Volumetric, acoustic, viscometric, calorimetric and spectroscopic studies to elucidate the effects of citrate and tartrate based food preservatives on the solvation behaviors of acidic amino acids at different temperatures.

The effects of trisodium citrate (TSC) and disodium tartrate (DST) based food preservatives on the hydration behaviors of the amino acids l-aspartic acid (ASP) and l-glutamic acid (GLU) have been studied using thermodynamic, transport, calorimetric and spectroscopic studies. The volumetric, acoustic and viscosity data suggest that hydrophilic-ionic/hydrophilic interactions are predominant in these systems. The calculated parameters are worthwhile for exploring the solutes as structure-breakers, and the solutes undergo pairwise interactions with the co-solutes. The sweetness of both amino acids decreases in the presence of the preservatives. The hydration number and solvation data suggest that these solutes are more hydrated in water. The dominance of dehydration effects in relation to TSC is observed from the positive enthalpy changes in calorimetry studies and the negative chemical shifts in 1H NMR studies.

Effect of potassium chloride on the solvation behavior of caffeine, theophylline and theobromine: Volumetric, viscometric, calorimetry and spectroscopic approach.

The density (ρ), speed of sound (u), viscosity (η) and enthalpy of dilution (q) measurements for methylxanthines (caffeine, theophylline and theobromine) in aqueous medium and in aqueous solutions of (0.10-1.00) mol·kg-1 KCl covering a temperature range T = (288.15-318.15) K and at p = 101.325 kPa have been accomplished using a density and sound velocity meter, Micro-Ubbelohde type capillary viscometer and Isothermal Titration Calorimetry, respectively. Transfer parameters evaluated from the data suggest that competition among various interactions exists at low and high molalities of KCl(aq.) solutions. The increase in bitterness and decrease in hydration number of methylxanthines with the mB values have been observed. The dehydration effect of KCl(aq.) at low molalities on the methylxanthines has also been established using ITC. Positive change in the chemical shifts (1H NMR) and increase in absorption intensity (UV-vis) of methylxanthines in the presence of KCl(aq.) further support our results.