APPARENT MOLAR VOLUMES AND H-1-NMR RELAXATION VALUES OF GLUCOSE SYRUPS

The apparent molar volumes and proton magnetic resonance H-1-NMR pulse relaxation values Of D-glucose and four commercial glucose syrups were determined in the concentration range 5-50 % (w/w). The apparent molar volumes increased linearly with average degree of polymerisation (DP) of the syrups and were thus in excellent agreement with average molecular weight. These increases contrasted markedly with the known increases of specific rotation of maltooligosaccharides which reach a limiting value at about DP 7 or 8. Apparent specific volumes were all confined to the range 0.60-0.64 cm3g-1 as expected for carbohydrates. They decreased sharply in the DP range 1-3 and showed little change thereafter. Apparent specific volumes also increased with increasing concentration of solute, as expected. Spin-spin relaxation values (T2-values) decreased with increasing DP or increasing concentration of solute, as the proportion of ordered protons in solution increased. Consequently, within one glucose syrup, T2 decreased with increasing apparent specific volume (increasing concentration) and, between glucose syrups, T2 decreased with increasing DP. These results reflect the packing characteristics of the solutes among water molecules and accord with their known sweetness properties. They also underline the value of solution properties for the rapid characterisation of glucose syrups.