Curcumin loaded microemulsions prepared by phase inversion temperature (PIT) method: effect of formulation on curcumin degradation

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 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 curcumin-loaded microemulsions by PIT method and to study the effect of microemulsion formulation on curcumin stability. To this aim, lipids (i.e. extra virgin olive oil, tristearin, saturated monoglycerides,) showing different physical properties were considered as curcumin carrier into microemulsions. The systems were characterized by recording the visual transparency and by determining the mean droplet size. Curcumin degradation kinetics in microemulsions were determined during storage at 20°C by using HPLC analysis. Results evidenced that the lipid type greatly affected the curcumin stability. In particular, fat crystallization seemed to play a critical role in determining degradation kinetics. These findings appear of considerable interest in the attempt to design efficient delivery systems.