Chemically Modified Starch; Allyl- and Epoxy-Starch Derivatives: Their Synthesis and Characterization

Both native and modified starches, such as starch that is pregelatinized, extruded, acid-converted, cross-linked, and substituted, are widely used in industry. This chapter describes a mild two-step process for the synthesis of novel, highly reactive granular epoxy-starch derivatives. Via this method, granular maize starch was substituted with allyl glycidyl ether (AGE) followed by epoxidation of the double bond. Alkali-mediated etherification of maize starch with AGE produced unsaturated starch derivatives with a degree of substitution of 0.2. NMR analysis showed that the glucose moiety of the starch is mainly substituted at the O-6 position. At polymer level, the allyl groups are clustered and randomly distributed along the polymer chain, depending on the type of starch. Incorporation of AGE affected the physical and rheological properties of maize starches. By epoxidation of the double bonds of AGE, starch derivatives carrying epoxy and hydroxyl groups, as well as intra- and intermolecular cross-links, were formed.