Starch is a complex carbohydrate which is insoluble in water. Starch (in particular cornstarch) is used in cooking for thickening sauces. In industry, it is used in the manufacture of adhesives, paper, and textiles.
In biochemistry, starch is a mix of two polymeric carbohydrates (polysaccharides) called amylose and amylopectin, in which the monomers are glucose units joined to one another head-to-tail. The overall structure of amylopectine is not, however, simply a linear polysaccharide chain, since occasionally, two glucose units are joined to one, forming a branch point.
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. 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 a practical purpose as well. Dirt and sweat from a man's neck and wrists would stick to the starch rather than fibers of the clothing, and would easily wash away along with the starch. Then, after each laundering, the starch would be reapplied.
Animal starch is the common name of glycogen. It is not the same as ordinary starch.
If you want to test if something has starch, such as plants, there's a simple way to do it. All you need is 2 jars, sugar, cornstarch, water, and some iodine. Your science teacher may have some iodine, so ask him/her.
Procedure: Fill both jars with about a cup of water. Then add a spoonful of cornstarch to one jar, and a spoonful of sugar to the other. Swish the jars until the sugar and cornstarch are well mixed in. Now add a few drops of iodine to each jar, and notice what happens. The iodine in the sugar water turned clear, but the iodine in the jar with cornstarch in it turned purple.
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