Isothermal crystallization of hydrogenated sunflower oil: I- Nucleation

HERRERA M.L.; FALABELLA C.; MELGAREJO M.; AÑON, MARÍA C.

JOURNAL OF THE AMERICAN OIL CHEMISTS SOCIETY (JAOCS)

SPRINGER

Lugar: Berlin; Año: 1998 vol. 75 p. 1273 - 1280

0003-021X

Nucleation kinetics of sunflower seed oil, whichwas hydrogenated under two different conditions, was studiedby means of a polarized light microscope and an optical setupwith a laser as the light source. When the laser was used, observedinduction times were shorter than the ones measured bythe microscope. The laser method was found to be more sensitiveand accurate. Two different crystallization behaviors werefound depending on the chemical composition of the samples.Samples with high content of trielaidin crystallized in the β format temperatures close to the melting points. They exhibited bothβ′ and β forms depending on crystallization temperature, ashappens in natural semisolid fats such as palm oil. Samples withhigh content of mixed oleic and elaidic triacylglycerols crystallizedin the β′ form even at temperatures close to the meltingpoints and they did not show β form under the conditions usedin this study. Activation free energies of nucleation for hydrogenatedsunflower seed oil were low for the two hydrogenationconditions. It can be concluded that nucleation of sunflowerseed oil is a fast process and initially needs low supercooling.These results are also important from a practical point of viewfor processing design, especially in regards to processes inwhich fats should be completely crystallized by the end of theproduction line.