Morphology of monosaturated triacylglycerol crystals in different crystallization procedures

Abstract

The morphology of triacylglycerol (TAG) crystals significantly affects the efficiency of their fractionation during the processing of fats and oils to improve their functionality. Large stable crystals, formedby fast crystallization, improve the fractionation efficiency. The purpose of this study was to determine optimal crystallization to improve the morphology of stable β form crystals that are suitable for dry fractionation. The polymorphic transformation behaviors from unstable forms to stable forms were investigatedby polarizedlight microscopy and X-ray diffraction. The solid-solid transformation of unstable α and β' forms of monosaturatedTAGs into β forms was investigated. The β form was nucleatedin the β' form and grown, by solid-solid transformation, to a larger crystal to improve its separation efficiency. In contrast, the β form transformedfrom the α form retainedthe original morphology of the α form. The size of the obtained β form crystals increasedwith an increase in the crystallization temperature of the initial β' forms. The temperature of polymorphic transformation affectedthe rate of transformation, while the influence of temperature on the size of transformedcrystals was limited. We also clarifiedthe influence of the difference in fatty acidchain length of the examinedTAGs. The present study demonstrated that crystal morphology can be modified, depending on the crystallization procedure, to improve the fractionation efficiency.