Crystallization Behavior of Vegetable Fats through the Technique of
Polarized Light Microscopy
Fernanda Campos Brito Nuno1, Luis Antonio Gioielli2, Lireny Aparecida Guaraldo
Gonçalves1 and Renato Grimaldi1
1
Laboratório de Óleos e Gorduras / DTA / FEA / UNICAMP, CP 6091, CEP 13083-970,
Campinas, SP, Brasil
2
Departamento de Tecnologia Bioquímico-Farmacêutica, FCF, USP, CP 66083,
CEP 05315-970, São Paulo, SP, Brasil
The vegetable oils are used as raw materials in many industrialized products and they
possess great importance, considering both the technological and the sensorial aspect,
fundamental for their acceptance by the consumer. The texture of food products based
on fats is strongly influenced by the structural and mechanical properties of their
crystals network. The process of partial hydrogenation, responsible for the presence of
trans fatty acids in the foods has been substituted by alternative processes, seeking the
elimination of these isomers. The substitution of partially hydrogenated oils by other
sources, mainly palm oil and of palm kernel oil, needed to suffer several adaptations
besides of process, due to the differences of behavior of these sources, mainly in the
crystallization aspect. In this work the polarized light microscopy was used to capture
images of the crystals of palm oil (PO), palm kernel oil (PKO), partially hydrogenated
soy oil (HSO) and partially hydrogenated cotton oil (HCO), at 20ºC and 25ºC with
crystallization times of 4 and 24 hours. These images were used to obtain the mean
diameter and the number of crystals. The crystals of HCO and HSO, after 4 hours of
crystallization at 20ºC, had already reached their maximum size. The crystals of PKO,
imported PO and national PO presented growth within the first 4 hours up to 24 hours of
crystallization. At 25ºC, the crystals had already reached their maximum crystallization
after 4 hours. Just PKO, for presenting melting point close to 25ºC, didn't crystallize.
The behavior of crystallization of HCO and HSO was very similar, while PKO presented
the largest crystal among the evaluated samples.