Effect of Oil Phase Transition on the Stability of Pickering Emulsions Stabilized by Cellulose Nanocrystals

Emulsifier design is one of the key strategies in interfacial engineering for emulsion stability. In this study, cellulose nanocrystals (CNCs) were used as an interfacial stabilizer to improve the stability of coconut oil (CO)-in-water emulsions. A Pickering emulsion consisting of CO and water was optimized based on four parameters using the response surface methodology and the central composite design. The droplet coverage remained stable during the crystallization of the oil phase when the temperature was reduced below the melting temperature of CO. Fluorescent-labeled CNCs were used to monitor the partitioning of CNC at the O/W interface during the crystallization of CO. The Generation 6 polyamidoamine (G6 PAMAM) dendrimer covalently grafted on the surface of CNC was used as an intrinsic fluorescent dye. Since it displayed similar properties as the emulsifier, it could be used to monitor the CNC coverage on the oil droplets at various temperatures. The fluorescence micrographs showed that the emission of PAMAM CNCs at the O/W interface remained on both the liquid and solid CO droplets, confirming that oil crystallization did not affect the fluorescent CNC coverage on the oil droplets.