Modification of starch properties with plasticizers

Starch is a homopolymer of glucopyranose units, but consists of two alpha-types of polymers: alpha(1,4)-linked, essentially linear amylose, and alpha(1,4)- and alpha(1,6)-linked amylopectin with a highly branched structure. In most applications, the semicrystalline, native starch granule structure is either destroyed or reorganized, or both. Water is the usual plasticizer in starch processing, and the physical properties of starch are greatly influenced by the amount of water present. Recently, the use of other plasticizers, such as low molecular weight alcohols, has received much attention, especially for the production of thermoplastic starches. This review discusses the influences of water and other plasticizers on the physical properties of starch. Recent developments for production of starch-based thermoplastics are described. These materials are expected to find increasing use in biodegradable plastics in a range of non-food uses.