Water distribution in mixtures of soy protein isolates with starch and maltodextrin

Abstract

AbstractHydration of soy protein isolate and its mixtures with potato starch and starch hydrolyzate is studied by the pulsed nuclear magnetic resonance method. As the water content varies between 0.05 and 3 g per gram solid, the relaxation of magnetization of protons of studied systems is approximated by two exponents with the spin‐spin relaxation times falling within the ranges 2 to 10 ms and 20 to 200 ms. The values of relaxation times varying from 2 to 10 ms are attributed to the limited mobility of water molecules due to their interaction with the binding centers of macromolecules. Variations in the relaxation time from 20 to 200 ms with increasing water content is related to the limited mobility of water molecules as a result of two successive processes, namely filling and contraction of capillaries at low moisture content and formation of a fluctuation network of interactions between macromolecules at high water contents. The hydration of soy protein isolate‐starch mixtures is noted for a number of features. Water is found to redistribute in mixtures in a more hydrophilic component.