Crystallization kinetics of palm stearin in blends with sesame seed oil

This study investigates the crystallization kinetics of palm stearin (PS), a palm oil fraction, in blends with sesame seed oil. The results indicate that the crystallization behavior of PS in sesame oil is mainly associated with the crystallization of tripalmitin. Therefore, crystallization of blends of 26, 42, 60, and 80% (wt/vol) PS in sesame oil was described by equations developed for simpler systems (e.g., Fisher and Turnbull equation). The isothermal crystallization, melting profile, and fitting of the kinetics of nucleation to the Fisher and Turnbull equation showed that the 26, 42, and 60% PS/sesame oil blends crystallized mainly in the beta(1)' polymorph state, in contrast, the 80% blend crystallized in two different polymorph stares (i.e., beta(1)' at T less than or equal to 307.6 K and beta(1) at T greater than or equal to 308.2 K). The data indicated that, in spite of the higher concentration of PS in the 80% PS/sesame oil system, crystallization in the beta(1) state required more free energy for nucleation (Delta G(c)) than beta(1)' crystallization in the 26, 42, and 60% PS/sesame oil. At the low cooling rate used (1 K/min) it was observed that, for a particular PS blend, the higher the effective supercooling the higher the viscosity of the oil phase and the smaller the induction time of crystallization (T-i). Additionally, the beta(1)' crystals from PS, developed at the highest effective supercooling investigated, were smaller than the beta(1) crystals obtained at lower effective supercooling.