|CAS number||9005-25-8, 9005-84-9|
|Monomer||D - glucose|
|Molecular formula of the repeating unit||C 6 H 10 O 5|
|Molar mass of the repeating unit||162.14 g mol −1|
|Type of polymer||
colorless and odorless powder
200 ° C (decomposition)
insoluble in cold water
|As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .|
Starch (Latin: amylum ) is an organic compound . It is a polysaccharide with the formula (C 6 H 10 O 5 ) n , which consists of α- D - glucose units. The macromolecule is therefore one of the carbohydrates . Starch is one of the most important reserves in plant cells , while the animal or human organism and fungi use glycogen as a carbohydrate store.
Starch is a product of the assimilation of carbon dioxide (see Calvin cycle ). Normally it is present in the plant cell in the form of organized starch grains, depending on the plant species in different sizes and shapes. They can be spherical, oval, lenticular or spindle-shaped, sometimes, as in the milky sap of the Euphorbiaceae , also rod-like with swollen ends. Sometimes they are polyhedral due to mutual pressure . Often several grains come together to form a rounded whole (composite starch grains).
The structure of starch is similar to that of glycogen , the storage substance in animal cells. Starch molecules consist of D - glucose units that are linked to one another via glycosidic bonds. There is usually too much strength
- 20–30% amylose , linear chains with a helical (screw) structure that are only linked α-1,4-glycosidically and
- 70–80% amylopectin , strongly branched structures, with α-1,6-glycosidic and α-1,4-glycosidic linkages. The amylopectin of starch, however, with about an α-1,6-glycosidic bond after about 30 α-1,4-glycosidic linkages, is less branched than that of the glycogen (approx. 1 α-1,6-glycosidic per 10 α- 1,4-glycosidic bonds).
In exceptional cases, the proportions can also differ, for example so-called sticky rice almost exclusively contains amylopectin.
Starch grains lying in the water reveal a clear stratification, which is caused by the fact that around an inner, less dense part, the so-called formation center, layers of uneven light refraction are stored in a shell-like manner; The center of formation is only exactly in the center (concentric) in the case of spherical grains, it is mostly eccentric, and the layers surrounding it are accordingly of unequal thickness. The stratification is caused by the different water content and the resulting different refraction of light of the layers, which is why dry grains or grains lying in absolute ethanol appear uncoated. In polarized light , all starch grains show a bright, four-armed cross, the center of which coincides with the center of the stratification; they therefore behave as if they were composed of uniaxial crystal needles.
Proof of strength
Normally starch using iodine -containing Lugolschen solution in an iodine sample demonstrated (first Henri-François Gaultier de Claubry , JJ Colin 1814). The amylose contained in starch is detected with a characteristic blue color. The blue color arises in a reversible equilibrium reaction through the inclusion of iodine in the amylose dissolved in water. At low concentrations (pale blue coloration) it is possible to shift the equilibrium back to the side of the uncomplexed colorless amylose by heating.
In addition, starch can be detected with the help of a polarimeter by breaking the starch by boiling with acid and filtering it after adding Carrez I and II . The optical rotation can then be determined on the polarimeter, which provides an indication of the amount of starch.
Starch as a vegetable storage substance
|Raw material plant||Starch content
(in% of the plant parts used)
Plants and green algae use starch to store their excess energy as a reserve. The purpose of starch formation is to store the glucose in an insoluble and thus osmotically ineffective form. Compared to glucose, starch can therefore be stored without much water, i.e. much more compactly. The starch occurs in the most diverse tissues of all green plants. While a form of starch that varies somewhat in terms of the degree of branching also occurs in red algae (so-called Florideophycean starch), most other organisms use other reserve substances ( diatoms , golden algae and brown algae : chrysolaminarin ; Euglena: paramylon ; Cryptophyceae : oils in the cytoplasm, starch in the periplastid arena Room).
Also in the epidermal cells of some higher plants there is a substance which turns blue or reddish with iodine in dissolved form, the soluble starch. In all other cases, the starch appears in the granular form described as a rule. The tissues of the seeds , tubers , bulbs and rhizomes, as well as the wood rays and the wood parenchyma in the wood body of the trees, are very rich in starch . This reserve starch differs in its large grain size from the fine-grain starch occurring in the assimilating tissue. The starch is formed either within the chloroplasts or in other plastids , for example in the colorless leucoplasts . The latter occur particularly in such chlorophyll-free tissues in which the assimilation products are converted into reserve starch, as in many bulbs containing starch. With many algae containing chlorophyll , e.g. B. in Spirogyra , the starch grains occur in special centers of formation in the vicinity of pyrenoids . The growth of the initially very tiny starch grains takes place through the storage of new starch molecules between the already existing ones, while the composite starch grains are formed by subsequent fusion and rearrangement with new layers.
The biosynthesis and storage of starch takes place in the amyloplasts . First, glucose-1-phosphate is activated by ATP from the enzyme glucose-1-phosphate adenylyl transferase to ADP-glucose. The starch synthase enzyme then adds the activated ADP-glucose monomers α-1,4-glycosidically to the growing amylose chain, splitting off ADP. The α-1,6-glycosidic branches of amylopectin are then produced by the starch-branching enzyme ( 1,4-α-glucan-branching enzyme ) by splitting off seven glucose residues of an α-1,4-glycosidic chain at least eleven residues long and α-1,6-glycosidically attached to a glucose molecule of the chain.
Splitting of strengths
Starch can be broken down by enzymes (α-, β- amylases ). This creates dextrins or disaccharides . This happens e.g. B. also inside plant cells, because in the life of the plant the starch provides z. B. the material for building the cell wall . Similarly, the animal and human bodies can get energy from starch. In contrast, resistant starch is inaccessible to the digestive enzymes. Amylases are also used as flour treatment agents to make flours more bakeable . In the case of rye in particular, however , the breakdown of starch as a result of natural amylase activity must generally be curbed in order to ensure that it can be baked. Traditionally, this is done by acidifying the dough .
Behavior during heating (gelatinization)
Under the influence of heat, starch can physically bind, swell and gelatinize many times its own weight in water . When heated with water, the starch swells at 47-57 ° C, the layers burst, and at 55-87 ° C ( potato starch at 62.5 ° C, wheat starch at 67.5 ° C), starch paste is formed, which depends on the type of starch has different stiffness (corn starch paste is greater than wheat starch paste, this is greater than potato starch paste) and decomposes more or less easily when acidified. In a cool environment, this effect slowly regresses - one speaks of retrogradation . Gelatinized starch and coagulated gluten form the basic structure or crumb of all types of baked goods.
According to current (2004) knowledge, when starches are overheated, especially when baking, roasting , roasting , grilling and deep-frying , the possibly carcinogenic acrylamide is formed in the presence of the amino acid asparagine .
In Europe, starch used to be mostly obtained from potatoes or grain , today corn is the dominant starch supplier. In 1979, with a world production of 13 million tons, 76% came from corn, 15% from potatoes, 4% from cassava and 3% from wheat.
Rice (broken rice from the rice peeling factories) and manioc ( tapioca ) are also of international importance as starch-producing plants. In Japanese cuisine , kudzu (kuzuko) and Japanese dog's tooth (katakuriko) are also used. Various technologies are used in industrial starch production, depending on the raw material. The processing of the delivered raw material begins with the cleaning, continues with the comminution and separation of the components (starch, protein and fibers) and ends with the cleaning, dehydration and drying of the starch.
Historical methods of starch production
Potato starch ( lat.amylum solani )
Potatoes contain around 75% water, 21% starch and 4% other substances. For the production of potato starch , they are traditionally ground as finely as possible on rapidly rotating cylinders fitted with saw teeth under the inflow of water. Then the pulp - in which the cells should be torn as completely as possible, the starch grains should be exposed - is then washed out with water on a metal sieve, on which the brushes rotate slowly. In larger companies continuously operating devices are used in which the pulp is gradually transported by a chain over a long inclined sieve and washed out in the process. The water flowing out of the almost exhausted pulp at the end of the sieve, which contains very little cornstarch, is returned to fresh pulp for maximum use. The washed-out pulp contains 80–95% water, but still about 60% starch in the dry matter and is used as fodder, also for starch sugar, brandy and paper production; the washing water was used to sprinkle the meadows, but it was also possible to use the nitrogenous components of the potato fruit water as fodder. Since the pulp still contains a great deal of starch, it is rubbed between rollers to open all the cells and then washed out again. According to another method, the potatoes are cut into slices, their juice is removed by maceration in water and they are piled up in piles with brushwood or trays, in which they rot completely in about eight days at a temperature of 30–40 ° C a loose, pulpy mass can be transformed from which the starch can be easily washed out. The water draining from the sieves contains the potato juice components dissolved and the starch and fine fibers that have passed through the sieve suspended. This water is stirred up in vats, left to stand for a short time so that sand and small stones can fall to the ground, then let it flow through a fine sieve to hold back coarser fibers, and then put it in a vat where the Starch and on it the fiber is deposited. The upper layer of the sediment is therefore removed after the water has been drained and used directly as starch sludge or further cleaned by washing it with plenty of water on a shaking sieve made of fine silk gauze, through the mesh of which the starch but not the fibers pass. The main mass of the starch is repeatedly mixed with pure water in the vat and freed from the top impure starch each time it has settled. You can also let the raw starch with water flow through a very slightly inclined channel, in the upper part of which the heavy pure starch is deposited, while the lighter fibers are carried on by the water.
Centrifugal machines are also often used, in which the heavy starch is initially deposited on the vertical wall of the rapidly rotating sieve drum, while the light fiber remains suspended in the water. The water escapes through the sieve wall and the starch can finally be lifted out of the centrifugal machine in solid blocks, the inner layer of which is the fiber. The moist (green) starch, which contains about 33-45% water, is easily processed into glucose, but for all other purposes on filter presses or on plates of plaster of paris that eagerly suck in water, dehydrated using the air pump and with dried at a temperature below 60 ° C. They are sold in chunks or, crushed between rollers and sifted, as flour. Sometimes the moist starch is kneaded with a little paste and driven through a perforated iron plate, whereupon the stalks obtained are dried on trays. To cover up a yellowish shade of starch, a little ultramarine is added to it before the last wash .
Wheat starch (Latin Amylum Tritici )
Wheat starch is made from white, thin-shelled, floury wheat . This contains about 58-64% starch, also about 10% glue and 3-4% pulp, which mainly forms the husks of the grain. The properties of the glue cause the deviations in wheat starch production from the production of starch from potatoes. According to the traditional Halleschen or sour process, the wheat is soaked in water, crushed between rollers and, doused with water, left to fermentation, which is initiated by sour water from an earlier process and provides acetic and lactic acid, in which the glue dissolves or at least loses its tough consistency to such an extent that after 10-20 days the starch can be separated in a sieve-like perforated washing drum. The water flowing out of the drum first deposits starch in a vat, then an intimate mixture of starch with glue and sleeve particles (size, sludge starch), and finally a muddy mass consisting mainly of glue. This raw starch is cleaned in a similar way to potato starch and then dried, whereby it disintegrates into powder or, if it still contains small amounts of glue, supplies what is known as radiation strength, which normal consumers mistakenly consider particularly pure.
According to the traditional Alsatian method, the swollen wheat is crushed by upright millstones under a strong flow of water and washed out immediately. In addition to starch, the draining water contains a lot of glue and husk particles and is either left to ferment and then processed further as in the previous process, or taken directly to centrifugal machines, where a lot of glue is separated and a raw starch is obtained, which is further purified through fermentation etc. The residues obtained in this process have a considerably higher agricultural value than those resulting from the Halle process. But if you want to use the glue even more advantageously, you make a firm, tough dough out of wheat flour and work it after about an hour in pieces of 1 kg in a channel-shaped trough under the inflow of water with a lightly fluted roller. The starch is washed out of the adhesive and flows off with the water, while the adhesive remains as a tough, stringy mass.
Rice starch ( lat.amylum oryzae )
Rice contains 70–75% starch and 7–9% insoluble, protein-like substances, which are largely dissolved by soaking the rice in very weak sodium hydroxide solution. The rice is then grinded in a mill with a constant flow of weak lye, treated the pulp in a vat with lye and water, allowed to settle for a short time so that the coarser parts sink to the bottom, and the water, in which pure starch is suspended, is drawn off , from. The starch is washed out of the sediment in a rotating sieve cylinder with water, whereupon it is freed from the glue by treating with lye and sludge. The purer starch obtained first is allowed to settle, the upper impure layer is removed, the rest is treated on the centrifugal machine and the pure starch is dried.
Corn starch (Latin Amylum Maydis )
Corn is soaked four to five times for 24 hours in water at 35 ° C, washed and then allowed to go through two grinding cycles. The flour falls into a water-filled vat with a paddle stirrer and from there it reaches the silk fabric, which only holds back the coarse bran. The water loaded with the starch that has passed through the fabric gets into troughs, then through two fine fabrics and finally onto slightly inclined, 80-100 m long slates on which the starch is deposited. The draining water, which only contains traces of starch, is left to stand and the heel is pressed into cake to be used as fodder.
Horse chestnut starch
Starch can also be obtained from horse chestnuts , but it can only be used for technical purposes, since any bitter substance adhering to it can hardly be completely removed by treatment with sodium carbonate . The yield is 19-20%. The commercial starch, on the other hand, contains around 80–84% pure starch, 14–18% water and in the cheaper varieties up to 5% glue, 2.5% fibers and 1.3% ash , while the ash content in the best varieties is only 0, 01%.
The main part of starch and its products is used in the food industry in the production of confectionery, baked goods, dairy products and especially beverages in the form of starch-based sugars (mainly glucose syrup , dextrose and isoglucose ). According to the German Association of the Starch Industry, this share is currently 55% of the 1.9 million tons available in Germany. Due to the properties of starch as a modifiable polymer and its composition of fermentable sugar units, starch is also used in a variety of ways as a renewable raw material in the chemical-technical industry; According to the association, the consumption of starch and starch derivatives in Germany in 2007 was 45% and thus more than 850,000 t. About 4.5% of the amount went to the chemical and fermentation industries, 95.5% was used in paper and corrugated cardboard production. Chemical applications are diverse, but in total rare and the use in fermentation is relatively low compared to sucrose (as thick juice and molasses ).
The following starch products are listed in the food lexicon of Ternes, Täufel, Tunger and Zobel:
- Starch fractions
- deformed strength
- without heat
- Chunk strength
- Radiation strength
- with heat
- Flake starch
- Swelling starch (instant starch)
- without heat
Sago / tapioca
- Pearl sago
- Pearl tapioca
- partially depleted starch
- Hydrolysis products
- Starch ester
- Starch ether
Use in the food industry
As native and modified starch, starch is used in a variety of ways in the food industry. Starchy plants such as potatoes , wheat , maize and cassava are the most important staple foods for the supply of carbohydrates internationally . In addition, there are pasta , bread and other baked goods , for the production of which flour from various types of starchy grain such as wheat, rye or barley is used. In addition, starch is used to produce various starch-based sugars such as dextrins , grape sugar , maltodextrin and glucose syrup , which is used as a sweetener in the entire food industry (e.g. lemonades , ice cream , jams , confectionery ), but with e.g. Partly controversial consequences (see corn syrup ).
Individual types of starch (such as potato starch or corn starch) also serve as an ingredient in numerous cooking recipes and in the food industry, where the starch is often used in the form of modified starch (see thickeners ). Starch is the most important thickener in the food industry and is used e.g. B. used in ready meals.
Use in industry and as a material
→ Main article: Starch as a renewable raw material
Starch, especially in the form of potato starch, corn starch and wheat starch, is one of the most important renewable raw materials due to its diverse applications in the chemical-technical industry, alongside wood and sugar (sucrose) . The main areas of application for starch are in the production of paper and corrugated cardboard as paper starch and in the fermentation industry as a fermentable substrate for the production of various platform chemicals and bioethanol as a biofuel . In the USA, corn starch is the main raw material for bioethanol. According to information from the German bioethanol industry in 2009 (BDB 2009), the majority of bioethanol in Germany is also obtained from starchy plants, especially wheat. In some other countries, the biofuel is mainly obtained from sugar, for example in Brazil from the cultivation of sugar cane .
Strength is also used for pickling of cotton , for staining with aniline dyes , for sizing paper , and to thicken colors in the textile printing . In offset printing , a starch powder-air mixture, often made from corn, is applied to the freshly printed surface using powder machines . The powder acts as a spacer between the stacked sheets of paper and promotes the oxidative drying of the printing ink because of the enclosed air .
Relatively new is the material use as bio-based plastic in the form of so-called thermoplastic starch z. B. for compostable disposable crockery and cutlery or as a foamed upholstery material in packages (starch thermoset). In the pharmaceutical industry, starch is used in the manufacture of tablets , where it can serve as a filler , disintegrant and binder , and as a powder base .
Use in medicine
Uncooked corn starch plays an important role in the treatment of glycogen storage diseases . With some of these metabolic disorders , hypoglycaemia occurs after a short time without ingesting food , as the release of glycogen stores from the liver is impaired. Uncooked corn starch is digested particularly slowly and can therefore support the blood sugar level for several hours. In addition to the common household cornstarch products, medicinal products made from modified corn starch are also used, which release energy even more slowly.
Prehistory and history
Contrary to popular beliefs about Stone Age nutrition (Paleo diet), people and their ancestors such as Australopithecus sometimes used starchy parts of plants such as millet grains even before the Paleolithic . The contribution of starch in nutrition is considered essential to human evolution . The rhizomes of the African Hypoxis angustifolia are considered early suppliers of starch (170,000 years ago) . Early evidence of starch use from Europe is dated 30,000 years ago. Strength has been used by people on all continents. A particularly old millstone (around 27,000 years old) comes from the Cuddie Springs site in Southeast Australia.
In the Middle Ages , starch was produced on a large scale in the Netherlands in the 16th century, and significant quantities were exported. Isolated instructions for the production of starch in the 15th and 16th centuries are in a Wolfenbüttel manuscript ( Codex Guelferbytanus 16.17. Aug. 4 ° ; after 1415), in an English cookbook from the 15th century and in the cookbook by Balthasar Standl (1569) contain. The starch industry developed primarily as an agricultural trade. With the simplest devices one gained only a moderate yield, but the advances in the perfecting of the machines and apparatus then led to a greater yield, above all through the introduction of specially designed centrifugal machines. In Schleswig-Holstein, starch made from grain was called amidam (from Middle Latin amidum ) and was used not only as an adhesive but also, for example, as a hair powder. In 1840 the production volume of the 20 existing amidam factories in Schleswig-Holstein was 180 tons per year. In the 18th and 19th centuries, the Lübeck Amidam was considered a special quality product throughout Europe.
- AGRANA starch GmbH (starch from potatoes, maize, waxy maize and wheat)
- AVEBE (potato starch)
- Blattmann Schweiz AG (wheat starch and potato starch)
- Cargill (incl. Cerestar )
- Chamtor (wheat starch)
- Crespel & Deiters (wheat starch)
- Emsland Group (potato starch)
- Jäckering Mühlen- und Nahrungsmittelwerke GmbH (wheat starch)
- KMC (potato starch)
- Kröner starch / Hermann Kröner GmbH (wheat starch)
- Lyckeby (potato starch)
- Ingredion (formerly National Starch and American Corn Products International (CPI) )
- Remy Industries (rice starch)
- Roquette Frères (potato / corn / wheat / pea starch)
- Interstarch GmbH (wheat starch)
- Südstark GmbH (potato starch)
- Syral / Tereos (corn / wheat starch)
- Tate & Lyle (wheat starch and potato starch)
- Former Hoffmann's starch factories in Bad Salzuflen (potato, rice and wheat starch)
- Former R. Hundhausen starch factory in Hamm , later in Ahlen / Westf. (Wheat starch)
- Zulkowsky soluble starch
- Corn syrup
- Native strength
- Physically modified starch
- Laundry starch
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