Crystallization of Sunflower Oil Waxes
Journal of the American Oil Chemists' Society
Activation free energies of nucleation (ΔG c ) were calculated using induction times of crystallization measurements. Results showed that ΔG c decreased exponentially as wax concentration increased at a constant crystallization temperature (T c ). In contrast, for a constant supersaturation, ΔG c increased from 12 to 22°C but decreased between 22 and 35°C. Melting behavior of purified waxes and solutions of purified waxes in sunflower oil were studied by DSC after crystallization at fast and slow cooling rates (20 and 1°C/min, respectively). Low supercooling temperatures (T c >65°C) showed an increase in the onset temperature (T 0 ) as T c increased for both fast and slow cooling rates. Broader peaks were obtained for samples crystallized at a slow cooling rate at the same T c . Regarding the solutions of waxes in sunflower oil, the wax concentration (supersaturation of the system) controlled crystallization as well as T c . As T c increased, the enthalpy (ΔH) decreased at a constant wax concentration. When wax concentration decreased, ΔH decreased at a constant T c . For a low driving force, a small shoulder was obtained in the DSC diagrams owing to some type of fractionation. These results showed that wax crystallization is affected by different experimental parameters, such as T c and cooling rate, depending on the wax concentration of the sample.
Martini, S. and Añón, M.C. 2003. Crystallization of Sunflower Oil Waxes. Journal of the American Oil Chemists’ Society 80:525-532 (Impact Factor: 1.504)