COMPLEXING BETWEEN STARCH AND POLY(ETHYLENE-CO-ACRYLIC ACID) - A COMPARISON OF STARCH VARIETIES AND COMPLEXING CONDITIONS

We have prepared starch-EAA complexes from different varieties of starch under a number of different reaction conditions. Water dispersions of starch at either 1 or 5% solid were combined with solutions of EAA in aqueous ammonia. Mixtures were air-dried, and the resulting composite films were then extracted with a solution of 1,1,2-trichloroethane, isopropanol, and toluene (15:15:70, by volume) to remove uncomplexed EAA. EAA content of composites after extraction was determined by FTIR. Because of its inability to form helical inclusion complexes with EAA, the microbial polysaccharide dextran was used to establish extraction conditions. Pretreatment of polysaccharide-EAA composites with methanol-water prior to extraction was essential for efficient removal of uncomplexed EAA. It was also necessary that methanol-water solutions be acidified to convert any residual ammonium carboxylate in the composite to carboxylic acid. The amount of FAA complexed by starch increased with an increase in the temperature used for gelatinization and also with the amylose content of the starch sample. Jet-cooked starch samples afforded the highest levels of complexation. Complex formation with cornstarch was not enhanced by the removal of amounts of lipid. Increased complexing of EAA was observed if composites were prepared at 1% as opposed to 5% solids. Under these conditions, complex formation with potato starch was about the same as that observed with cornstarch, indicating that phosphate substituents in potato starch do not influence complexing ability.