Effects of high-energy emulsification methods and environmental stresses on emulsion stability and retention of tocotrienols encapsulated in Pickering emulsions

Abstract

Pickering emulsion is a promising medium for encapsulating oil-soluble bioactive. However, the effects of emulsification method on the retention of sensitive bioactive encapsulated in Pickering emulsions have often been overlooked. In this work, alginate-coated chitosan-stabilized Pickering emulsion (ACPE) was used as a medium for the microencapsulation of a highly concentrated tocotrienol-rich fraction (TRF). TRF is known to be a potent vitamin E (tocols), but it is easily oxidized. We investigated the influence of microfluidization and ultrasonication parameters on the droplet size, emulsion stability, and tocols retention upon processing and during storage. Microfluidization of the Pickering emulsions containing TRF (TRF-ACPE) at 50 MPa for one pass resulted in a monomodal size distribution with a mean droplet size of 0.96 ± 0.02 μm and a span of 1.56 ± 0.04. Further increase in the microfluidization pressure and number of passes showed negligible effect on the mean droplet size. On the contrary, ultrasonication resulted in TRF-ACPE of larger mean droplet sizes and polydispersed size distributions at all processing conditions. Moreover, higher ultrasonication intensity (90%) and longer duration (4 and 8 min) were found to induce ‘oiling-off’. The TRF-ACPEs prepared with both emulsification methods showed negligible degradation (<0.1%) of tocols upon processing. This exemplified a significant improvement in the tocols retention upon processing with a 4 to 25-fold enhancement compared to the surfactant-stabilized emulsions reported in the past literature. Our findings suggest that alginate-coated chitosan stabilized Pickering emulsion can be used to improve the stability of sensitive bioactive, which is useful for the development of functional foods. • Stable 10 wt% tocotrienols-loaded Pickering emulsion was successfully prepared. • Emulsification methods affected droplet size, emulsion stability and tocols stability. • Microfluidization produced uniform and monodispersed Pickering emulsion droplets. • Ultrasonication induced ‘oiling-off’ in the Pickering emulsion at 90% amplitude. • Pickering emulsion improved the tocols retention upon processing and during storage.