This research was addressed to study the effect of lipid physical state on bleaching kinetics of â-carotene. To this aim, â-carotene was added to palm oil and palm stearin and the samples were stored at increasing temperatures allowing different degree of crystallization. Phase transition properties of palm derivatives were studied by differential scanning calorimetry and synchrotron X-ray diffraction, whereas â-carotene bleaching kinetics were followed by measuring color changes. Bleaching proceeded at comparable rate in palm oil and palm stearin containing systems stored at 20 and -18 °C, whereas the color changes showed a maximum rate at 4 °C in palm stearin samples and at -7 °C in palm oil systems. Arrhenius plot clearly highlighted deviations from the linearity underlining the crucial role of lipid physical properties in determining the bleaching rate. The location and the compartmentalization of â-carotene in the fat lattice could affect its chemical stability.
Calorimetry, Differential Scanning Chemical Phenomena