Phase behaviour of model triglyceride ternary blends: triolein, tripalmitin and tristearin

Abstract

We investigate the phase behavior of model ternary triacylglycerol blends, comprising triolein (C₅₇H₁₀₄O₆, OOO), tripalmitin (C₅₁H₉₈O₆, PPP) and tristearin (C₅₇H₁₁₀O₆, SSS), building upon extensive characterisation of single and binary mixtures, in order to rigorously map the thermal transitions of model natural ‘fats’. A combination of calorimetry, X-ray diffraction, and FTIR spectroscopy is employed to determine crystallisation and melting temperatures and identify the corresponding phases in the complex ternary system. We recover the eutectic behaviour of SSS-PPP blends and the invariability of OOO neat transitions, and resolve the complex β′ + β ternary surface, reflecting the roles of unsaturation and polymorphism of its constituents. Our results provide a representation of the OOO:PPP:SSS:temperature phase behaviour into a triangular prism, consistent with binary pair-wise data, which can inform a range of food science, cosmetic, pharmaceutical and cleaning applications that depend strongly on the physical-chemistry of such multicomponent ‘triglycerides’.