PHYSICOCHEMICAL PROPERTIES AND VIBRATIONAL-SPECTRA OF SMALL CARBOHYDRATES IN AQUEOUS-SOLUTION AND THE ROLE OF WATER IN THEIR SWEET TASTE

Solution properties (intrinsic viscosity, apparent specific volume, hy dration number and surface tension) were determined for three nutritiv e sugars (D-glucose, D-fructose and sucrose) and three polyols (xylito l, sorbitol and lactitol) in water and in 1% (w/w) aqueous salt (NaCl, KCl or MgCl2) solution. Likewise, the laser-Raman spectra of these ca rbohydrates in water (10% (w/w)) or in salt solutions were recorded in the OH stretching region (3800-2800 cm(-1)) and analysed by compariso n to the Raman band of water fitted to 4 Gaussian components. Microwav e spectra of saturated sugar solutions were also obtained and interpre ted in terms of polarity of the sugars. Comparison of the physicochemi cal results and Raman data in water, on the one hand, and in salt solu tion on the other, permitted determination of the influence of the bio logically important cations (Na+, K+ and Mg2+) on the effect of sugars and polyols on water structure. This is also useful to support our th ree-step model of sweet taste chemoreception which relies on the fact that water mobility and the polarity of stimulant are the clue to the elucidation of the sweetness mechanism. Copyright (C) 1996 Elsevier Sc ience Ltd