Stability and characterization of O/W free phytosterols nanoemulsions formulated with an enzymatically modified emulsifier

Phytosterols (PS) are bioactive compounds with confirmed hypocholesterolemic activity. PS are added to foods to formulate functional products through different procedures. One of the most promising approaches for bioactive compound delivery are nanoemulsions (NE), which offer protection and allow their dispersion in aqueous matrices. Phosphatidylcholine (PC) is a natural emulsifier which can be modified enzymatically to improve its functionality, for example as lysophosphatidylcholine (LPC). The objective of this study was to evaluate the physico-chemical characteristics of free phytosterols O/W NE formulated with PC and LPC. NE were prepared using a 10:1 ratio of emulsifier:phytosterols, 4% medium chain triglycerides, 30% glycerol and 55% water. Emulsion stability was evaluated at 37 °C and 4 °C for 12 days by monitoring particle size and peroxide value. Translucid and homogeneous NE were obtained using both formulations, which were free of sediment or floccules and with a mean globule diameter within the NE range. During storage NE prepared with LPC were less stable, despite of their higher water affinity, than NE prepared with PC. Storage temperature produced an acceleration of physical and chemical instabilities; the oxidation rate in the NE was influenced by temperature and the degree of unsaturation of fatty acids in the emulsifier.