INFLUENCE OF CIS AND TRANS DOUBLE-BONDS ON THE THERMAL AND STRUCTURAL-PROPERTIES OF MONOACID TRIGLYCERIDES

In order to determine the importance of cis or trans unsaturations from a technological point of view, the study of the structural and thermal properties of monoacid triglycerides: tristearin (SSS), triolein (OOO) and trielaidin (EEE) has been undertaken. X-ray powder diffraction and differential scanning calorimetry are useful tools to elucidate the physicochemical properties of such compounds. In this work polymorphism, kinetics of polymorphism and intersolubility have been investigated. From a structural point of view, we have shown that, according to the polymorphic form, the conformational properties of EEE are similar to those of the corresponding saturated molecule SSS or to those of the cis unsaturated analogue OOO. The study of the intersolubility behavior of these three compounds has shown a different affinity of the cis and trans unsaturated molecules vs the completely saturated one. By the same method, we have observed that trans unsaturated hydrocarbon chains cocrystallize with both cis-unsaturated (OOO) and totally saturated hydrocarbon chains (SSS); the trans double bond of EEE can adapt to the two kinds of lattices. The study of the kinetics of polymorphism has shown that 5% of OOO or EEE accelerate the β′→β transition of SSS, while the reason for the two phenomena is quite different. The adaptation of EEE to cis-unsaturated and to saturated hydrocarbon chains shown in the structural and intersolubility behavior analyses also appears in the kinetic study, after adjunction of 5% of OOO into EEE. All the results confirm that, from structural and thermal points of view, EEE has an intermediate behavior between SSS and OOO. © 1990 AOCS Press.