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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]
Iodine–starch test. A bottle of iodine solution used on apples to determine the correct harvest time. The chart shows the level of residual starch. The cut surface of an apple stained with iodine, indicating a starch level of 4–5. The iodine–starch test is a chemical reaction that is used to test for the presence of starch or for iodine.
As water is heated with starch granules, gelatinization occurs, involving an endothermic reaction. [8] The initiation of gelatinization is called the T-onset. T-peak is the position where the endothermic reaction occurs at the maximum. T-conclusion is when all the starch granules are fully gelatinized and the curve remains stable.
Retrogradation is a reaction that takes place when the amylose and amylopectin chains in cooked, gelatinized starch realign themselves as the cooked starch cools. [1]When native starch is heated and dissolved in water, the crystalline structure of amylose and amylopectin molecules is lost and they hydrate to form a viscous solution.
The iodine clock reaction is a classical chemical clock demonstration experiment to display chemical kinetics in action; it was discovered by Hans Heinrich Landolt in 1886. [1] The iodine clock reaction exists in several variations, which each involve iodine species ( iodide ion, free iodine, or iodate ion) and redox reagents in the presence of ...
proteins. An amylase (/ ˈæmɪleɪs /) is an enzyme that catalyses the hydrolysis of starch (Latin amylum) into sugars. Amylase is present in the saliva of humans and some other mammals, where it begins the chemical process of digestion.
In enzymology, a starch synthase ( EC 2.4.1.21) is an enzyme that catalyzes the chemical reaction. Thus, the two substrates of this enzyme are ADP-glucose and a chain of D- glucose residues joined by 1,4-alpha- glycosidic bonds, whereas its two products are ADP and an elongated chain of glucose residues.
α-Amylase is an enzyme (EC 3.2.1.1; systematic name 4-α-D-glucan glucanohydrolase) that hydrolyses α bonds of large, α-linked polysaccharides, such as starch and glycogen, yielding shorter chains thereof, dextrins, and maltose, through the following biochemical process: [2] It is the major form of amylase found in humans and other mammals. [3]