Starch gelatinization is a process that occurs when starch granules are heated in the presence of water, causing the granules to swell and absorb water irreversibly, resulting in a viscous and transparent texture. The process involves breaking down the intermolecular bonds of starch molecules, allowing the hydrogen bonding sites to engage more water. The following are the three main processes that happen to the starch granule during gelatinization:
- Granule swelling: During heating, water is first absorbed in the amorphous space of starch, which leads to a swelling phenomenon.
- Crystallite and double-helical melting: The crystalline regions of the starch granule melt, and the double helices of amylose and amylopectin are disrupted.
- Amylose leaching: Amylose molecules are released from the granule and dissolve in the surrounding water.
Gelatinization improves the availability of starch for amylase hydrolysis, making it digestible. Gelatinized starch is used in cooking to thicken or bind water in roux, sauce, or soup. Retrogradation is a process that occurs when gelatinized starch is cooled for a long enough period, causing it to thicken or gel and rearrange itself to a more crystalline structure. The extent of starch gelatinization varies with temperature, heating rate and extent of heating, available water, pH, and type of starch.
