Effect of oil properties on the formation and stability of Pickering emulsions stabilized by ultrafine pearl powder

Abstract

The aim of this study was to investigate the influence of oil properties on the formation and stability of Pickering emulsions stabilized by ultrafine pearl powder (UPP). Four types of oils, including alkanes, ester oils, vegetable oils and alcohol ether, were chosen as the oil phase to prepare the Pickering emulsions. The stability of the emulsions was characterized by the microscopy, measurement of droplet diameter and emulsion index (EI) within 28 days. The results indicated that the emulsified property of the UPP were of a great difference in different oils, which was affected by the combined impact of the dispersity of particles in oils, the contact angles and the oil–water interface tension. The droplet size of Pickering emulsions stabilized by UPP increased as the carbon chain length of branched alkanes decreased. For ester oils which containing a single ester group in the structure, ethylhexyl palmitate (EHP) formed more stable O/W emulsion due to the higher oil–water interface tension and the more moderate three-phase contact angles (oil–water-solid; θow). Furthermore, the caprylic acid triglyceride (CCT), simmondsia chinensis seed oil (SCS) and olive oil (OLO) formed W/O emulsions because of the higher three-phase contact angles, which may be explained by the adsorption of free fatty acids. Although the three-phase contact angles of PPG-15 stearyl ether (PSE) was intermediate relatively, the preparation of emulsion with PSE was not stable due to the lower oil–water interface tension.