Influence Of Sorbitan Trioleate On Crystallization Kinetics Of Palm Oil

Palm oil, which has the wide-developing prospects in tropical Hainan, is rich in natural resources. With important application in food industry, palm oil also has good thermal and oxidative stability. However,24℃refined palm oil is liquid at normal temperature, when the temperature is below20℃, clarified palm oil will become turbid. It needs to be heated repeatedly later in the process of storage, transportation and processing, not only affecting the quality of the products, but also increasing energy consumption. Therefore, finding a food additive to improve the weather resistance of the products is a issue which the production and application manufacturers are more concerned. We found that trace sorbitan trioleate (Span85)can effectively delay the crystallization behavior of palm oil in our experiment. In response to this phenomenon, we take the24℃refined palm oil added with trace(≤0.10%)Span85as the research model, using spectrophotometer and differential scanning calorimetry (DSC) to observe samples’ thermodynamics and kinetics of crystallization and melting process. Meanwhile, by means of Gompertz equation and the Avrami equation simulating experimental data to obtain exact parameter datum of crystallization process, such as the nucleation induction time (τ), crystal morphology (n), the rate constant (k), nucleation free energy (△Gc) et al., we could establish a mathematical model of crystallization. Analyzed by spectrophotometry and DSC methods, the results of experimental samples were simulated to get the crystallization behavior dynamics model of palm oil caused by trace Span85exactly explaining the changing process. With DSC testing its isothermal crystallization and melting behavior, the equilibrium melting point of samples is obtained by Hoffman-Weeks equation and the results showed that the application of Span85can make palm oil Tm0rise. Using Avrami equation to discuss the isothermal crystallization kinetics of samples, Avrami index n is obtained by simulation, the results indicate that adding additive Span85did not affect the crystalline form at a lower crystallization temperature rate. But under the DSC test conditions of lower crystallization temperature and rapid temperature changing rate, adding Span85will till not change the crystal dimension of palm oil. By calculating the half crystallization time t1/2, with the increasing amount of Span85, the1/2is rising, which indicated that this additive can hinder the crystallization of palm oil. Using the Gompertz equation to study the crystallization kinetics of samples, we obtain the simulated parameters including crystallization rate (k) and the crystallization induction time (τ)compared with parameters simulated by Fisher-Turnbull equation, indicating the opposite trend, the reason is that the growth rate depends on the number of available crystal nucleus in the process of crystal growth. In conclusion, using palm oil as a sample, Avrami and Gompertz model can be used to characterize the isothermal crystallization kinetics of fat with Span85. The experiment datum of dynamics parameters simulated by Hoffman-Weeks method and Fisher-Turnbull equation can completely elucidate the nucleation process and nucleus characteristics of palm oil samples.