Starch

Starch or amylum is a polymeric carbohydrate consisting of a large number of glucose units joined by glycosidic bonds. This polysaccharide is produced by most green plants as energy storage. It is the most common carbohydrate in human diets and is contained in large amounts in staple foods like potatoes, wheat, maize (corn), rice, and cassava.

Pure starch is a white, tasteless and odorless powder that is insoluble in cold water or alcohol. It consists of two types of molecules: the linear and helical amylose and the branched amylopectin. Depending on the plant, starch generally contains 20 to 25% amylose and 75 to 80% amylopectin by weight.[4] Glycogen, the glucose store of animals, is a more highly branched version of amylopectin.

In industry, starch is converted into sugars, for example by malting, and fermented to produce ethanol in the manufacture of beer, whisky and biofuel. It is processed to produce many of the sugars used in processed foods. Mixing most starches in warm water produces a paste, such as wheatpaste, which can be used as a thickening, stiffening or gluing agent. The biggest industrial non-food use of starch is as an adhesive in the papermaking process. Starch can be applied to parts of some garments before ironing, to stiffen them.

Starch
Cornstarch being mixed with water
Identifiers
ChemSpider
  • none
ECHA InfoCard 100.029.696
EC Number 232-679-6
RTECS number GM5090000
Properties
(C
6
H
10
O
5
)
n -
(H
2
O)
Molar mass Variable
Appearance White powder
Density Variable[1]
Melting point decomposes
insoluble (see starch gelatinization)
Thermochemistry
4.1788 kilocalories per gram (17.484 kJ/g)[2] (Higher heating value)
Hazards
Safety data sheet ICSC 1553
410 °C (770 °F; 683 K)
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)[3]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Amylose2
Structure of the amylose molecule
Amylopektin Sessel
Structure of the amylopectin molecule

Etymology

The word "starch" is from a Germanic root with the meanings "strong, stiff, strengthen, stiffen".[5] Modern German Stärke (strength) is related. The Greek term for starch, "amylon" (ἄμυλον), is also related. It provides the root amyl, which is used as a prefix for several 5-carbon compounds related to or derived from starch (e.g. amyl alcohol).

History

Starch grains from the rhizomes of Typha (cattails, bullrushes) as flour have been identified from grinding stones in Europe dating back to 30,000 years ago.[6] Starch grains from sorghum were found on grind stones in caves in Ngalue, Mozambique dating up to 100,000 years ago.[7]

Pure extracted wheat starch paste was used in Ancient Egypt possibly to glue papyrus.[8] The extraction of starch is first described in the Natural History of Pliny the Elder around AD 77–79.[9] Romans used it also in cosmetic creams, to powder the hair and to thicken sauces. Persians and Indians used it to make dishes similar to gothumai wheat halva. Rice starch as surface treatment of paper has been used in paper production in China since 700 CE.[10]

Starch industry

In addition to starchy plants consumed directly, by 2008 66 million tonnes of starch were being produced per year worldwide. In 2011 production was increased to 73 million ton. [11]]

In the EU the industry produced abount 8.5 million tonnes in 2008, with around 40% being used for industrial applications and 60% for food uses,[12] most of the latter as glucose syrups.[13] In 2017 EU production was 11 million ton of which 9,4 million ton was consumed in the EU and of which 54% were starch sweeteners.[14]

US produced about 27,5 million ton starch in 2017 of which about 8,2 million ton high fructose syrup and 6,2 million ton glucose syrups and 2,5 million ton starch products, the rest of the starch was used for producing ethanol (1,6 billion gallon or 7,3 billion liter of ethanol). [15][16]

Energy store of plants

Most green plants use starch as their energy store.The extra glucose is changed into starch which is more complex than glucose(by plants). An exception is the family Asteraceae (asters, daisies and sunflowers), where starch is replaced by the fructan inulin. Inulin-like fructans are also present in grasses such as wheat, in onions and garlic, bananas, and asparagus.[17]

In photosynthesis, plants use light energy to produce glucose from carbon dioxide. The glucose is used to generate the chemical energy required for general metabolism, to make organic compounds such as nucleic acids, lipids, proteins and structural polysaccharides such as cellulose, or is stored in the form of starch granules, in amyloplasts. Toward the end of the growing season, starch accumulates in twigs of trees near the buds. Fruit, seeds, rhizomes, and tubers store starch to prepare for the next growing season.

Glucose is soluble in water, hydrophilic, binds with water and then takes up much space and is osmotically active; glucose in the form of starch, on the other hand, is not soluble, therefore osmotically inactive and can be stored much more compactly.

Glucose molecules are bound in starch by the easily hydrolyzed alpha bonds. The same type of bond is found in the animal reserve polysaccharide glycogen. This is in contrast to many structural polysaccharides such as chitin, cellulose and peptidoglycan, which are bound by beta bonds and are much more resistant to hydrolysis.[18]

Biosynthesis

Plants produce starch by first converting glucose 1-phosphate to ADP-glucose using the enzyme glucose-1-phosphate adenylyltransferase. This step requires energy in the form of ATP. The enzyme starch synthase then adds the ADP-glucose via a 1,4-alpha glycosidic bond to a growing chain of glucose residues, liberating ADP and creating amylose. The ADP-glucose is almost certainly added to the non-reducing end of the amylose polymer, as the UDP-glucose is added to the non-reducing end of glycogen during glycogen synthesis.[19]

Starch branching enzyme introduces 1,6-alpha glycosidic bonds between the amylose chains, creating the branched amylopectin. The starch debranching enzyme isoamylase removes some of these branches. Several isoforms of these enzymes exist, leading to a highly complex synthesis process.[20]

Glycogen and amylopectin have similar structure, but the former has about one branch point per ten 1,4-alpha bonds, compared to about one branch point per thirty 1,4-alpha bonds in amylopectin.[21] Amylopectin is synthesized from ADP-glucose while mammals and fungi synthesize glycogen from UDP-glucose; for most cases, bacteria synthesize glycogen from ADP-glucose (analogous to starch).[22]

In addition to starch synthesis in plants, starch can be synthesized from non-food starch mediated by an enzyme cocktail.[23] In this cell-free biosystem, beta-1,4-glycosidic bond-linked cellulose is partially hydrolyzed to cellobiose. Cellobiose phosphorylase cleaves to glucose 1-phosphate and glucose; the other enzyme—potato alpha-glucan phosphorylase can add a glucose unit from glucose 1-phosphorylase to the non-reducing ends of starch. In it, phosphate is internally recycled. The other product, glucose, can be assimilated by a yeast. This cell-free bioprocessing does not need any costly chemical and energy input, can be conducted in aqueous solution, and does not have sugar losses.[24][25][26]

Degradation

Starch is synthesized in plant leaves during the day and stored as granules; it serves as an energy source at night. The insoluble, highly branched starch chains have to be phosphorylated in order to be accessible for degrading enzymes. The enzyme glucan, water dikinase (GWD) phosphorylates at the C-6 position of a glucose molecule, close to the chains 1,6-alpha branching bonds. A second enzyme, phosphoglucan, water dikinase (PWD) phosphorylates the glucose molecule at the C-3 position. A loss of these enzymes, for example a loss of the GWD, leads to a starch excess (sex) phenotype,[27] and because starch cannot be phosphorylated, it accumulates in the plastids.

After the phosphorylation, the first degrading enzyme, beta-amylase (BAM) can attack the glucose chain at its non-reducing end. Maltose is released as the main product of starch degradation. If the glucose chain consists of three or fewer molecules, BAM cannot release maltose. A second enzyme, disproportionating enzyme-1 (DPE1), combines two maltotriose molecules. From this chain, a glucose molecule is released. Now, BAM can release another maltose molecule from the remaining chain. This cycle repeats until starch is degraded completely. If BAM comes close to the phosphorylated branching point of the glucose chain, it can no longer release maltose. In order for the phosphorylated chain to be degraded, the enzyme isoamylase (ISA) is required.[28]

The products of starch degradation are predominantly maltose[29] and smaller amounts of glucose. These molecules are exported from the plastid to the cytosol, maltose via the maltose transporter, which if mutated (MEX1-mutant) results in maltose accumulation in the plastid.[30] Glucose is exported via the plastidic glucose translocator (pGlcT).[31] These two sugars act as a precursor for sucrose synthesis. Sucrose can then be used in the oxidative pentose phosphate pathway in the mitochondria, to generate ATP at night.[28]

Properties

Structure

Stärkemehl 800 fach Polfilter
Starch, 800x magnified, under polarized light, showing characteristic extinction cross
Rice starch - microscopy
Rice starch seen on light microscope. Characteristic for the rice starch is that starch granules have an angular outline and some of them are attached to each other and form larger granules

While amylose was thought to be completely unbranched, it is now known that some of its molecules contain a few branch points.[32] Amylose is a much smaller molecule than amylopectin. About one quarter of the mass of starch granules in plants consist of amylose, although there are about 150 times more amylose than amylopectin molecules.

Starch molecules arrange themselves in the plant in semi-crystalline granules. Each plant species has a unique starch granular size: rice starch is relatively small (about 2 μm) while potato starches have larger granules (up to 100 μm).

Starch becomes soluble in water when heated. The granules swell and burst, the semi-crystalline structure is lost and the smaller amylose molecules start leaching out of the granule, forming a network that holds water and increasing the mixture's viscosity. This process is called starch gelatinization. During cooking, the starch becomes a paste and increases further in viscosity. During cooling or prolonged storage of the paste, the semi-crystalline structure partially recovers and the starch paste thickens, expelling water. This is mainly caused by retrogradation of the amylose. This process is responsible for the hardening of bread or staling, and for the water layer on top of a starch gel (syneresis).

Some cultivated plant varieties have pure amylopectin starch without amylose, known as waxy starches. The most used is waxy maize, others are glutinous rice and waxy potato starch. Waxy starches have less retrogradation, resulting in a more stable paste. High amylose starch, amylomaize, is cultivated for the use of its gel strength and for use as a resistant starch (a starch that resists digestion) in food products.

Synthetic amylose made from cellulose has a well-controlled degree of polymerization. Therefore, it can be used as a potential drug deliver carrier.[23]

Certain starches, when mixed with water, will produce a non-newtonian fluid sometimes nicknamed "oobleck".

Hydrolysis

The enzymes that break down or hydrolyze starch into the constituent sugars are known as amylases.

Alpha-amylases are found in plants and in animals. Human saliva is rich in amylase, and the pancreas also secretes the enzyme. Individuals from populations with a high-starch diet tend to have more amylase genes than those with low-starch diets;[33]

Beta-amylase cuts starch into maltose units. This process is important in the digestion of starch and is also used in brewing, where amylase from the skin of seed grains is responsible for converting starch to maltose (Malting, Mashing).[34][35]

Given a heat of combustion of glucose of 2,805 kilojoules per mole (670 kcal/mol) whereas that of starch is 2,835 kJ (678 kcal)[2] per mole of glucose monomer, hydrolysis releases about 30 kJ (7.2 kcal) per mole, or 166 J (40 cal) per gram of glucose product.

Dextrinization

If starch is subjected to dry heat, it breaks down to form dextrins, also called "pyrodextrins" in this context. This break down process is known as dextrinization. (Pyro)dextrins are mainly yellow to brown in color and dextrinization is partially responsible for the browning of toasted bread.[36]

Chemical tests

Wheat starch granules
Granules of wheat starch, stained with iodine, photographed through a light microscope

A triiodide (I3) solution formed by mixing iodine and iodide (usually from potassium iodide) is used to test for starch; a dark blue color indicates the presence of starch. The details of this reaction are not fully known, but recent scientific work using single crystal x-ray crystallography and comparative Raman spectroscopy suggests that the final starch-iodine structure is similar to an infinite polyiodide chain like one found in a pyrroloperylene-iodine complex.[37] The strength of the resulting blue color depends on the amount of amylose present. Waxy starches with little or no amylose present will color red. Benedict's test and Fehling's test is also done to indicate the presence of starch.

Starch indicator solution consisting of water, starch and iodide is often used in redox titrations: in the presence of an oxidizing agent the solution turns blue, in the presence of reducing agent the blue color disappears because triiodide (I3) ions break up into three iodide ions, disassembling the starch-iodine complex. Starch solution was used as indicator for visualizing the periodic formation and consumption of triiodide intermediate in the Briggs-Rauscher oscillating reaction. The starch, however, changes the kinetics of the reaction steps involving triiodide ion[38]. A 0.3% w/w solution is the standard concentration for a starch indicator. It is made by adding 3 grams of soluble starch to 1 liter of heated water; the solution is cooled before use (starch-iodine complex becomes unstable at temperatures above 35 °C).

Each species of plant has a unique type of starch granules in granular size, shape and crystallization pattern. Under the microscope, starch grains stained with iodine illuminated from behind with polarized light show a distinctive Maltese cross effect (also known as extinction cross and birefringence).

Food

Starch is the most common carbohydrate in the human diet and is contained in many staple foods. The major sources of starch intake worldwide are the cereals (rice, wheat, and maize) and the root vegetables (potatoes and cassava).[39] Many other starchy foods are grown, some only in specific climates, including acorns, arrowroot, arracacha, bananas, barley, breadfruit, buckwheat, canna, colacasia, katakuri, kudzu, malanga, millet, oats, oca, polynesian arrowroot, sago, sorghum, sweet potatoes, rye, taro, chestnuts, water chestnuts and yams, and many kinds of beans, such as favas, lentils, mung beans, peas, and chickpeas.

Widely used prepared foods containing starch are bread, pancakes, cereals, noodles, pasta, porridge and tortilla.

Digestive enzymes have problems digesting crystalline structures. Raw starch is digested poorly in the duodenum and small intestine, while bacterial degradation takes place mainly in the colon. When starch is cooked, the digestibility is increased.

Starch gelatinization during cake baking can be impaired by sugar competing for water, preventing gelatinization and improving texture.

Before the advent of processed foods, people consumed large amounts of uncooked and unprocessed starch-containing plants, which contained high amounts of resistant starch. Microbes within the large intestine fermented the starch, produced short-chain fatty acids, which are used as energy, and support the maintenance and growth of the microbes. More highly processed foods are more easily digested and release more glucose in the small intestine—less starch reaches the large intestine and more energy is absorbed by the body. It is thought that this shift in energy delivery (as a result of eating more processed foods) may be one of the contributing factors to the development of metabolic disorders of modern life, including obesity and diabetes.[40]

Starch production

The starch industry extracts and refines starches from seeds, roots and tubers, by wet grinding, washing, sieving and drying. Today, the main commercial refined starches are cornstarch, tapioca, arrowroot,[41] and wheat, rice, and potato starches. To a lesser extent, sources of refined starch are sweet potato, sago and mung bean. To this day, starch is extracted from more than 50 types of plants.

Untreated starch requires heat to thicken or gelatinize. When a starch is pre-cooked, it can then be used to thicken instantly in cold water. This is referred to as a pregelatinized starch.

Starch sugars

Starch can be hydrolyzed into simpler carbohydrates by acids, various enzymes, or a combination of the two. The resulting fragments are known as dextrins. The extent of conversion is typically quantified by dextrose equivalent (DE), which is roughly the fraction of the glycosidic bonds in starch that have been broken.

These starch sugars are by far the most common starch based food ingredient and are used as sweeteners in many drinks and foods. They include:

  • Maltodextrin, a lightly hydrolyzed (DE 10–20) starch product used as a bland-tasting filler and thickener.
  • Various glucose syrups (DE 30–70), also called corn syrups in the US, viscous solutions used as sweeteners and thickeners in many kinds of processed foods.
  • Dextrose (DE 100), commercial glucose, prepared by the complete hydrolysis of starch.
  • High fructose syrup, made by treating dextrose solutions with the enzyme glucose isomerase, until a substantial fraction of the glucose has been converted to fructose. In the United States sugar prices are two to three times higher than in the rest of the world;[42] high-fructose corn syrup is significantly cheaper, and is the principal sweetener used in processed foods and beverages.[43] Fructose also has better microbiological stability. One kind of high fructose corn syrup, HFCS-55, is sweeter than sucrose because it is made with more fructose, while the sweetness of HFCS-42 is on par with sucrose.[44][45]
  • Sugar alcohols, such as maltitol, erythritol, sorbitol, mannitol and hydrogenated starch hydrolysate, are sweeteners made by reducing sugars.

Modified starches

A modified starch is a starch that has been chemically modified to allow the starch to function properly under conditions frequently encountered during processing or storage, such as high heat, high shear, low pH, freeze/thaw and cooling.

The modified food starches are E coded according to the International Numbering System for Food Additives (INS):[46]

  • 1400 Dextrin
  • 1401 Acid-treated starch
  • 1402 Alkaline-treated starch
  • 1403 Bleached starch
  • 1404 Oxidized starch
  • 1405 Starches, enzyme-treated
  • 1410 Monostarch phosphate
  • 1412 Distarch phosphate
  • 1413 Phosphated distarch phosphate
  • 1414 Acetylated distarch phosphate
  • 1420 Starch acetate
  • 1422 Acetylated distarch adipate
  • 1440 Hydroxypropyl starch
  • 1442 Hydroxypropyl distarch phosphate
  • 1443 Hydroxypropyl distarch glycerol
  • 1450 Starch sodium octenyl succinate
  • 1451 Acetylated oxidized starch

INS 1400, 1401, 1402, 1403 and 1405 are in the EU food ingredients without an E-number. Typical modified starches for technical applications are cationic starches, hydroxyethyl starch and carboxymethylated starches.

Use as food additive

As an additive for food processing, food starches are typically used as thickeners and stabilizers in foods such as puddings, custards, soups, sauces, gravies, pie fillings, and salad dressings, and to make noodles and pastas. Function as thickeners, extenders, emulsion stabilizers and are exceptional binders in processed meats.

Gummed sweets such as jelly beans and wine gums are not manufactured using a mold in the conventional sense. A tray is filled with native starch and leveled. A positive mold is then pressed into the starch leaving an impression of 1,000 or so jelly beans. The jelly mix is then poured into the impressions and put onto a stove to set. This method greatly reduces the number of molds that must be manufactured.

Use in pharmaceutical industry

In the pharmaceutical industry, starch is also used as an excipient, as tablet disintegrant, and as binder.

Resistant starch

Resistant starch is starch that escapes digestion in the small intestine of healthy individuals. High amylose starch from corn has a higher gelatinization temperature than other types of starch and retains its resistant starch content through baking, mild extrusion and other food processing techniques. It is used as an insoluble dietary fiber in processed foods such as bread, pasta, cookies, crackers, pretzels and other low moisture foods. It is also utilized as a dietary supplement for its health benefits. Published studies have shown that resistant starch helps to improve insulin sensitivity,[47] increases satiety[48] and improves markers of colonic function.[49] It has been suggested that resistant starch contributes to the health benefits of intact whole grains.[50]

Industrial applications

AdhesivesForHouseUse006
Starch adhesive

Papermaking

Papermaking is the largest non-food application for starches globally, consuming millions of metric tons annually.[12] In a typical sheet of copy paper for instance, the starch content may be as high as 8%. Both chemically modified and unmodified starches are used in papermaking. In the wet part of the papermaking process, generally called the "wet-end", the starches used are cationic and have a positive charge bound to the starch polymer. These starch derivatives associate with the anionic or negatively charged paper fibers / cellulose and inorganic fillers. Cationic starches together with other retention and internal sizing agents help to give the necessary strength properties to the paper web formed in the papermaking process (wet strength), and to provide strength to the final paper sheet (dry strength).

In the dry end of the papermaking process, the paper web is rewetted with a starch based solution. The process is called surface sizing. Starches used have been chemically, or enzymatically depolymerized at the paper mill or by the starch industry (oxidized starch). The size/starch solutions are applied to the paper web by means of various mechanical presses (size presses). Together with surface sizing agents the surface starches impart additional strength to the paper web and additionally provide water hold out or "size" for superior printing properties. Starch is also used in paper coatings as one of the binders for the coating formulations which include a mixture of pigments, binders and thickeners. Coated paper has improved smoothness, hardness, whiteness and gloss and thus improves printing characteristics.

Corrugated board adhesives

Corrugated board adhesives are the next largest application of non-food starches globally. Starch glues are mostly based on unmodified native starches, plus some additive such as borax and caustic soda. Part of the starch is gelatinized to carry the slurry of uncooked starches and prevent sedimentation. This opaque glue is called a SteinHall adhesive. The glue is applied on tips of the fluting. The fluted paper is pressed to paper called liner. This is then dried under high heat, which causes the rest of the uncooked starch in glue to swell/gelatinize. This gelatinizing makes the glue a fast and strong adhesive for corrugated board production.

Clothing starch

Clothing or laundry starch is a liquid prepared by mixing a vegetable starch in water (earlier preparations also had to be boiled), and is used in the laundering of clothes. Starch was widely used in Europe in the 16th and 17th centuries to stiffen the wide collars and ruffs of fine linen which surrounded the necks of the well-to-do. During the 19th and early 20th century it was stylish to stiffen the collars and sleeves of men's shirts and the ruffles of women's petticoats by applying starch to them as the clean clothes were being ironed. Starch gave clothing smooth, crisp edges, and had an additional practical purpose: dirt and sweat from a person's neck and wrists would stick to the starch rather than to the fibers of the clothing. The dirt would wash away along with the starch; after laundering, the starch would be reapplied. Today, starch is sold in aerosol cans for home use.

Other

Another large non-food starch application is in the construction industry, where starch is used in the gypsum wall board manufacturing process. Chemically modified or unmodified starches are added to the stucco containing primarily gypsum. Top and bottom heavyweight sheets of paper are applied to the formulation, and the process is allowed to heat and cure to form the eventual rigid wall board. The starches act as a glue for the cured gypsum rock with the paper covering, and also provide rigidity to the board.

Starch is used in the manufacture of various adhesives or glues[51] for book-binding, wallpaper adhesives, paper sack production, tube winding, gummed paper, envelope adhesives, school glues and bottle labeling. Starch derivatives, such as yellow dextrins, can be modified by addition of some chemicals to form a hard glue for paper work; some of those forms use borax or soda ash, which are mixed with the starch solution at 50–70 °C (122–158 °F) to create a very good adhesive. Sodium silicate can be added to reinforce these formula.

  • Textile chemicals from starch: warp sizing agents are used to reduce breaking of yarns during weaving. Starch is mainly used to size cotton based yarns. Modified starch is also used as textile printing thickener.
  • In oil exploration, starch is used to adjust the viscosity of drilling fluid, which is used to lubricate the drill head and suspend the grinding residue in petroleum extraction.
  • Starch is also used to make some packing peanuts, and some drop ceiling tiles.
  • In the printing industry, food grade starch[52] is used in the manufacture of anti-set-off spray powder used to separate printed sheets of paper to avoid wet ink being set off.
  • For body powder, powdered corn starch is used as a substitute for talcum powder, and similarly in other health and beauty products.
  • Starch is used to produce various bioplastics, synthetic polymers that are biodegradable. An example is polylactic acid based on glucose from starch.
  • Glucose from starch can be further fermented to biofuel corn ethanol using the so-called wet milling process. Today most bioethanol production plants use the dry milling process to ferment corn or other feedstock directly to ethanol.[53]
  • Hydrogen production could use glucose from starch as the raw material, using enzymes.[54]

Occupational safety and health

The Occupational Safety and Health Administration (OSHA) has set the legal limit (Permissible exposure limit) for starch exposure in the workplace as 15 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set a Recommended exposure limit (REL) of 10 mg/m3 total exposure and 5 mg/m3 respiratory exposure over an 8-hour workday.[55]

See also

References

  1. ^ Roy L. Whistler; James N. BeMiller; Eugene F. Paschall, eds. (2012). Starch: Chemistry and Technology. Academic Press. p. 220. Starch has variable density depending on botanical origin, prior treatment, and method of measurement
  2. ^ a b CRC Handbook of Chemistry and Physics, 49th edition, 1968-1969, p. D-188.
  3. ^ NIOSH Pocket Guide to Chemical Hazards. "#0567". National Institute for Occupational Safety and Health (NIOSH).
  4. ^ Brown, W. H.; Poon, T. (2005). Introduction to organic chemistry (3rd ed.). Wiley. ISBN 978-0-471-44451-0.
  5. ^ New Shorter Oxford Dictionary, Oxford, 1993
  6. ^ Revedin, A.; Aranguren, B.; Becattini, R.; Longo, L.; Marconi, E.; Lippi, M. M.; Skakun, N.; Sinitsyn, A.; et al. (2010). "Thirty thousand-year-old evidence of plant food processing". Proceedings of the National Academy of Sciences. 107 (44): 18815–9. doi:10.1073/pnas.1006993107. PMC 2973873. PMID 20956317.
  7. ^ "Porridge was eaten 100,000 years ago". The Telegraph. 18 Dec 2009.
  8. ^ Pliny the Elder, The Natural History (Pliny), Book XIII, Chapter 26, The paste used in preparation of paper
  9. ^ Pliny the Elder, The Natural History (Pliny), Book XIII, Chapter 17, [1]
  10. ^ Hunter, Dard (1947). Papermaking. DoverPublications. p. 194. ISBN 978-0-486-23619-3.
  11. ^ Starch Europe, AAF position on competitiveness, visited march 3 2019
  12. ^ a b NNFCC Renewable Chemicals Factsheet: Starch
  13. ^ International Starch Institute Denmark, Starch production volume
  14. ^ Starch Europe, Industry, visited march 3 2019
  15. ^ CRA, Industry overview 2017, visited on march 3 2019
  16. ^ Starch Europe, Updated position on the EU-US Transatlantic Trade and Investment Parnership, visited on march 3 2019
  17. ^ Vijn, Irma; Smeekens, Sjef (1999). "Fructan: more than a reserve carbohydrate?". Plant Physiology. 120 (2): 351–360. doi:10.1104/pp.120.2.351. PMC 1539216. PMID 10364386.
  18. ^ Zeeman, Samuel C.; Kossmann, Jens; Smith, Alison M. (June 2, 2010). "Starch: Its Metabolism, Evolution, and Biotechnological Modification in Plants". Annual Review of Plant Biology. 61 (1): 209–234. doi:10.1146/annurev-arplant-042809-112301. PMID 20192737.
  19. ^ Nelson, D. (2013) Lehninger Principles of Biochemistry, 6th ed., W.H. Freeman and Company (p. 819)
  20. ^ Smith, Alison M. (2001). "The Biosynthesis of Starch Granules". Biomacromolecules. 2 (2): 335–41. doi:10.1021/bm000133c. PMID 11749190.
  21. ^ Stryer, Lubert; Berg, Jeremy Mark; Tymoczko, John L. (2002). "Section 11.2.2". Biochemistry (5th ed.). San Francisco: W.H. Freeman. ISBN 978-0-7167-3051-4.
  22. ^ Ball, Steven G.; Matthew K Morell (2003). "FROM BACTERIAL GLYCOGEN TO STARCH: Understanding the Biogenesis of the Plant Starch Granule". Annual Review of Plant Biology. 54 (1): 207–233. doi:10.1146/annurev.arplant.54.031902.134927. PMID 14502990.
  23. ^ a b You, C.; Chen, H.; Myung, S.; Sathitsuksanoh, N.; Ma, H.; Zhang, X.-Z.; Li, J.; Zhang, Y.- H. P. (April 15, 2013). "Enzymatic transformation of nonfood biomass to starch". Proceedings of the National Academy of Sciences. 110 (18): 7182–7187. doi:10.1073/pnas.1302420110. PMC 3645547. PMID 23589840.
  24. ^ "Chemical Process Creates Food Source from Plant Waste". Voice of America. April 16, 2013. Retrieved January 27, 2017.
  25. ^ Zhang, Y.-H Percival (2013). "Next generation biorefineries will solve the food, biofuels, and environmental trilemma in the energy-food-water nexus". Energy Science. 1: 27–41. doi:10.1002/ese3.2.
  26. ^ Choi, Charles (April 15, 2013). "Could Wood Feed the World?". Science. Retrieved January 27, 2016.
  27. ^ Yu, TS; Kofler, H; Häusler, RE; et al. (August 2001). "The Arabidopsis sex1 mutant is defective in the R1 protein, a general regulator of starch degradation in plants, and not in the chloroplast hexose transporter" (PDF). Plant Cell. 13 (8): 1907–18. doi:10.1105/tpc.13.8.1907. PMC 139133. PMID 11487701.
  28. ^ a b Smith, Alison M.; Zeeman, Samuel C.; Smith, Steven M. (2005). "STARCH DEGRADATION" (PDF). Annual Review of Plant Biology. 56: 73–98. doi:10.1146/annurev.arplant.56.032604.144257. PMID 15862090.
  29. ^ Weise, SE; Weber, AP; Sharkey, TD (2004). "Maltose is the major form of carbon exported from the chloroplast at night". Planta. 218 (3): 474–82. doi:10.1007/s00425-003-1128-y. PMID 14566561.
  30. ^ Purdy, SJ; Bussell, JD; Nunn, CP; Smith, SM (2013). "Leaves of the Arabidopsis maltose exporter1 mutant exhibit a metabolic profile with features of cold acclimation in the warm". PLoS ONE. 8 (11): e79412. doi:10.1371/journal.pone.0079412. PMC 3818174. PMID 24223944.
  31. ^ Weber, A; Servaites, JC; Geiger, DR; et al. (May 2000). "Identification, purification, and molecular cloning of a putative plastidic glucose translocator". Plant Cell. 12 (5): 787–802. doi:10.1105/tpc.12.5.787. PMC 139927. PMID 10810150.
  32. ^ David R. Lineback, "Starch", in AccessScience@McGraw-Hill.
  33. ^ Perry, George H; Dominy, Nathaniel J; Claw, Katrina G; Lee, Arthur S; Fiegler, Heike; Redon, Richard; Werner, John; Villanea, Fernando A; et al. (2007). "Diet and the evolution of human amylase gene copy number variation". Nature Genetics. 39 (10): 1256–60. doi:10.1038/ng2123. PMC 2377015. PMID 17828263.
  34. ^ "Scope and Mechanism of Carbohydrase Action". The Journal of Biological Chemistry. 254.
  35. ^ Marc, A.; Engasser, J. M.; Moll, M.; Flayeux, R. (1983-02-01). "A kinetic model of starch hydrolysis by α- and β-amylase during mashing". Biotechnology and Bioengineering. 25 (2): 481–496. doi:10.1002/bit.260250214. ISSN 1097-0290. PMID 18548665.
  36. ^ Ph.D, Judit E. Puskas (2013-11-18). Introduction to Polymer Chemistry: A Biobased Approach. DEStech Publications, Inc. p. 138. ISBN 9781605950303.
  37. ^ Madhu, Sheri; Evans, Hayden A.; Doan-Nguyen, Vicky V. T.; Labram, John G.; Wu, Guang; Chabinyc, Michael L.; Seshadri, Ram; Wudl, Fred (4 July 2016). "Infinite Polyiodide Chains in the Pyrroloperylene-Iodine Complex: Insights into the Starch-Iodine and Perylene-Iodine Complexes". Angewandte Chemie International Edition. 55 (28): 8032–8035. doi:10.1002/anie.201601585. PMID 27239781.
  38. ^ Csepei, L. I.; Bolla, Cs. (2015). "IS STARCH ONLY A VISUAL INDICATOR FOR IODINE IN THE BRIGGS-RAUSCHER OSCILLATING REACTION?". STUDIA UNIVERSITATIS BABEŞ-BOLYAI Chemia (2): 187–199.
  39. ^ Anne-Charlotte Eliasson (2004). Starch in food: Structure, function and applications. Woodhead Publishing. ISBN 978-0-8493-2555-7.
  40. ^ Walter, Jens; Ley, Ruth (October 2011). "The Human Gut Microbiome: Ecology and Recent Evolutionary Changes". Annual Review of Microbiology. 65 (1): 422–429. doi:10.1146/annurev-micro-090110-102830. PMID 21682646.
  41. ^ Hemsley + Hemsley. "Arrowroot recipes". BBC Food. Retrieved 13 August 2017.
  42. ^ Forbes: HFCS Versus Sugar: A Modest Proposal for a Solution, 21 March 2012
  43. ^ Beverage daily: 'Sugar is much, much bigger': Rocketing HFCS prices don't spook Coke CEO
  44. ^ Ophardt, Charles. "Sweetners – Introduction". Elmhurst College.
  45. ^ White, John S. (December 2, 2008). "HFCS: How Sweet It Is".
  46. ^ Modified Starches. CODEX ALIMENTARIUS published in FNP 52 Add 9 (2001)
  47. ^ Maki, K. C.; Pelkman, C. L.; Finocchiaro, E. T.; Kelley, K. M.; Lawless, A. L.; Schild, A. L.; Rains, T. M. (2012). "Resistant Starch from High-Amylose Maize Increases Insulin Sensitivity in Overweight and Obese Men". Journal of Nutrition. 142 (4): 717–23. doi:10.3945/jn.111.152975. PMC 3301990. PMID 22357745.
  48. ^ Bodinham, Caroline L.; Frost, Gary S.; Robertson, M. Denise (2009). "Acute ingestion of resistant starch reduces food intake in healthy adults". British Journal of Nutrition. 103 (6): 917–22. doi:10.1017/S0007114509992534. PMID 19857367.
  49. ^ Nugent, A. P. (2005). "Health properties of resistant starch". Nutrition Bulletin. 30: 27–54. doi:10.1111/j.1467-3010.2005.00481.x.
  50. ^ Higgins, Janine A. (2012). "Whole Grains, Legumes, and the Subsequent Meal Effect: Implications for Blood Glucose Control and the Role of Fermentation". Journal of Nutrition and Metabolism. 2012: 1–7. doi:10.1155/2012/829238. PMC 3205742. PMID 22132324.
  51. ^ "Stuck on Starch: A new wood adhesive". US Department of Agriculture. 2000.
  52. ^ "Spray Powder". Russell-Webb. Archived from the original on 2007-08-09. Retrieved 2007-07-05.
  53. ^ American coalition for ethanol, Ethanol facilities
  54. ^ Zhang, Y.-H. Percival; Evans, Barbara R.; Mielenz, Jonathan R.; Hopkins, Robert C.; Adams, Michael W.W. (2007). Melis, Anastasios, ed. "High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic Pathway". PLoS ONE. 2 (5): e456. doi:10.1371/journal.pone.0000456. PMC 1866174. PMID 17520015.
  55. ^ "CDC – NIOSH Pocket Guide to Chemical Hazards – Starch". www.cdc.gov. Retrieved 2015-11-21.

External links

Amylase

Amylase () is an enzyme that catalyses the hydrolysis of starch into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion. Foods that contain large amounts of starch but little sugar, such as rice and potatoes, may acquire a slightly sweet taste as they are chewed because amylase degrades some of their starch into sugar. The pancreas and salivary gland make amylase (alpha amylase) to hydrolyse dietary starch into disaccharides and trisaccharides which are converted by other enzymes to glucose to supply the body with energy. Plants and some bacteria also produce amylase. As diastase, amylase is the first enzyme to be discovered and isolated (by Anselme Payen in 1833). Specific amylase proteins are designated by different Greek letters. All amylases are glycoside hydrolases and act on α-1,4-glycosidic bonds.

Amylose

Amylose is a polysaccharide made of α-D-glucose units, bonded to each other through α(1→4) glycosidic bonds. It is one of the two components of starch, making up approximately 20-30%. Amylose is more soluble in water than the other component amylopectin. Because of its tightly packed helical structure, amylose is more resistant to digestion than other starch molecules and is therefore an important form of resistant starch.

Associated British Foods

Associated British Foods plc (ABF) is a British multinational food processing and retailing company whose headquarters are in London. Its ingredients division is the world's second-largest producer of both sugar and baker's yeast and a major producer of other ingredients including emulsifiers, enzymes and lactose. Its grocery division is a major manufacturer of both branded and private label grocery products and includes the brands Mazola, Ovaltine, Ryvita, Jordans and Twinings. Its retail division, Primark, has around 345 stores with over 13,900,000 sq ft (1,290,000 m2) of selling space across Austria, Belgium, France, Germany, Italy, Ireland, the Netherlands, Portugal, Spain, the UK, and the United States.Associated British Foods is listed on the London Stock Exchange and is a constituent of the FTSE 100 Index.

Bioplastic

Bioplastics are plastics derived from renewable biomass sources, such as vegetable fats and oils, corn starch, straw, woodchips, food waste, etc. Bioplastic can be made from agricultural by-products and also from used plastic bottles and other containers using microorganisms. Common plastics, such as fossil-fuel plastics (also called petrobased polymers) are derived from petroleum or natural gas. Not all bioplastics are biodegradable nor biodegrade more readily than commodity fossil-fuel derived plastics. Bioplastics are usually derived from sugar derivatives, including starch, cellulose, and lactic acid. As of 2014, bioplastics represented approximately 0.2% of the global polymer market (300 million tons).

Carbohydrate

A carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula Cm(H2O)n (where m may be different from n). This formula holds true for monosaccharides. Some exceptions exist; for example, deoxyribose, a sugar component of DNA, has the empirical formula C5H10O4. The carbohydrates are technically hydrates of carbon; structurally it is more accurate to view them as aldoses and ketoses.

The term is most common in biochemistry, where it is a synonym of "saccharide", a group that includes sugars, starch, and cellulose. The saccharides are divided into four chemical groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides and disaccharides, the smallest (lower molecular weight) carbohydrates, are commonly referred to as sugars. The word saccharide comes from the Greek word σάκχαρον (sákkharon), meaning "sugar". While the scientific nomenclature of carbohydrates is complex, the names of the monosaccharides and disaccharides very often end in the suffix -ose, as in the monosaccharides fructose (fruit sugar) and glucose (starch sugar) and the disaccharides sucrose (cane or beet sugar) and lactose (milk sugar).

Carbohydrates perform numerous roles in living organisms. Polysaccharides serve for the storage of energy (e.g. starch and glycogen) and as structural components (e.g. cellulose in plants and chitin in arthropods). The 5-carbon monosaccharide ribose is an important component of coenzymes (e.g. ATP, FAD and NAD) and the backbone of the genetic molecule known as RNA. The related deoxyribose is a component of DNA. Saccharides and their derivatives include many other important biomolecules that play key roles in the immune system, fertilization, preventing pathogenesis, blood clotting, and development.They are found in a wide variety of natural and processed foods. Starch is a polysaccharide. It is abundant in cereals (wheat, maize, rice), potatoes, and processed food based on cereal flour, such as bread, pizza or pasta. Sugars appear in human diet mainly as table sugar (sucrose, extracted from sugarcane or sugar beets), lactose (abundant in milk), glucose and fructose, both of which occur naturally in honey, many fruits, and some vegetables. Table sugar, milk, or honey are often added to drinks and many prepared foods such as jam, biscuits and cakes.

Cellulose, a polysaccharide found in the cell walls of all plants, is one of the main components of insoluble dietary fiber. Although it is not digestible, insoluble dietary fiber helps to maintain a healthy digestive system by easing defecation. Other polysaccharides contained in dietary fiber include resistant starch and inulin, which feed some bacteria in the microbiota of the large intestine, and are metabolized by these bacteria to yield short-chain fatty acids.

Corn starch

Corn starch or maize starch is the starch derived from the corn (maize) grain. The starch is obtained from the endosperm of the kernel. Corn starch is a common food ingredient, used in thickening sauces or soups, and in making corn syrup and other sugars. It is versatile, easily modified, and finds many uses in industry as adhesives, in paper products, as an anti-sticking agent, and textile manufacturing. It has medical uses, such as to supply glucose for people with glycogen storage disease.Like many products in dust form, it can be hazardous in large quantities due to its flammability. When mixed with a fluid, cornstarch can rearrange itself into a non-Newtonian fluid. For example, adding water transforms cornstarch into a material commonly known as Oobleck while adding oil transforms cornstarch into an electrorheological (ER) fluid. The concept can be explained through the mixture termed "cornflour slime".

Corn syrup

Corn syrup is a food syrup which is made from the starch of corn (called maize in some countries) and contains varying amounts of maltose and higher oligosaccharides, depending on the grade. Corn syrup, also known as glucose syrup to confectioners, is used in foods to soften texture, add volume, prevent crystallization of sugar, and enhance flavor. Corn syrup is distinct from high-fructose corn syrup (HFCS), which is manufactured from corn syrup by converting a large proportion of its glucose into fructose using the enzyme D-xylose isomerase, thus producing a sweeter compound due to higher levels of fructose.

The more general term glucose syrup is often used synonymously with corn syrup, since glucose syrup in the United States is most commonly made from corn starch. Technically, glucose syrup is any liquid starch hydrolysate of mono-, di-, and higher-saccharides and can be made from any source of starch; wheat, tapioca and potatoes are the most common other sources.

Dextrin

Dextrins are a group of low-molecular-weight carbohydrates produced by the hydrolysis of starch or glycogen. Dextrins are mixtures of polymers of D-glucose units linked by α-(1→4) or α-(1→6) glycosidic bonds.

Dextrins can be produced from starch using enzymes like amylases, as during digestion in the human body and during malting and mashing, or by applying dry heat under acidic conditions (pyrolysis or roasting). The latter process is used industrially, and also occurs on the surface of bread during the baking process, contributing to flavor, color and crispness. Dextrins produced by heat are also known as pyrodextrins. The starch hydrolyses during roasting under acidic conditions, and short-chained starch parts partially rebranch with α-(1,6) bonds to the degraded starch molecule. See also Maillard Reaction.

Dextrins are white, yellow, or brown powder that are partially or fully water-soluble, yielding optically active solutions of low viscosity. Most of them can be detected with iodine solution, giving a red coloration; one distinguishes erythrodextrin (dextrin that colours red) and achrodextrin (giving no colour).

White and yellow dextrins from starch roasted with little or no acid are called British gum.

Dietary fiber

Dietary fiber or roughage is the portion of plant-derived food that cannot be completely broken down by digestive enzymes. It has two main components:

Soluble fiber – which dissolves in water – is readily fermented in the colon into gases and physiologically active by-products, such as short-chain fatty acids produced in the colon by gut bacteria; it is viscous, may be called prebiotic fiber, and delays gastric emptying which, in humans, can result in an extended feeling of fullness.

Insoluble fiber – which does not dissolve in water – is inert to digestive enzymes in the upper gastrointestinal tract and provides bulking. Some forms of insoluble fiber, such as resistant starches, can be fermented in the colon. Bulking fibers absorb water as they move through the digestive system, easing defecation.Dietary fiber consists of non-starch polysaccharides and other plant components such as cellulose, resistant starch, resistant dextrins, inulin, lignins, chitins, pectins, beta-glucans, and oligosaccharides.Dietary fibers can act by changing the nature of the contents of the gastrointestinal tract and by changing how other nutrients and chemicals are absorbed. Some types of soluble fiber absorb water to become a gelatinous, viscous substance which may or may not be fermented by bacteria in the digestive tract. Some types of insoluble fiber have bulking action and are not fermented. Lignin, a major dietary insoluble fiber source, may alter the rate and metabolism of soluble fibers. Other types of insoluble fiber, notably resistant starch, are fermented to produce short-chain fatty acids, which are physiologically active and confer health benefits. Health benefit from dietary fiber and whole grains may include a decreased risk of death and lower rates of coronary heart disease, colon cancer, and type 2 diabetes.Food sources of dietary fiber have traditionally been divided according to whether they provide soluble or insoluble fiber. Plant foods contain both types of fiber in varying amounts, according to the plant's characteristics of viscosity and fermentability. Advantages of consuming fiber depend upon which type of fiber is consumed and which benefits may result in the gastrointestinal system. Bulking fibers – such as cellulose, hemicellulose and psyllium – absorb and hold water, promoting regularity. Viscous fibers – such as beta-glucan and psyllium – thicken the fecal mass. Fermentable fibers – such as resistant starch and inulin – feed the bacteria and microbiota of the large intestine, and are metabolized to yield short-chain fatty acids, which have diverse roles in gastrointestinal health.

Glucose

Glucose (also called dextrose) is a simple sugar with the molecular formula C6H12O6. Glucose is the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight. There it is used to make cellulose in cell walls, which is the most abundant carbohydrate. In energy metabolism, glucose is the most important source of energy in all organisms. Glucose for metabolism is partially stored as a polymer, in plants mainly as starch and amylopectin and in animals as glycogen. Glucose circulates in the blood of animals as blood sugar. The naturally occurring form of glucose is D-glucose, while L-glucose is produced synthetically in comparably small amounts and is of lesser importance.

Glucose, as intravenous sugar solution, is on the World Health Organization's List of Essential Medicines, the most important medications needed in a basic health system. The name glucose derives through the French from the Greek γλυκός, which means "sweet," in reference to must, the sweet, first press of grapes in the making of wine. The suffix "-ose" is a chemical classifier, denoting a sugar.

Glucose syrup

Glucose syrup, also known as confectioner's glucose, is a syrup made from the hydrolysis of starch. Glucose is a sugar. Maize (corn) is commonly used as the source of the starch in the US, in which case the syrup is called "corn syrup", but glucose syrup is also made from potatoes and wheat, and less often from barley, rice and cassava.p. 21Glucose syrup containing over 90% glucose is used in industrial fermentation, but syrups used in confectionery contain varying amounts of glucose, maltose and higher oligosaccharides, depending on the grade, and can typically contain 10% to 43% glucose. Glucose syrup is used in foods to sweeten, soften texture and add volume. By converting some of the glucose in corn syrup into fructose (using an enzymatic process), a sweeter product, high fructose corn syrup can be produced.

It was first made in 1811 in Russia.

Glycogen

Glycogen is a multibranched polysaccharide of glucose that serves as a form of energy storage in animals, fungi, and bacteria. The polysaccharide structure represents the main storage form of glucose in the body.

Glycogen functions as one of two forms of long-term energy reserves, with the other form being triglyceride stores in adipose tissue (i.e., body fat). In humans, glycogen is made and stored primarily in the cells of the liver and skeletal muscle. In the liver, glycogen can make up from 5–6% of the organ's fresh weight and the liver of an adult weighing 70 kg can store roughly 100–120 grams of glycogen. In skeletal muscle, glycogen is found in a low concentration (1–2% of the muscle mass) and the skeletal muscle of an adult weighing 70 kg stores roughly 400 grams of glycogen. The amount of glycogen stored in the body—particularly within the muscles and liver—mostly depends on physical training, basal metabolic rate, and eating habits. Small amounts of glycogen are also found in other tissues and cells, including the kidneys, red blood cells, white blood cells, and glial cells in the brain. The uterus also stores glycogen during pregnancy to nourish the embryo.Approximately 4 grams of glucose are present in the blood of humans at all times; in fasted individuals, blood glucose is maintained constant at this level at the expense of glycogen stores in the liver and skeletal muscle. Glycogen stores in skeletal muscle serve as a form of energy storage for the muscle itself; however, the breakdown of muscle glycogen impedes muscle glucose uptake, thereby increasing the amount of blood glucose available for use in other tissues. Liver glycogen stores serve as a store of glucose for use throughout the body, particularly the central nervous system. The human brain consumes approximately 60% of blood glucose in fasted, sedentary individuals.Glycogen is the analogue of starch, a glucose polymer that functions as energy storage in plants. It has a structure similar to amylopectin (a component of starch), but is more extensively branched and compact than starch. Both are white powders in their dry state. Glycogen is found in the form of granules in the cytosol/cytoplasm in many cell types, and plays an important role in the glucose cycle. Glycogen forms an energy reserve that can be quickly mobilized to meet a sudden need for glucose, but one that is less compact than the energy reserves of triglycerides (lipids). As such it is also found as storage reserve in many parasitic protozoa.

Maltose

Maltose ( or ), also known as maltobiose or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) bond. In the isomer isomaltose, the two glucose molecules are joined with an α(1→6) bond. Maltose is the two-unit member of the amylose homologous series, the key structural motif of starch. When beta-amylase breaks down starch, it removes two glucose units at a time, producing maltose. An example of this reaction is found in germinating seeds, which is why it was named after malt. Unlike sucrose, it is a reducing sugar.

Mochi

Mochi (Japanese: 餅, もち) is Japanese rice cake made of mochigome, a short-grain japonica glutinous rice. The rice is pounded into paste and molded into the desired shape. In Japan it is traditionally made in a ceremony called mochitsuki. While also eaten year-round, mochi is a traditional food for the Japanese New Year and is commonly sold and eaten during that time.

Mochi is a multicomponent food consisting of polysaccharides, lipids, protein and water. Mochi has a heterogeneous structure of amylopectin gel, starch grains, and air bubbles. This rice is characterized by its low level of amylose starch, and is derived from short- or medium-grain japonica rices. The protein concentration of the rice is higher than that of normal short-grain rice, and the two also differ in amylose content. In mochi rice, the amylose content is negligible, and the amylopectin level is high, which results in its gel-like consistency.Mochi is similar to dango, but is made using pounded whole grains while dango are made of rice flour.

Polysaccharide

Polysaccharides () are polymeric carbohydrate molecules composed of long chains of monosaccharide units bound together by glycosidic linkages, and on hydrolysis give the constituent monosaccharides or oligosaccharides. They range in structure from linear to highly branched. Examples include storage polysaccharides such as starch and glycogen, and structural polysaccharides such as cellulose and chitin.

Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules can have distinct properties from their monosaccharide building blocks. They may be amorphous or even insoluble in water. When all the monosaccharides in a polysaccharide are the same type, the polysaccharide is called a homopolysaccharide or homoglycan, but when more than one type of monosaccharide is present they are called heteropolysaccharides or heteroglycans.Natural saccharides are generally of simple carbohydrates called monosaccharides with general formula (CH2O)n where n is three or more. Examples of monosaccharides are glucose, fructose, and glyceraldehyde. Polysaccharides, meanwhile, have a general formula of Cx(H2O)y where x is usually a large number between 200 and 2500. When the repeating units in the polymer backbone are six-carbon monosaccharides, as is often the case, the general formula simplifies to (C6H10O5)n, where typically 40≤n≤3000.

As a rule of thumb, polysaccharides contain more than ten monosaccharide units, whereas oligosaccharides contain three to ten monosaccharide units; but the precise cutoff varies somewhat according to convention. Polysaccharides are an important class of biological polymers. Their function in living organisms is usually either structure- or storage-related. Starch (a polymer of glucose) is used as a storage polysaccharide in plants, being found in the form of both amylose and the branched amylopectin. In animals, the structurally similar glucose polymer is the more densely branched glycogen, sometimes called "animal starch". Glycogen's properties allow it to be metabolized more quickly, which suits the active lives of moving animals.

Cellulose and chitin are examples of structural polysaccharides. Cellulose is used in the cell walls of plants and other organisms, and is said to be the most abundant organic molecule on Earth. It has many uses such as a significant role in the paper and textile industries, and is used as a feedstock for the production of rayon (via the viscose process), cellulose acetate, celluloid, and nitrocellulose. Chitin has a similar structure, but has nitrogen-containing side branches, increasing its strength. It is found in arthropod exoskeletons and in the cell walls of some fungi. It also has multiple uses, including surgical threads. Polysaccharides also include callose or laminarin, chrysolaminarin, xylan, arabinoxylan, mannan, fucoidan and galactomannan.

Potato starch

Potato starch is starch extracted from potatoes. The cells of the root tubers of the potato plant contain starch grains (leucoplasts). To extract the starch, the potatoes are crushed; the starch grains are released from the destroyed cells. The starch is then washed out and dried to powder.

Potato starch contains typical large oval spherical granules ranging in size between 5 and 100 μm. Potato starch is a very refined starch, containing minimal protein or fat. This gives the powder a clear white colour, and the cooked starch typical characteristics of neutral taste, good clarity, high binding strength, long texture and a minimal tendency to foaming or yellowing of the solution.

Potato starch contains approximately 800 ppm phosphate bound to the starch; this increases the viscosity and gives the solution a slightly anionic character, a low gelatinisation temperature of approximately 60 °C (140 °F), and high swelling power.

These typical properties are used in food and technical applications.

Sago

Sago is a starch extracted from the spongy centre, or pith, of various tropical palm stems, especially that of Metroxylon sagu. It is a major staple food for the lowland peoples of New Guinea and the Moluccas, where it is called saksak, rabia and sagu. The largest supply of sago comes from Southeast Asia, particularly Indonesia and Malaysia. Large quantities of sago are sent to Europe and North America for cooking purposes. It is traditionally cooked and eaten in various forms, such as rolled into balls, mixed with boiling water to form a glue-like paste (papeda), or as a pancake. Sago is often produced commercially in the form of "pearls" (small rounded starch aggregates, partly gelatinized by heating). Sago pearls can be boiled with water or milk and sugar to make a sweet sago pudding. Sago pearls are similar in appearance to the pearled starches of other origin, e.g. cassava starch (tapioca) and potato starch, and they may be used interchangeably in some dishes.

The name sago is also sometimes used for starch extracted from other sources, especially the sago cycad, Cycas revoluta. The sago cycad is also commonly known (confusingly) as the sago palm, although this is a misnomer as cycads are not palms. Extracting edible starch from the sago cycad requires special care due to the poisonous nature of cycads. Cycad sago is used for many of the same purposes as palm sago.

The fruit of palm trees from which the sago is produced is not allowed to ripen fully. The full ripening completes the life cycle of the tree and exhausts the starch reserves in the trunk to produce the seeds. It leaves a hollow shell and causes the tree to die. The palms are cut down when they are about 15 years old, just before or shortly after the inflorescence appears. The stems, which grow 10 to 15 metres high), are split out. The starch-containing pith is taken from the stems and ground to powder. The powder is kneaded in water over a cloth or sieve to release the starch. The water with the starch passes into a trough where the starch settles. After a few washings, the starch is ready to be used in cooking. A single palm yields about 800 pounds (360 kilograms) of dry starch.

Starch phosphorylase

Starch phosphorylase is a form of phosphorylase similar to glycogen phosphorylase, except that it acts upon starch instead of glycogen.

The plant alpha-glucan phosphorylase, commonly called starch phosphorylase (EC 2.4.1.1), is largely known for the phosphorolytic degradation of starch. Starch phosphorylase catalyzes the reversible transfer of glucosyl units from glucose-1-phosphate to the nonreducing end of alpha-1,4-D-glucan chains with the release of phosphate. Two distinct forms of starch phosphorylase, plastidic phosphorylase and cytosolic phosphorylase, have been consistently observed in higher plants.

Tapioca

Tapioca (; Portuguese: [tapiˈɔkɐ]) is a starch extracted from cassava plant (Manihot esculenta). This species is native to the north region and central-west region of Brazil, but its use spread throughout South America. The plant was carried by Portuguese and Spanish explorers to most of the West Indies and Africa and Asia. It is a tropical, perennial shrub that is less commonly cultivated in temperate climate zones. Cassava thrives better in poor soils than many other food plants.

Although tapioca is a staple food for millions of people in tropical countries, it provides only carbohydrate food value, and is low in protein, vitamins and minerals. In other countries, it is used as a thickening agent in various manufactured foods.

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