Stabilization of Emulsions Prepared using Sub-critically extracted Hydrolyzed Canola Proteins using a Bilayer Interfacial Approach

This study aimed to valorize desolventized toasted canola meal using sub-critical water extraction, to recover functional hydrolyzed proteins with optimal interfacial tension (IFT), degree of hydrolysis (DH) and emulsion stabilization property. A central composite design was used to optimize extraction conditions of temperature (200–250°C), time (20–30 min), and feed concentration (5–20%) at 4.03 MPa. The extracted proteins displayed an IFT ranging from 11.6 mN/m to a minimum of 4.0 mN/m, while the DH varied from 2.3% to 14.1%. Based on the DH, two sets of extracts containing hydrolyzed proteins were chosen for emulsion development: set-1 with a low DH (2-5%) and set-2 with a high DH (9-15%). Both sets of emulsions destabilized over 1-week storage, with a significant increase in droplet size and cream layer separation, due to the inability of the hydrolyzed proteins to remain at the droplet interface and form a stable, elastic interface to resist droplet coalescence. Therefore, the most unstable emulsion (T225-t25-FC12.5) with the largest increase in droplet size was selected for bilayer formation around the oil droplets by adding chitosan at different pH (2-7) values. The bilayer improved emulsion stability by creating a more elastic interface. Bilayer emulsions at pH 2, 4, 5, and 6 retained droplet sizes (0.56–0.65 µm) over 4 weeks and displayed no visual creaming, in contrast to the primary emulsion showing extensive coalescence, with droplet size increasing from 0.59 to 2.09 µm. The bilayer emulsions also displayed a high positive zeta potential ranging from 56.7 mV to 32.17 mV. However, emulsion at pH 7, with low zeta potential (15.3 mV) displayed a rapid destabilization. Overall, this research provides valuable insights into stabilizing the hydrolyzed protein-stabilized emulsions using a bilayer formation approach by creating a more elastic interface, which can stabilize the emulsions against coalescence.