Study of volumetric properties of binary aqueous solutions of selected natural and artificial sweeteners at various temperatures

Abstract

This work presents investigations of the density, sound velocity, volumetric and acoustical behavior of binary aqueous solutions of some sweeteners namely acesulfame potassium, sodium cyclamate, sodium saccharin; D-mannitol, maltose, and poly sucralose at 293.15–318.15 K. The entire work was done at atmospheric pressure. The objective of study was to support building a suitable relationship among densities, sound velocities, sweeteners’ concentration and structural characteristics to explore sweetness response and molecular interactions in aqueous solution. Densities () and sound velocities (μ) have been measured as a function of concentration for aqueous solutions at 293.15–318.15 K and atmospheric pressure using electronic vibrating U tube density and sound velocity meter (DSA 5000M). Solutions of acesulfame- K, cyclamate- Na and saccharin- Na were treated as electrolytes, while D- mannitol, maltose and poly sucralose were considered as non-electrolytes. The results obtained were used to compute their apparent and partial Molal volumes; isentropic apparent and partial Molal isentropic compressibilities and compressibility hydration numbers have been calculated and reported. The apparent Molal volume, (ΦV) of electrolytes indicates negative deviations from Debye-Huckel limiting law. The values obtained for, ΦV, at given temperatures and concentrations may be used as an indicative for the strength and intensity of the ion/solute–ion/solute and ion/solute-solvent interactions. The partial Molal volume (ΦV°) indicates hydrophilic interactions dominating in aqueous solutions of studied sweeteners. Furthermore, apparent specific volumes (ASV) of the ions/solutes were calculated and it was found that these values of the investigated solutes lie between the reported values for sweet substances (0.51 – 0.71 cm3g-1) except for poly sucralose which might behaves differently due to its long chain structure. The partial Molal expansibility (ΦE°), Hepler’s constant (∂2V0/∂T2) and thermal expansion coefficient (a°) have been estimated and correlated to the effect of temperature on solution behavior. The isentropic apparent Molal compressibility (ΦK(s)) and compressibility hydration number (nH) conferred pre-dominance of ion/solute-solvent interactions, whereas partial Molal expansibility and related standards predicted structure making or breaking behavior of studied sweeteners. The Hepler’s constant values for sodium cyclamate and maltose x were negative which associated with the water structure breaking behavior of these sweeteners. The thermodynamic parameters like Apparent Molal volume (ΦV), partial Molal volume (ΦV°), apparent specific volume (ASV), partial Molal expansibility (ΦE°), isentropic apparent Molal compressibility (ΦK(s)) and related constants provided clear distinctions and variable hydration behavior and sweetness response from class to class, structural variability and molecular masses. So, as a whole this study provided new insights in elucidation of mechanistic differences between sweeteners and their mode of interactions.