Crystallization kinetics of coconut oil based on Avrami model
2016
Fardiaz, D. | Hariyadi, P. | Mursalin | Purnomo, E.H. | Andarwulan, N.
It has been shown experimentally by many researchers that cooling rate and crystallization temperature affect the rate of crystal formation. In this study, crystallization kinetics of coconut oil was measured by monitoring the solid fraction of the oil using pulsed Nuclear Magnetic Resonance (pNMR). Four levels of cooling rate and crytallization temperature were studied. Parameters of crystallization kinetics are quantified by applying Avrami model. Avrami model was used to explain the mechanism of nucleation (Avrami index), crystallization rate constant and crystallization half-time. Crystallization was done by heating the oil at a temperature of 70°C for 10 minutes prior to rapid cooling to 29°C. Then, rate of cooling from 29°C to the crystallization temperature (critical cooling rate) was set below 2°C/minutes. During the process, the oil was stirred at 15 rpm. Solid fraction was measured periodically since the crystallization temperature was reached until maximum solid fraction was achieved. The results showed that Avrami model is able to quantitatively describe coconut oil crystallization kinetics. Lower critical cooling rate decreases Avrami index, crystallization half time but increases crystallization rate constant. Crystallization temperature has positive correlation with the crystallization rate contstant and Avrami index.
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