Starch, CAS# 9005-25-8,
chemical formula(C6H10O5)n is a polysaccharide carbohydrateconsisting of a large number of glucose monosaccharideunits joined together by glycosidic bonds. All plant seeds and tubers contain starch which is predominantly present as amyloseand amylopectin. Depending on the plant, starch generally contains 20 to 25 percent amylose and 75 to 80 percent amylopectin. Starch is also a carbohydrate that gives us energy. [Brown WH, Poon T (2005) Introduction to organic chemistry-Third edition, John Wiley & Sons (ISBN 0-471-44451-0)] .
Starch derived from
Middle English"sterchen", meaning to stiffen, which is appropriate since it can be used as a thickening agent when dissolved in water and heated. In several languages, starch is known as "sago" or "sagu"; consequently, in English sagonow refers to several different starches (see Sago (disambiguation)). Starch is basically long chains of glucose molecules.
ources of starch
Starch is a white powder, and depending on the source, may be
tasteless and odorless. Microscopically, starch grains are fine crystals or lumps; the precise form of these grains varies within the plant kingdom. Today, commercial starches include cornstarch, arrowroot, potato starch, sagoand tapioca. Historically they included Florida arrowroot.
Starch in its basic refined form is used in cooking to thicken foods such as sauces. In industry, it is used in the manufacturing of
adhesives, paper, textiles and as a mold in the manufacture of sweets such as wine gumsand jelly beans. It is also used in the form of flakes, sticks, and pearls (tapioca and sago).
Starch is by far the most consumed polysaccharide in the human diet. Traditional staple foods such as
cereals, roots and tubersare the main source of dietary starch.
The technical term for a colorless, tasteless, odorless, and "edible" starch is a fecula.
Starch is often found in the
fruit, seeds, rhizomes or tubers of plants and is the major source of energy in these food items. The major resources for starch production and consumption worldwide are rice, wheat, corn, and potatoes. Fresh chestnut has twice as much starch as potato. As the chestnut ripens, some of its starch is gradually converted into sugars. [http://www.buychestnuts.com/trees.htm Delmarvelous nursery] (Chestnut Trees & Seed Nuts).] Cooked foods containing starches include boiled rice, various forms of breadand noodles(including pasta).
additivefor food processing, arrowrootand tapiocaare commonly used as well. Commonly used starches around the world are: arracacha, buckwheat, banana, barley, cassava, kudzu, oca, sago, sorghum, regular household potatos, sweet potato, taroand yams. Edible beans, such as favas, lentilsand peas, are also rich in starch.
When a starch is pre-cooked, it can then be used to thicken cold foods. This is referred to as a pregelatinized starch. Otherwise starch requires heat to thicken, or "gelatinize." Vague|date=March 2008The actual temperature depends on the type of starch.
A modified food starch undergoes one or more chemical modifications, which allow it to function properly under high heat and/or shear frequently encountered during 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, but have many other uses.
The modified starches are coded according to the International Numbering System for Food Additives (INS) :
1401 Acid-treated starch
1402 Alkaline treated starch
1403 Bleached starch
1404 Oxidized starch
1405 Starches, enzyme-treated
1410 Monostarch phosphate
1411 Distarch glycerol
1412 Distarch phosphate esterified with sodium trimetaphosphate
1413 Phosphated distarch phosphate
1414 Acetylated distarch phosphate
1420 Starch acetate esterified with acetic anhydride
1421 Starch acetate esterified with vinyl acetate
1422 Acetylated distarch adipate
1423 Acetylated distarch glycerol
1440 Hydroxypropyl starch
1442 Hydroxypropyl distarch phosphate
1443 Hydroxypropyl distarch glycerol
1450 Starch sodium octenyl succinate
Resistant starchis starch that escapes digestion in the small intestine of healthy individuals. Plants use starch as a way to store excess glucose, and thus also use starch as food during mitochondrial oxidative phosphorylation.
Papermakingis the largest non-food application for starches globally, consuming millions of metric tons annually. 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”, starches are chemically modified to contain a cationic or positive charge bound to the starch polymer, and are utilized to associate with the anionic or negatively charged paper fibers and inorganic fillers.
These cationic starches impart the necessary strength properties for the paper web to be 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 solution of starch paste that has been chemically, or enzymatically depolymerized. The starch paste solutions are applied to the paper web by means of various mechanical presses (size press). The dry end starches impart additional strength to the paper web and additionally provide water hold out or “size” for superior printing properties.
Corrugating glues are the next largest consumer of non-food starches globally. These
glues are used in the production of corrugated fiberboard(sometimes called corrugated cardboard), and generally contain a mixture of chemically modified and unmodified starches that have been partially gelatinized to form an opaque paste. This paste is applied to the flute tips of the interior fluted paper to glue the fluted paper to the outside paper in the construction of cardboard boxes. This is then dried under high heat, which provides the box board strength and rigidity.
Another large non-food starch application is in the construction industry where starch is used in the gypsum
wall boardmanufacturing 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.
Clothing starch or laundry starch is a liquid that is 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
Europein 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 century and early 20th century, it was stylish to stiffen the collars and sleeves of men's shirts and the ruffles of girls' petticoats by applying starch to them as the clean clothes were being ironed. Aside from the smooth, crisp edges it gave to clothing, it served practical purposes as well. Dirt and sweatfrom a person's neck and wrists would stick to the starch rather than fibers of the clothing, and would easily wash away along with the starch. After each laundering, the starch would be reapplied. Today the product is sold in aerosol cans for home use.
Starch is also used to make some
packing peanuts, and some dropped ceilingtiles.
Printing industry - in the
printingindustry food grade starch [Cite web | url = http://www.russell-webb.com/anti_set_off_powder/soluble_anti-set-off-powder.html
title = Spray Powder
publisher = - Russell-Webb
accessdate = 2007-07-05] is used in the manufacture of
anti-set-off spray powderused to separate printed sheets of paper to avoid wet ink being set off. Starch is also used in the manufacture of glues [Cite web | url = http://www.nationalstarch.com/NationalStarch/About+Us/Our+Businesses
title = Starch based glue
publisher = - ICI] for book-binding.
Hydrogen production - Starch can be used to produce
Hydrogen. [Cite web | url = http://www.plosone.org/article/fetchArticle.action?articleURI=info:doi/10.1371/journal.pone.0000456
title = High-Yield Hydrogen Production from Starch and Water by a Synthetic Enzymatic Pathway
accessdate = 2007-07-15]
Oil exploration - starch is used as to adjust the viscosity of
drilling fluidwhich is used to lubricate the drill head in (mineral) oil extraction.
Body powder - Powdered corn starch is used as a substitute for
talcumpowder in many health and beauty products.
Use as a mold
Gummed sweets such as
jelly beansand wine gumsare not manufactured using a mold in the conventional sense. A tray is filled with starch and leveled. A positive mold is then pressed into the starch leaving an impression of 1000 or so jelly beans. The mix is then poured into the impressions and then put into a stove to set. This method greatly reduces the number of molds that must be manufactured.
Starch can be modified by addition of some chemical forms to be a hard glue for paper work , some of those forms are Borax , Soda Ash , which mixed with the starch solution at 50-70C to gain a very good adhesive, Sodium Silicate can be added to reinforce this formula.
Iodinesolution is used to test for starch. A bluish-black color indicates the presence of iodine in the starch solution. It is thought that the iodine fits inside the coils of amylose. [http://www.bhsu.edu/Portals/0/coartssciences/science/Chemistry/Chemistry107/chem107Lmanual2004.pdf] A 0.3% w/wsolution is the standard concentration for a dilute starch indicatorsolution. It is made by adding 4 grams of soluble starch to 1 litre of heated water; the solution is cooled before use (starch-iodine complex becomes unstable at temperatures above 35 °C). This complex is often used in redoxtitrations: in presence of an oxidizing agentthe 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 complex.
microscope, starch grains illuminated from behind with polarized lightshow a distinctive Maltese crosseffect (also known as extinction crossand birefringence).
Starch can be
hydrolyzedinto simpler carbohydrates by acids, various enzymes, or a combination of the two. The extent of conversion is typically quantified by "dextrose equivalency" (DE), which is roughly the fraction of the glycoside bonds in starch that have been broken. Food products made in this way include:
Maltodextrin, a lightly hydrolyzed (DE 10–20) starch product used as a bland-tasting filler and thickener.
corn syrups (DE 30–70), 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, high fructose corn syrupis the principal sweetener used in sweetened beverages because fructose tastes sweeter than glucose, and less sweetener may be used.
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