Development and photostability of transparent microemulsions delivering b-carotene and curcumin

Microemulsions are optical transparent or slightly opalescent colloidal systems with a mean droplet diameter between 10 and 100 nm. They can be prepared by using low energy methods, such as that of phase inversion temperature (PIT). Microemulsions have been indicated as an efficient tool to delivery lipophilic molecules, such as colorant or bioactive molecules, into foods due to their capacity to improve the solubility and the stability of the loaded compound. This research was addressed to develop transparent microemulsions by PIT method delivering curcumin and β-carotene. To this aim, different oils (i.e. extra virgin olive oil, medium chain triacylglycerols and peanut oil) were considered as bioactive molecule carrier into microemulsions. The systems were characterized by recording the visual transparency and by determining the mean droplet size. Afterwards, the photostability of curcumin and β-carotene in microemulsions was studied during storage at 20°C under increasing light intensity from 0 to 6000 lx. Data were elaborated by using the most appropriate kinetic models. Results evidenced that the lipid type greatly affected the emulsion physical stability as well as the photostability of β-carotene and curcumin. In particular, the photostability of β-carotene was higher than that of curcumin in all considered systems. Moreover, the presence of extra virgin olive oil in the emulsion allowed to decrease the degradation rate of oxidation of both bioactives probably due to the presence of natural antioxidants. These findings appear of considerable interest in the attempt to design efficient delivery systems to be exploited in food formulations.