Using Mettler Dropping Point Data from Dilute Soybean Oil-Triglyceride Mixtures to Estimate Thermodynamic Properties for Corresponding Pure Triglyceride

Abstract

The enthalpy of fusion and melting temperature for ten symmetrical and seven asymmetrical triglycerides (TAGs) was estimated using mettler dropping points (MDP) of five concentrations of TAGs dissolved in a complex mixed solvent (soybean oil) and a modified Clapeyron equation, an approach we refer to as LIST estimation. The ten estimates generated using the LIST method were compared for accuracy to values measured using differential scanning calorimetry and MDP of pure TAG samples and to estimates calculated using effective carbon number and the Triglyceride Property Calculator. We find that LIST estimates for stearic acid and palmitic acid-based monoacid and symmetrical TAGs agree well with measured and calculated values using alternative methods. Conversely, LIST estimates for stearic acid and palmitic acid based asymmetrical TAGs diverge substantially from alternative estimates, suggesting that the LIST approach is inadequate in describing asymmetric TAGs using the assessed concentrations of TAG in soybean oil. Elaidic acid containing TAGs behaved uniquely, with LIST estimates for trielaidin not agreeing with alternative estimates yet LIST estimates for distearic–monoelaidic in both symmetric and asymmetric configurations agreeing well with alternative estimates. We conclude that the LIST approach of using MDP of a high melting pure TAGs dissolved in soybean oil can be, at minimum, a viable approach in estimating melting behavior properties of symmetric stearic and palmitic acid containing TAGs. Further investigation for the behavior of asymmetric stearic and palmitic acid containing TAGs in soybean oil is required. As such, using known enthalpies of symmetric stearic and palmitic acid containing TAGs, we should be able to estimate the solubility of a high melting pure TAG in soybean oil using MDP and Clapeyron’s equation.