Binary Mixtures of Tripalmitoylglycerol (PPP) and 1,3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP): Polymorphism and Kinetic Phase Behavior

Abstract

The kinetic phase behavior and phase transformation paths of tripalmitoylglycerol (PPP) and 1,3-dipalmitoyl-2-stearoyl-sn-glycerol (PSP) mixtures were investigated at 10.0°C/min (fast cooling) and 1.0°C/min (slow cooling) cooling rates, and re-heating at 5.0°C/min and 1.0°C/min. Mixtures with 0.1 X_PSP increments were studied in terms of polymorphism, crystallization and melting. At the higher cooling rate, all samples crystallized in the α polymorph, while at the lower cooling rate, samples containing X_PSP ≤ 0.3 crystallized in the α polymorph and samples containing X_PSP > 0.3 crystallized in the β′ polymorph. During heating all samples transformed to a more stable β′ form and melted finally in the β form (X_PSP ≤ 0.3) or in the β′ form (X_PSP > 0.3). Kinetic phase diagrams were determined from the DSC heating thermograms and XRD patterns obtained during cooling and heating and displayed a eutectic behavior with a eutectic point at X_PSP = 0.3 irrespective of the rate at which the samples were cooled and re-heated. The eutectic temperature was independent of the cooling and heating rates used. This study shows that PSP has a strong effect on the physical properties of PPP-PSP mixtures and dominates a large part of the phase behavior of the PPP-PSP binary system. At lower PSP concentration the mixtures transformed to the most stable β form, but at increasing PSP concentration the mixtures stabilized in the β′-phase which is preferred in many food application because this results in a smooth texture.

Practical applications: The results of this study are useful for the food industry as they can help in understanding the functionality of hard fat based structuring agents in end applications and in developing new triacylglycerol based crystallization and structuring agent for specific food applications.

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