《Binary Phase Behavior of 1》.pdf

J Amer Oil Chem Soc (2007) 84:219–227 DOI 10.1007/s11746-006-1034-0 ORIGINAL PAPER Binary Phase Behavior of 1,3-Dipalmitoyl-2-oleoyl-sn-glycerol and 1,2-Dioleoyl-3-palmitoyl-rac-glycerol L. Zhang Æ S. Ueno Æ S. Miura Æ K. Sato Received: 9 August 2006 / Accepted: 15 December 2006 / Published online: 23 January 2007 AOCS 2007 Abstract 1,3-Dipalmitoyl-2-oleoyl-sn-glycerol (POP) formed. A time-resolved synchrotron radiation X-ray and 1,2-dioleoyl-3-palmitoyl-rac-glycerol (OOP) are diffraction study undertaken during the cooling and two major molecular species that account for roughly heating processes indicated that the a and b¢ forms of half of the total triacylglycerols in palm oil. The the POP and OOP fractions crystallized and melted in binary phase behavior of a POP/OOP mixture plays separate manners, and that crystallization of the b¢ an important role in the crystallization of palm oil. form and the polymorphic transformation from a to b¢ We conducted thermodynamic and kinetic studies of of POP and OOP are promoted in the presence of OOP and its mixtures with POP using differential another component. The absence of molecular com- scanning calorimetry and X-ray diffraction with a pound crystals in the binary mixtures of POP/OOP is conventional generator and synchrotron radiation. We explained by taking into account the molecular found that OOP has two polymorphs, a as a meta- interactions of acyl chain packing, glycerol confor- stable form and b¢ as the most stable form, and that mation, and methyl end stacking, among which glyc- the two forms are stacked in a triple-chain-length erol conformation appeared to be most influential. structure. The POP/OOP mixtures exhib