Optimizing sub-critical water extraction of canola proteins for novel plant-based emulsifier application

A novel sub-critical water extraction method was utilized to recover functional canola proteins from the de-oiled meal. Sub-critical water extraction is an emerging green technology in which water under high pressure and high temperature remains in a subcritical state. The objective of this research was to optimize the subcritical extraction process to improve the functional properties and maximize the extraction yield of canola proteins. The functional protein was then utilized as an emulsifier in the development of O/W emulsions. The sub-critical extraction was performed by varying extraction parameters, including time (20-30min), temperature (200-250°C), and feed concentration (5%-20%). Optimization was performed using a central composite design, leading to a maximum protein yield of 68.9% with a hydrolysis (DH) degree of 9.2% at 225°C, 25 min and 5% feed concentration. Hydrolysis of proteins changed its structure, causing alteration of the functional properties such as their interfacial tension, reaching a minimum of 3.9 mN/m with 14.1% DH at 250°C, 30 min and 5% feed concentration. A less severe treatment at 200°C and 20% feed concentration led to the product with a lower DH of 2-4% with higher interfacial tension of about 11.6 mN/m. A significant amount of phenolic compounds were also recovered by the sub-critical water extraction process. The extracted hydrolyzed canola proteins with varying degrees of hydrolysis and surface activity were then used to develop oil-in-water emulsions with 0.5% protein and 1% oil concentration. The extracts with the lowest interfacial tension and maximum degree of hydrolysis corresponded to the highest emulsion stability. Despite eventual creaming during 1-week storage, the samples with optimized extraction conditions exhibited comparatively less creaming and improved stability aginst droplet coalescence. Overall, this research provides valuable insights into optimizing sub-critical extraction parameters for enhanced protein recovery and functionality, showcasing applications in stable emulsion development.