Multi-length-Scale Elucidation of Kinetic and Symmetry Effects on the Behavior of Stearic and Oleic TAG. I. SOS and SSO

Positional isomerism in triacylglycerols (TAG), present in a molecular ensemble arising from genetic, environmental or processing-induced changes, can result in significant differences in the macroscopic physico-chemical functionality of crystallized networks of the ensemble. The differences in phase behavior induced by positional isomerism and levels of unsaturation of pure oleoyl-distearoyl TAG (SOS, SSO) were detailed at different length scales. The effect of cooling rate on the polymorphism, thermal properties and microstructure were systematically investigated between 0.1 and 5 °C/min. The symmetrical SOS presented a complex polymorphism and microstructure, which varied predictively with cooling rate. The crystal phases and transitions observed for this TAG are similar to those of cocoa butter. In contrast, the cooling rate had limited effect on the phase behavior of the asymmetrical SSO. The differences between the crystallization of SSO and SOS induced by kinetics are related to the kinked oleic acid at the outer position in the SSO molecule and favorable end group structure for SOS. The fundamental understanding gained from such model systems can be used in many industrial formulations, particularly foods.