Starch Gelatinization Information
Starch gelatinization is a process that breaks down the intermolecular bonds of starch molecules 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. Penetration of water increases randomness in the general granule structure and decreases the number and size of crystalline regions. Crystalline regions do not allow water entry. Heat causes such regions to become diffuse, so that the chains begin to separate into an amorphous form. Under the microscope in polarized light starch loses its birefringence and its extinction cross. This process is used in cooking to make roux sauce The gelatinization temperature of starch depends upon plant type and the amount of water present, pH, types and concentration of salt, sugar, fat and protein in the recipe, as well as derivatisation technology used. Some type of unmodified native starches start swelling at 55 °C, other types at 85 °C.[1] The gelatinization temperature depends on the degree of cross-linking of the amylopectin, and can be modified by genetic manipulation of starch synthase genes.[2]
Gelatinization temperature also depends on the amount of damaged starch granules. These will swell faster. Damaged starch can be produced, for example, during the wheat milling process, or when drying the starch cake in the starch plant.[3]
There is an inverse correlation between gelatinization temperature and glycemic index.[2]
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Retrogradation
Main article: Starch retrogradationCooked, unmodified starch, when cooled for a long enough period, will thicken( or gel) and rearrange itself again to a more crystalline structure; this process is called retrogradation.
Pregelatinized starch
Pregelatinized starch is starch cooked and then dried in the starch factory on a drum dryer or in an extruder making the starch cold water soluble.
See also
References
- ^ Hans-Dieter Belitz, Werner Grosch, Peter Schieberle, Food chemistry, Edition 3, Springer, page: 318-323, year: 2004, ISBN 3540408185, 9783540408185
- ^ a b US application 20080201807A1, Robert James Henry & Daniel Lex Ean Waters, "Gelatinization Temperature Manipulation", assigned to SOUTHERN CROSS UNIVERSITY, Rural Industries Research and Development Corporation
- ^ Stanley P. Cauvain, Linda S. Young, Baking problems solved, Woodhead Publishing, page: 25-26, year: 2001, ISBN 1855735644, 9781855735644
External links
- Food Resource, Starch, Oregon State University
- Corn starch gelatinization, filmed with microscope, Youtube
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