β-Carotene degradation kinetics as affected by fat crystal network and solid/liquid ratio

The aim of this research was to study beta-carotene degradation kinetics into lipid systems containing different fat crystal networks in the presence of increasing liquid oil amounts. To this purpose, fat blends containing liquid saturated medium chain triacylglycerols (MCT) with increasing content of saturated monoglycerides (MG), tripalmitin (PPP) and tristearin (SSS) were added with 0.6 mg/g beta-carotene. The fat crystal networks formed in the fat blends were characterized by using polarized light microscopy and synchrotron X-ray diffraction (XRD). In addition, A-carotene degradation was monitored during storage in the dark at 20 degrees C. Results highlighted that fat crystallization could differently affect beta-carotene stability. In bulk SSS and PPP, beta-carotene degradation proceeded at comparable rate, whereas when the saturated liquid oil MCT is included in the fat network, the rate of oxidation slightly decreased. Interestingly, the oxidation rate was not significantly affected by the solid/liquid ratio of the systems. A completely different behavior was observed in MG containing systems: the rate of beta-carotene oxidation was in every case significantly lower than that observed in SSS and PPP containing samples. Also in this case, the MG protective effect was independent on its content in the fat mixtures.