The effect of autoclaving on the dispersibility and stability of three neutral polysaccharides in dilute aqueous solutions

The dispersibility of three neutral polysaccharides, oat beta -glucan, deta rium xyloglucan and dextran in a dilute water-cadoxen mixture was studied b y viscosity measurement. It was found that intrinsic viscosity measurement, with water-cadoxen mixtures as solvents, is a useful tool to distinguish p olymer degradation from disruption of supramolecular aggregates. This appro ach, in conjunction with size exclusion chromatography, was used to study t he effects of heat and pressure treatment on the dispersibility and stabili ty of three polysaccharides in aqueous solutions. Autoclaving treatment at 121 degreesC for 15 min may reduce the degree of aggregation. Following aut oclaving in aqueous solution, the Huggins constants decreased from 0.66 to 0.42 for oat beta -glucan and from 0.63 to 0.56 for detarium xyloglucan. It remains the same for dextran, indicating good solubility of this polymer i n water. The current treatment did not cause evident changes in molecular w eight and structures to detarium xyloglucan and dextran. However, degradati on occurred with oat beta -glucan. The Burchard-Stockmayer-Fixman approach was applied to estimate the unperturbed dimension of oat beta -glucan and d etarium xyloglucan on samples after autoclaving. The characteristic ratio C -infinity was found to be 7.3 for detarium xyloglucan and 4.7 for oat beta -glucan, corresponding to the Kratky-Porod persistence lengths of 2.0 and 1 .2 nm, respectively. Crown Copyright (C) 2001 Published by Elsevier Science Ltd. All rights reserved.