Starch is commonly known as doughnut flour.

Starch is a polymer carbohydrate, a polysaccharide formed by the polymerization of glucose molecules. Its basic building block is α-D-glucopyranose, with the molecular formula (C6H10O5)n.

There are two types of starch: straight-chain starch and branched-chain starch. The former has an unbranched helical structure; the latter has 24~30 glucose residues linked head to tail by α-1,4-glycosidic bonds, with α-1,6-glycosidic bonds at the branched chains.

Physical properties

1, adsorption properties

Starch can adsorb many organic compounds and inorganic compounds, straight-chain starch and branched-chain starch due to the different molecular morphology has different adsorption properties. Straight-chain starch molecules in solution have good molecular stretching, and it is easy to be bonded with some polar organic compounds such as n-butanol, fatty acids, etc. through hydrogen bonding, forming a crystalline complex and precipitation.

2, solubility

The solubility of starch refers to the dissolved mass fraction of starch sample molecules after heating in water for 30min at a certain temperature. Starch granules are insoluble in cold water, damaged starch or chemically modified starch can be dissolved in cold water, but the dissolved moistened starch is not reversible. As the temperature rises, the swelling of the starch increases and the solubility increases.