State diagrams of arabinoxylan-water binaries

Since Arabinoxylans are natural polysaccharides that seem promising candida tes as cryostabilizers, the state diagram (i.e. the representation in the t emperature-composition plan of the macroscopic phases) of their aqueous sol utions seemed worth determining. Two lots of purified water extractable arabinoxylans (WEA) of different mol ecular mass (56 and 410 kDa labeled as LMW-AX and HMW-AX respectively) were used to prepare aqueous solutions of various composition. These were coole d below their freezing point and annealed for 2 h at a suitable temperature before a DSC 5 degreesC min(-1) heating run aimed at determining their pri mary glass transition temperature, T-g', and the onset of ice fusion. Once the corresponding composition, C-g' was assessed, the main curves of the co rresponding state diagram were drawn. As expected, the T-g' value drawn for HMW-AX was higher (-17 degreesC) than for LMW-AX (-35 degreesC). The C-g' was instead found close to 75% w/w for both HMW-AX and LMW-AX. The fictitiousness of this coincidence could be ea sily recognized by expressing the solute concentration in molar fraction, X : it was then possible to verify that, as expected, X-g' for LMW-AX was one order of magnitude larger than for HLW-AX. (C) 2001 Elsevier Science B.V. All rights reserved.