Thermal and structural behavior of mango (Mangifera indica L) kernel fat from three Ivorian varieties

Abstract

Mango (Mangifera indica L.) seeds is an interesting source of fat, rich in stearic (St) and oleic (O) acid with three major triacylglycerols (TAG): StOSt, StOO, and StLSt. The kernel fat content and quality depend however on the varieties and their origin. The objective of this study was to investigate the crystallization and polymorphic behavior of mango kernel fat extracted from three selected Ivorian varieties which differ in terms of TAG composition: Kent (KT), Djakoumankoun (DN) and Brooks (BR). The isothermal crystallization behavior was examined at 15 and 20°C by pulsed nuclear magnetic resonance, differential scanning calorimetry, x-ray diffraction (XRD) and polarized light microscope. Under static conditions, DN crystallized faster, followed by BR, then KT. At 15°C, an unusual evolution was observed for both DN and BR, which can be explained by a melt-mediated polymorphic transition from α into more stable forms. Using a differential scanning calorimetry (DSC) stop-and-return technique, different crystallization behaviors were also observed. Isothermal XRD experiments confirmed that the kinetics of the polymorphic transformation was different within the three samples, even if the three fats were β-3L-tending. At 15°C, KT transformed from liquid state to stable form without passing through α-form, while DN and BR crystallized first into α-from which transformed further to β′, then into stable β-form. At 20°C, DN and BR crystallized directly from liquid to β′, which later transformed into β-form while KT did not crystallize under the same conditions. The huge differences observed result from the differences in the TAG profiles, mainly in the StOO and StOSt content.