Gelatine (often incorrectly referred to as gelatine ) is a mixture of tasteless animal proteins . The main component is denatured or hydrolyzed collagen , which is produced from the connective tissue of various animal species, particularly pigs and cattle.
Gelatine is the name for jelly made from industrially produced gelatine, in contrast to gelatin (also called aspic ), which is cooked from raw materials rich in animal collagen. The basic recipe is made from broth or water, vinegar and gelatine in leaf or powder form and is used, for. B. used to tie parfaits , not to be confused with galantine .
Gelatine swells in water and dissolves when heated from around 50 ° C. It is a hydrocolloid , in which the gel formed (when cooling) becomes liquid again when heated. This gel / sol transition (see also: sol-gel process ) is thermo reversible and is 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 is hydrolyzed and thus loses its gelling power more and more (measured in Bloom ).
Like all other proteins , gelatin has amphoteric properties. This is why there is a pH value at which the (positive) electrical charge of the amino groups is as great as the (negative) charge of the carboxy groups . This isoelectric point of the gelatine depends on the type of production (acidic digestion: pH 6.0 to 9.5, alkaline digestion: pH 4.7 to 5.6). Gelatin is the least soluble at the isoelectric point. This property can be used when determining the point.
Since hydroxyproline is only contained in significant amounts in gelatine in substance mixtures in the food sector (approx. 13%), the amount of gelatine added can be estimated well by quantitative determination of this amino acid. A differentiation from gelatine is collagen hydrolyzate , which is hydrolyzed by enzymes and sold as a dietary supplement .
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 bouillon in the kitchen) or by treatment with acids and bases and subsequent extraction (industrial production). Gelatine can contain 1–2% inorganic substances and up to 15% water.
Raw material sources
It is expected that around 450,000 tons of gelatine will be produced worldwide in 2018. Edible gelatine used in Europe is made from 80% pork rind (approx. 5 kg pork rinds make 1 kg gelatine). 18% of the gelatine is obtained from animal bones, another 10% from skins. Other raw materials are used to make the remaining portion (2%) of the gelatine.
Fish gelatine is made from the collagen contained in fish skins, u. a. in order to comply with Jewish and Islamic dietary laws (see kosher and halāl ). Allergic reactions to fish are common. On the other hand, there have been no reports of clinical reactions to gelatin in commercially available foods. There are insufficient 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. In 2004, EFSA assessed the data submitted by the Swiss fragrance and flavor manufacturer Givaudan as insufficient. Givaudan had submitted an application for approval of fish gelatine for the encapsulation of flavorings. On the other hand, it was also stated that it was not very likely that fish gelatin would cause a severe allergic reaction in the majority of people with fish allergy under the specified conditions of use.
Industrial manufacturing process
The process used by most manufacturers for the production of gelatine is described as follows: The starting materials for the production of gelatine are connective tissue (skins and bones, cattle split ) from cattle, pigs, fish or poultry. For pretreatment, fat and inorganic constituents are roughly removed from the starting material and the material is crushed (bones are crushed, defatted and freed of calcium carbonate , calcium phosphate and calcium fluoride during maceration ; this demineralised substance is called ossein ). Depending on the starting material, one of two treatment methods is chosen:
- (A) Acid treatment: The material with less cross-linked collagen (e.g. from pork rind) is treated with sulfuric or hydrochloric acid for one day and then neutralized. After intensive washing out of the salts, the collagen is extracted.
- (B) Alkaline treatment: The material with strongly cross-linked collagen (e.g. from cattle) is treated with milk of lime for a period of a few weeks to several months with the formation of ammonia .
The pretreated material is now soluble in warm water ( bouillon ) and is extracted over up to 5 stages with increasing temperature. The temperature determines the gelling power ( Bloom value ): the lower it is, the higher the gelling power; the extraction fractions obtained last at the highest temperature have the lowest gelling power. For cleaning, the extracts are separated from the remaining fat and fibers and filtered. Finally, calcium, sodium, remaining acid residues and other salts are removed.
The thin gelatin solution is thickened in a vacuum dryer to a honey-like consistency. The highly concentrated gelatin solution is sterilized, cooled and dried, during which it gels and the gelled 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% and is still ground into particles of the desired size. 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 belt.
Gelatine is partly used in semi-fat products and light products such as semi-fat margarine, semi-fat butter and low-fat cheeses, as well as a gelling agent for the production of confectionery such as gummy bears , wine gums , soft caramels , marshmallows , foam wafers, liquorice or chocolate kisses . Furthermore, the can in bakery products ( glaze ) and desserts (z. B. Blushing girl , jello , Mädchenröte , whipped cream ) in meat, fish and sausages such as aspic and aspic , mints and Christmas sweets, as well as fining agents in Drinks such as wine, cider, vinegar and all fruit juices that are not naturally cloudy, and in some countries even in beer are used. Fish gelatine has been used as a substitute for lysozyme and casein, especially since the onset of BSE and because of the Jewish dietary laws, to remove sediment and to reduce the proportion of tannin in wine production .
Gelatine can also be used as a means of encapsulating vitamin additives (e.g. in food or effervescent tablets). The vitamins are thus enclosed in a water-soluble manner and dissolve again on contact with liquid.
Gelatin is used to make hard and soft capsules . The medicinal substance, possibly processed with the necessary auxiliary substances, is filled into such gelatin capsules. Gelatine can also be used as a thickening agent to increase the viscosity of liquid medicinal preparations. From the large number of gelatine types, only gelatine A (obtained by acid digestion) or gelatine B (obtained by alkaline digestion) are used in practice. In medical technology , gelatine is used, among other things, to coat implants such as vascular prostheses .
Bovine gelatine in the form of polygelin as a stabilizer is or was contained in several vaccines , such as those against TBE , Japanese encephalitis , rabies , varicella and in the MMR vaccine . Although allergic reactions to vaccines with a frequency of around 1 reaction to 500,000 vaccine doses are rare, allergy to gelatin (in combination with thiomersal ) as an allergic reaction of the immediate type (up to anaphylaxis ) plays an important role and applies to around half of them responsible for all related complications, so this is now increasingly being removed from vaccines.
In emergency medicine , gelatine is used as a so-called volume replacement for the treatment of volume deficiency shock. Gelatine sponges, which are absorbed by the body, are also used to stop bleeding during and after operations. They can absorb up to 45 times their own weight in blood and serve as a cellular framework for wound healing .
Even in the early days of photography , gelatine was used in the so-called dry gelatine process. Gelatine is contained in the usual photographic films and photo papers , in some photographic high-quality printing processes it is the carrier of the pigment or chemical layer . Many photo printing papers for inkjet printing also have a gelatine coating and are therefore often used by manufacturers of classic photo papers manufactured.
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 often made of gelatine. In the sport of paintball, it is also used as a cover for biodegradable ammunition. For the determination of weft ducts or the depth of penetration of a projectile is ballistic gelatin used.
In violin making, gelatine is applied directly to the wood as a primer after heating in a water bath, in order to ensure an even tint of the wood during later staining.
In addition to gelatine, the production of gelatine also produces by-products that are used further: meat bone meal ( e.g. as animal feed or fertilizer ), bone fat ( e.g. for soap production ) and calcium carbonate (e.g. for toothpaste production ). Metals, adhesives and particularly strong paper can also be produced with the help of gelatine.
The results of the substitute processes vary greatly in their comparability with gelatine products.
Herbal thickeners and gelling agents are mostly polysaccharides , e.g. B. from various algae isolated alginates , carrageenans and agar agar, furthermore also pectin from fruits, gum arabic , starch of various origin, guar gum , xanthan gum and locust bean gum .
Alternative methods of clarifying liquids work with clay , tannin , diatomite or asbestos . Instead of gelatin, however, are also casein (from milk), chitin (from fishing-waste production and biotechnology) and isinglass (a sturgeon swim bladder) is used. If gelatine is used as an auxiliary in production, it does not have to be declared as an ingredient. In these cases, their use can only be clarified, if at all, through direct product inquiries to the manufacturer. Gelatine-free products can sometimes be used for products from the pharmaceutical industry and other industries.
- W. Babel: Gelatine - a versatile biopolymer. In: Chemistry in our time , 30, 1996, pp. 86-95; doi: 10.1002 / ciuz.19960300205 .
- Jörg Florian Liesegang: Gelatine in Medicine: History of the use of gelatine in medicine from the end of the 17th to the beginning of the 20th century. Dissertation . University of Heidelberg, 2007. urn : nbn: de: bsz: 16-opus-77577
- Reinhard Schrieber, Herbert Gareis: Gelatine Handbook. Theory and Industrial Practice . Wiley-VCH, Weinheim 2007, ISBN 978-3-527-31548-2 .
- Information. ( Memento from April 12, 2008 in the Internet Archive ) Uni Bayreuth
- Website of the Association of European Gelatine Manufacturers
- Incorrect spelling on duden.de
- F. Jürgen Herrmann: Textbook for cooks . Handwerk und Technik, Hamburg 1999, ISBN 3-582-40055-7 , p. 289 .
- Global Gelatin Market Projected to Reach $ 2.79 Trillion in 2018; The global gelatin market was worth $ 1.77 billion in 2011 and is expected to grow at a CAGR of 6.75% from 2012 to 2018 ( Memento from June 5, 2016 in the Internet Archive )
- Gelatine market data (Gelatine Manufacturer of Europe) ( Memento from October 16, 2013 in the Internet Archive ; PDF; 1.7 MB)
- The Manufacturing Process. Gelatine Manufacturers of Europe.
- Council on Pharmacy and Chemistry: Absorbable Gelatin sponge - new and nonofficial remedies . In: JAMA , 135, 1947, p. 921.