Question

To determine the geletinization temperature range for given starch sample

Answer 1

Starch gelatinization is a process of breaking down the intermolecular bonds of starchmolecules in the presence of water and heat, allowing the hydrogen bonding sites (the hydroxyl hydrogen and oxygen) to engage more water. This irreversibly dissolves the starch granule in water. Water acts as aplasticizer. Three main processes happen to the starch granule: granule swelling, crystal or double helical melting, and amylose leaching.

During heating, water is first absorbed in the amorphous space of starch, which leads to a swelling phenomenon.[1]Water then enters via amorphous regions the tightly bound areas of double helicalstructures of amylopectin. At ambient temperatures these crystalline regions do not allow water to enter. Heat causes such regions to become diffuse, the amylose chains begin to dissolve, to separate into anamorphous form and the number and size of crystalline regions decreases. Under the microscope in polarized light starch loses its birefringence and its extinction cross. [2]Penetration of water thus increases the randomness in the starch granule structure, and causes swelling, eventually amylose molecules leach into the surrounding water and the granule structure disintegrates.