Polyoxyethylene alkyl and nonyl phenol ethers complexation with potato starch

Abstract

Starchy soil removal efficiency when cleaning food industry equipment can be affected by surfactant–starch complexes. Polyoxyethylene alkyl and nonyl phenol ethers complexation with potato starch has been studied by surface tension measurements. All surfactants assayed yield inclusion complexes with starch after a critical concentration of association was achieved. No starch saturation was observed throughout complexation until micellization, with bound surfactant being proportional to the total added surfactant. This bound/total surfactant ratio and the critical concentration of association seemed to depend mainly on the surfactant alkyl chain length. Unlike fatty alcohol ethoxylates, the nonyl phenol ethoxylate was feebly bound likely caused by its aromatic moiety. Binding isotherms and Scatchard plots suggested surfactants positive cooperative and non-cooperative binding with amylose and amylopectin respectively. Phosphate buffer raised surfactants binding capacity, ascribed either to an increase in cooperativity or to a reduction in the number of glucose units required to bind a surfactant molecule.