What is starch?
Starch is a polysaccharide comprised of D-glucose molecules. It is the most common, naturally occurring storage carbohydrate in plants. The starch is stored in the plant in the form of granules. The size of the granules depends on the origins of the starch and ranges from 1-2µm for amaranth and rice starch to roughly 100 µm for potato starch.
Both amylose and amylopectin develop during the synthesis of the D-glucopyranose polymer, which together form the starch granule. Amylose is a largely linear structured molecule made up of α-1.4 anhydroglucose units with an average molecular mass of 1x105-1x106 [g/mol]. Amylopectin is a branched molecule because, in contrast to amylose, it also has α-1.6 links besides the α-1.4. Amylopectin also has a higher molecular mass of 1x107-1x108 [g/mol].
In its native form, starch is insoluble in water and can only be irreversibly converted into a soluble form by heating it to a certain temperature, the gelatinisation temperature. It is only in its form as ‘pregelatinised starch’ that it develops the required properties such as rheology, water retention, glutinousness, etc. The starch paste can be converted into a dry, storable form by means of drum drying or spray drying, resulting in a product that is soluble in cold water.