Palm Oil Dry Fractionation with Stearin Blending

Palm oil is the most consumed oil worldwide. Its composition confers technological properties that no other vegetable oil can afford. It is also the most fractionated oil with a huge potential in multi-step dry fractionation. Different routes are clearly established leading to specialty products like low IV super stearin (solid route), high IV top olein (liquid route) and hard palm mid fraction (ingredient for CBE).
This work focused on the liquid route, more particularly on the first step: production of olein (IV 56) and stearin from palm oil. The initial objective was to find a way to improve the olein yield thanks to an optimization of the palm oil composition with stearin blending.
To this end, palm oil was blended with increasing amounts of palm stearin to obtain matrices with variable tri-saturated triglyceride contents; five blends were investigated. Dry fractionation was carried out on pilot scale using a Tirtiaux crystallizer coupled to a high-pressure membrane press filter.
After optimization of the cooling curves, on-going crystallization was monitored by sampling using optical microscopy and powder X-Ray diffraction. Crystallization kinetics were derived from solid fat content of the slurry by p-NMR, iodine values and DSC cloud points of the olein after vacuum filtration. Press filtrations were then performed at identical temperature after the same crystallization time. Fractions quality was evaluated based on iodine value, DSC cloud point and triglyceride composition by HPLC.
It was shown that one specific matrix could release more olein after press filtration in identical conditions. This olein was characterized by slightly higher iodine value and surprisingly higher DSC cloud point. This matrix was also the fastest to achieve a steady state during the crystallization kinetics.
All the analytical tools used helped in understanding and trying to elucidate this unexpected behavior.