2851
- Jörg Florian Liesegang: Gelatine in medicine. Dissertation, University of Heidelberg 2007 (full text) - History of use in medicine in the 17th – 20th centuries Century
- Reinhard Schrieber, Herbert Gareis: Gelatin Handbook. Theory and Industrial Practice. Wiley-VCH, Weinheim 2007, ISBN 978-3-527-31548-2
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