Effect of Chemical Composition of Fat on Crystallization Behavior and Thermodynamic Parameters

ABSTRACT This study evaluates the activation free energy of crystallization of three fats (interesterified soybean oil [IESBO], interesterified palm olein [IEPO], and hydrogenated palm kernel oil [FHPKO]) by measuring induction times ( λ ) of crystallization. Three methods were used to measure λ : (a) through solid fat content (SFC) versus time (discrete method), (b) fitting SFC versus time to the Gompertz equation, and (c) using Differential Scanning Calorimetry (DSC). λ of crystallization was then used to calculate activation free energies of crystallization (Δ G c ). The Gompertz equation showed the most consistent data, hence the best method for crystallization analysis. When measuring SFC as a function of time T c for IESBO ranged from 30°C to 37°C and FHPKO ranged from 31°C to 36.5°C, while for IEPO, T c was between 24°C and 29.5°C. For IESBO, Gompertz fitting resulted in λ = 0.23 min ( T c = 30°C, with Δ G c = 10.3 KJ/mol) and λ = 34.7 min ( T c = 37°C, with Δ G c = 21.5 KJ/mol). Higher λ was observed for FHPKO at a similar temperature of T c = 31°C ( λ = 5 min) but lower Δ G c of 2.8 KJ/mol. At T c = 36.5°C longer λ was observed ( λ = 64 min, Δ G c of 8.6 KJ/mol) compared to IESBO. These results show that more energy must be delivered to crystallize IESBO samples compared to FHPKO for almost the same T c . For IEPO λ obtained through Gompertz fitting varied between 2.6 and 38 min at T c = 24°C and 29.5°C, respectively (Δ G c = 9.9–17.8 KJ/mol). For a supercooling of approximately 10.7°C, Δ G c were 9.5, 2.3, and 0.5 KJ/mol for IESBO, IEPO, and FHPKO, respectively. This suggests that even for the same supercooling, more energy is required to crystallize IESBO, followed by IEPO and that least energy is required for the FHPKO sample.