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Comparative Analysis of Thermal Behavior, Isothermal Crystallization Kinetics and Polymorphism of Palm Oil Fractions
College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, Guangdong, China
Guangdong Province Key Laboratory for Green Processing Of Natural Products and Product Safety, Guangzhou 510640, Guangdong, China
* Author to whom correspondence should be addressed.
Received: 5 November 2012; in revised form: 31 December 2012 / Accepted: 7 January 2013 / Published: 15 January 2013
Abstract: Thermal behavior of palm stearin (PS) and palm olein (PO) was explored by monitoring peak temperature transitions by differential scanning calorimetry (DSC). The fatty acid composition (FAC), isothermal crystallization kinetics studied by pulsed Nuclear Magnetic Resonance (pNMR) and isothermal microstructure were also compared. The results indicated that the fatty acid composition had an important influence on the crystallization process. PS and PO both exhibited more multiple endotherms than exotherms which showed irregular peak shapes. An increasing in cooling rate, generally, was associated with an increase in peak size. Application of the Avaimi equation to isothermal crystallization of PS and PO revealed different nucleation and growth mechanisms based on the Avrami exponents. PS quickly reached the end of crystallization because of more saturated triacylglycerol (TAG). The Avrami index of PS were the same as PO under the same isothermal condition at lower temperatrue, indicating that the crystallization mechanism of the two samples based on super-cooling state were the same. According to the polarized light microscope (PLM) images, crystal morphology of PS and PO was different. With the temperature increased, the structure of crystal network of both PS and PO gradually loosened.
Keywords: fractional crystallization; thermal behavior; isothermal crystallization kinetics; polymorphism
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Zhang, X.; Li, L.; Xie, H.; Liang, Z.; Su, J.; Liu, G.; Li, B. Comparative Analysis of Thermal Behavior, Isothermal Crystallization Kinetics and Polymorphism of Palm Oil Fractions. Molecules 2013, 18, 1036-1052.
Zhang X, Li L, Xie H, Liang Z, Su J, Liu G, Li B. Comparative Analysis of Thermal Behavior, Isothermal Crystallization Kinetics and Polymorphism of Palm Oil Fractions. Molecules. 2013; 18(1):1036-1052.
Zhang, Xia; Li, Lin; Xie, He; Liang, Zhili; Su, Jianyu; Liu, Guoqin; Li, Bing. 2013. "Comparative Analysis of Thermal Behavior, Isothermal Crystallization Kinetics and Polymorphism of Palm Oil Fractions." Molecules 18, no. 1: 1036-1052.