Choline chloride and amino acid solutions taste and hydration behavior with experimental thermodynamic properties and COSMO-PC-SAFT calculation

Abstract

Aqueous amino acid solutions have been introduced as dietary supplements for both animals and humans. This study investigates the physicochemical properties of the solutions containing amino acids (L-glycine, D,L-alanine, L-proline), choline chloride, and water at temperature range of 288.15 to 318.15 K. The results show that increasing concentrations of amino acids and choline chloride lead to higher solution densities. Analysis of apparent molar volume (V_φ) and apparent molar isentropic compressibility (κ_φ) reveals that V_φ values increase with choline chloride concentration and temperature, indicating enhanced solute-solvent interactions, while κ_φ values decrease, suggesting increased solution compression. Thermodynamic analysis using the Redlich-Mayer model and COSMO-based modeling provides insights into molecular interactions. However, COSMO-based parameters show high average relative deviation percentage (ARD %) values, indicating poor predictive performance for the density of these systems. In contrast, the ePC-SAFT equation of state effectively predicts the densities, particularly for L-proline-based solutions, which show very low ARD % values, indicating high accuracy. The ePC-SAFT model also performs reasonably well for L-glycine solutions but shows poorer results for D,L-alanine-based solutions. The study also examines the sweetness and saltiness criteria (ASV and ASIC) of these solutions. The ASV values, which serve as a sweetness criterion, are higher than the ideal range of 0.5 < ASV < 0.7, suggesting an overly sweet taste. The ASIC values follow a similar trend, indicating increased saltiness. To achieve an appropriate grade of sweetness and saltiness, dilution to lower concentrations of the solution is recommended. Furthermore, the use of choline chloride is found to increase salt intake and enhance the taste of salt, which can be beneficial in amino acid supplements used in animal food.

Keywords: Amino acid; COSMO; Choline chloride; PC-SAFT; Thermodynamic properties.

Figure 1

The apparent molar volume of choline chloride versus its molality in the presence of 0.05 mol kg⁻¹: (a) l-glycine, (b) l-alanine, and (c) l-proline at different temperatures.

Figure 2

(a) The σ-profiles of amino acids, choline chloride, and optimized structures of (b) l-glycine, (c) d,l-alanine, (d) l-proline, (e) choline chloride.