Starch Properties, Modifications, and Applications

Starch is the second largest biomass produced on earth. Starch consists mainly of amylose and amylopectin. The chemical structures of starch molecules, polymers of α-1-4 linked glucopyranose with α-1-6 branches, render a natural tendency for starch in aqueous systems to crystallize to double helices. Depending on botanical origin and genetic background, starch has different chemical structures, such as branchchain lengths and phosphate derivatives, and different functional properties. This structural and functional diversity makes these starches suitable for different applications. High-amylose starch produces strong films and is suitable for making biodegradable plastics, and smallgranule starch is an appropriate polyethylene film filler. Various physical, chemical, and enzymatic modifications will change and improve functional properties of starch and facilitate its utilization for different purposes. Pregelatinized and cold-water-soluble starches enable users to disperse starch without going through a heating process. Hydrophobic starch derivatives enhance the compatibility between starch and hydrophobic components. Dialdehyde starch facilitates crosslinkages between starch and other components carrying functional groups, such as amino, hydroxyl, and sulfurhydryl groups.