Physicochemical and psychophysical characteristics of binary mixtures of bulk and intense sweeteners

Correlating psychophysical characteristics with physicochemical properties of sweeteners is of relevance to the understanding of the origin of sweetener synergy, an essential parameter for the food manufacturer. Psychophysical evaluation was carried out on bulk sweeteners (sucrose and maltitol) and intense sweeteners (aspartame, sodium cyclamate, acesulfam-K, alitame) in mixtures. The concentrations of mixtures were calculated to be equisweet to 10% sucrose and sweetness intensity was evaluated by reference to sucrose solutions using a “sip and spit” method. While a positive synergistic phenomenon is observed for sugar/sodium cyclamate and maltitol/acesulfamK mixtures, a significant suppression effect is obtained when aspartame is added to sugars. Additivity is observed for sucrose/alitame and sucrose/acesulfamK mixtures. The origin of these differences lies in the influence of the two molecules on water structure and in the nature of their hydration. From physicochemical properties (intrinsic viscosity, Huggins coefficient, apparent specific volume, hydration number, surface tension and contact angle), alitame and aspartame seem characterised by hydrophobic hydration; sodium cyclamate, as well as the bulk sweeteners, appear more compatible with water structure and possess hydrophilic hydration. ACK is differentiated from other sweeteners by a negative hydration. Synergy occurs when components with identical types of hydration are mixed. This phenomenon is accompanied by an increase in the mobility of water molecules in the proximity of bulk sweeteners (maltitol and sucrose) and a reduction of volume of the hydrated solute molecule. Inversely, suppression and additivity occur when constituents of the mixture possess different natures of hydration, as in sucrose/aspartame mixtures, and when physicochemical properties show a reduction of the mobility of water around the sweeteners. For suppression effects, an increase in volume of the hydration sphere is also observed. Interpretation of the sweetness of mixtures of sugars and artificial sweeteners, in terms of their compatibility with water structure, is of relevance at an economic level in food formulations.