Hydration properties and the role of water in taste modalities of sucrose,caffeine, and sucrose-caffeine mixtures

Solution properties of sapid molecules are informative on their type of hyd ration (hydrophobic or hydrophilic) and on the extent of the hydration laye r. Physicochemical properties (intrinsic viscosity and apparent specific vo lume) and nuclear magnetic resonance (NMR) relaxation rates R-1 and R-2 for pure sucrose, bitter molecule caffeine, and their mixture were found to be relevant in the interpretation of the effects of these solutes on water mo bility. Likewise, surface tension, contact angles with a hydrophobic surfac e, and the adhesion forces to this type of surface of the aqueous solutions of sapid molecules were found to discriminate between their effects on wat er cohesion and also between their taste qualities. The interpretation of t he two sets of independent experimental results, namely physicochemical and spectroscopic data, helps in the elucidation of the role of water in sweet and bitter taste chemoreception.