Kinetic Study on Alpha-Form Crystallization of Mixed-Acid Triacylglycerols POP, PPO, and Their Mixture

Abstract

The crystallization behavior of the metastable α form of triacylglycerols (TAGs) plays a critical role as a precursor for the crystallization of more stable β′ and β forms for various applications in food and pharmaceutical products. However, precise analysis of the crystallization kinetics of α has not been performed, likely due to its rapid and complex behavior. This paper presents the observation results of the initial stages of the isothermal crystallization kinetics of α forms of 1,3-dipalmitoyl-2-oleoyl-glycerol (POP), 1,2-dipalmitoyl-3-oleoyl-rac-glycerol (rac-PPO), and molecular compound (MC) crystals of a POP/rac-PPO (1/1) mixture (MCPOP/PPO) using synchrotron radiation time-resolved X-ray diffraction and polarized optical microscopy. In all the TAGs, α crystals with a worm-like morphology started to grow rapidly in the first stage. Then, the α crystals slowly transformed into more stable forms in different manners for different TAG samples. In POP, the conversion was simple, as the α-2 form transformed into γ-3, whereas in rac-PPO, the lamellar distance values of the α-2 form continuously decreased with time and changed into the α-3 form. In the MCPOP/PPO crystals, in contrast, separate crystallization of α-2 of a rac-PPO fraction initially occurred, followed by the crystallization of α-2 of POP, and the two α forms merged into α-2 of MCPOP/PPO. This separate crystallization was caused by large differences in the crystallization kinetics of the α forms of POP and rac-PPO.

Crystallization and Transformation Behavior of Triacylglycerol Binary Mixtures Forming Molecular Compounds of POP/OPO, POP/rac-PPO, and POP/sn-PPO

“…rac -PPO and sn -PPO crystallized into typical β′ form spherulites above 18 °C and into worm-like crystallites of α form below 18 °C. POP, MC POP/ rac ‑PPO , and MC POP/ sn ‑PPO formed worm-like α form crystals similar to rac -PPO below 14 °C. POP formed spherulites of γ-3L form between 14 to 20 °C; and MC POP/ rac ‑PPO and MC POP/ sn ‑PPO formed those of β′ form above 14 °C.…”

“…The isothermal growth rates, V , of each of the worm-like α crystallites and spherulites were determined by measuring the time evolution of the growing tips or the size of spherulites . The temperature dependencies of the crystal growth rates for the TAG samples are shown in Figure .…”

“…The isothermal growth rates, V, of each of the worm-like α crystallites and spherulites were determined by measuring the time evolution of the growing tips or the size of spherulites. 27 The temperature dependencies of the crystal growth rates for the TAG samples are shown in Figure 8. Above 18 °C, the growth rate of sn-PPO crystals (β′-3L) was significantly higher (by almost 2 orders of magnitude) than the others.…”

Solid phase behavior of mixture systems based on tripalmitoyl glycerol and monounsaturated triacylglycerols forming a molecular compound

“…This relates to a first separate crystallization of POP and PPO and next formation of α-2L (MC POP/PPO ). 30,31…”

Determining patterns in the formation of functional-technological properties of a fat-based semi-finished product in the technology of sponge cake products

“…It is determined in [36] that the implementation of the technological process of production of sponge-cake batter products significantly depends on the technological properties of the fat component, which affects the nutritional value, rheological, structural-mechanical, and physicochemical properties of finished products. It has also been analytically established that at present the range of fats and fat products that do not contain trans fats is limited.…”