DETERMINATION OF PHYSICAL PROPERTIES AND CRYSTALLIZATION KINETICS OF OIL FROM ALLANBLACKIA SEEDS AND SHEA NUTS UNDER DIFFERENT THERMAL CONDITIONS

In this study, the fatty acid content, melting and cooling profiles, crystallization properties at different cooling rates and kinetics of crystallization of Allanblackia seed oil (ASO) and shea nut oil (SNO) are investigated. The fatty acid content is determined using gas chromatography coupled with mass spectrometry (GC/MS). The melting and cooling profiles, crystallization, and crystallization kinetics are investigated using differential scanning calorimetry (DSC) and the fat morphology is investigated using polarized light microscopy. The GC/MS results showed that ASO contains a high amount of saturated fats as compared with SNO. The DSC analysis revealed that ASO has a high melting temperature of 35.3 ± 2.1 °C and crystallizes earlier (16.8 ± 0.3 °C) in the constant rate cooling experiments. The crystallization patterns of both oils are observed to be dependent on the cooling rate. Under isothermal conditions, it is observed that both ASO and SNO shows high and low melting peaks with the low melting peak disappearing as the crystallization progressed. The Avrami model is used to estimate the crystallization kinetics of the oils under the isothermal conditions and it is inferred that ASO has a faster nucleation and subsequent crystal growth as compared with SNO. At room temperature SNO formed overlapping fat crystal particles while ASO gave distinct crystallized fat fractions during the crystallization at room temperature, as shown by the polarized light microscopy.

Practical Application: The high melting temperature, the rate and the nature of crystallization of Allanblackia seed oil gives it good material functionality and desired plasticity, properties associated with possible industrial application. Additionally, the presence of high stearic acid content makes the Allanblackia seed oil a healthy choice for food, hence, it can be used as a substitute for cocoa butter in the food industry.