Starch chemical formula is (C6H10O5)n, belongs to the polymerized carbohydrates consisting of a large number of glucose units connected by glycosidic bonds, and belongs to a kind of polysaccharide.
Pure starch is a white, tasteless, odorless powder, insoluble in cold water or alcohol. Starch can be divided into straight-chain starch (saccharine starch) and branched-chain starch (gum starch) due to the difference in the structure of the intra-molecular hydrogen bonds curled into a helix.
The former is a spiral structure without branching; the latter is made of 24~30 glucose residues connected by α-1,4-glycosidic bonds, and α-1,6-glycosidic bonds at the branched chain. Straight-chain starch is blue when exposed to iodine, and branched-chain starch is purplish red when exposed to iodine.
This is due to the central cavity of the starch helix can accommodate the iodine molecule, due to van der Waals force, the two form a blue-black complex. Experiments have shown that iodine molecules alone cannot turn starch blue, and it is actually the triiodide anion that turns starch blue.
Starch is processed in the food industry to produce a variety of sugars. Starch is dissolved in warm water to produce dextrin, which can be used as a thickener, and hardened to act as a bonding agent. The most widespread use of starch in the non-food industry is as a binder in the papermaking process.
Extended information
History
It has been established that cattail (cattails, bullrushes) rhizome starch was present in 30,000-year-old stone-ground flour grains found in Europe. Records of possible extraction of pure wheat starch paste have also been found in ancient Egyptian papyrus gum. According to Pliny the Elder's Natural History, starch was first extracted in 77-79 AD. The Romans also used starch in beauty creams to dust their hair.
The Persians and Indians used it in cooking to thicken sauces. Since as early as 700 AD, the Chinese have been producing paper with a surface treatment of rice starch. By 2008, 66 million tons of non-directly edible starch were produced worldwide. In the European Union about 8.5 million tons, about 40% are used in industrial applications and 60% in food applications, the latter being high fructose corn syrup.
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