Effect of Sodium Caseinate/Cellulose Nanocrystals Addition on the Physical and Oxidative Stability of Red Palm Olein-in-Water Pickering Emulsions

Abstract

This work investigated the use of a dual biopolymer system containing cellulose nanocrystals (CNC) and sodium caseinate (SC) for red palm olein-in-water (O/W) Pickering emulsion stabilisation. The effect of CNC particle concentration at a constant amount of SC on emulsion properties was particularly studied.The resultant mixed biopolymer-based emulsions were characterised for droplet size distribution, zeta potential, creaming index and microstructure, as well as primary and secondary oxidation products by oxidation tests at 90˚C. Results showed that creaming stability was relatively high for SC/CNC-stabilised emulsions compared to emulsions prepared with SC alone. Increasing CNC concentration from 0.25% to 1.00% (w/v) resulted in a gradual decrease in emulsion droplet size with increased surface negative charges. Higher CNC content induced a marked reduction in the lipid oxidation of SC/CNC-stabilised emulsions. The mixed SC/CNC biopolymer significantly improved the carotene retention of emulsions during the accelerated oxidation test. Emulsions comprising 1.00% SC and 1.00% CNC presented the highest negative surface charge, lowest peroxide value (PV), p-anisidine value (p-AV), free fatty acid (FFA) value, and total oxidation value (TOTOX). The use of CNC imparted beneficial effects on reducing lipid oxidation and enhancing the stability of palm-based O/W emulsions stabilised by SC.