Modeling the solid-liquid equilibrium of binary mixtures of triacylglycerols using UNIFAC and predictive UNIQUAC models

The modeling of solid-liquid equilibrium is often performed assuming a series of theoretical simplifications, such as the compounds’ immiscibility in the solid phase. Unfortunately, this is not true for several systems, including food compounds. For example, triacylglycerol (TAG) molecules are the main components of fats and oils. Because of their characteristic solid transition phenomena such as polymorphism and solid solution formation, the quality of oil- and fat-based products is essentially dependent on TAG mixtures’ phase behavior. This work aimed to evaluate the use of a predictive approach based on UNIFAC and a predictive version of UNIQUAC to describe the solid-liquid equilibrium (SLE) behavior of binary mixtures containing TAG species. We put forth a validation test for the modeling approach, using experimental data of TAG mixtures solid-liquid phase diagrams taken from literature. Compared to the adjustable Margules equation and traditional UNIFAC structural parameters approaches, results showed that the predictive modeling approach is quite helpful in representing the experimental data despite limitations in calculating the nonideal behavior of the systems. It is noticeable that using models for calculating the activity coefficients in both phases was essential to the systems’ best description. The SLE theory-based predictive modeling approach used here can be further evaluated for designing mixtures with desired phase behavior, being an interesting tool for describing phase diagrams of TAG mixtures when no experimental data is available.