Effect of fat crystal network structure on b-carotene bleaching

In recent years, bioactive lipophilic substances belonging to the lipid family have received an increasing interest due to their health protecting capacity. Unfortunately, they are highly prone to degradation through the development of oxidative reactions when added to foods. Although great efforts have been taken in the past to understand the chemical reactions involved in bioactive compound oxidation, only recently increasing attention has been paid towards the effect of lipid structure on oxidation rate. The presence of fat crystal networks could induce a cascade of chemical and physical chemical changes in the matrix able to modify the interactions among reactants and thus the kinetics of oxidation. This research was addressed to study the effect of fat crystal lattice structure on bleaching kinetics of β-carotene. To this aim, β-carotene was added to tripalmitin (PPP), tristearin (SSS), saturated monoglycerides (MG) and medium chain triacylglycerols (MCT) and their mixtures. Phase transition properties of fat and fat mixtures with and without β-carotene were studied by differential scanning calorimetry, synchrotron X-ray diffraction and polarized light microscopy. The β-carotene degradation was followed by measuring the changes in color and β-carotene concentration during storage at 20°C. Results evidenced that the structure of fat crystal lattice played a critical role in determining β-carotene stability. The location and compartmentalization of β-carotene resulted different depending on the fat considered. Results appear of considerable interest in the attempt to improve the stability of β-carotene in lipid containing foods as well as to design efficient delivery systems.