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Crystallization of sunflower oil waxes
Author(s) -
Martini S.,
Añón M. C.
Publication year - 2003
Publication title -
journal of the american oil chemists' society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.512
H-Index - 117
eISSN - 1558-9331
pISSN - 0003-021X
DOI - 10.1007/s11746-003-0732-y
Subject(s) - wax , crystallization , supersaturation , supercooling , nucleation , sunflower oil , enthalpy , materials science , chromatography , chemistry , analytical chemistry (journal) , thermodynamics , biochemistry , organic chemistry , physics
Abstract Activation free energies of nucleation (Δ G c ) were calculated using induction times of crystallization measurements. Results showed that Δ G c decreased exponentially as wax concentration increased at a constant crystallization temperature ( T c ). In contrast, for a constant supersaturation, Δ G 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 (Δ H ) decreased at a constant wax concentration. When wax concentration decreased, Δ H 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.