Comparison of cellulose and chitin nanofibers on Pickering emulsion stability—Investigation of size and surface wettability contribution

There is an increasing concern about developing biobased colloid particles for Pickering stabilization due to the environment-friendliness and health-safety needs. In this study, Pickering emulsions were formed by using TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidized cellulose nanofibers (TOCN) and chitin nanofibers prepared by TEMPO-mediated oxidation (TOChN) or partial deacetylation (DEChN). The physicochemical characterizations of Pickering emulsions demonstrated that the higher cellulose or chitin nanofiber concentrations, surface wettability, and zeta-potential, the higher effectiveness in Pickering stabilization. Specifically, even though DEChN was at a shorter size (with a length of 254 ± 72 nm) as compared to TOCN (with a length of 3050 ± 1832 nm), it showed an excellent stabilization effect on emulsions at the concentration of 0.6 wt% due to its higher affinity to soybean oil (water contact angle of 84.38 ± 0.08°) and large electrostatic repulsion between oil particles. Meanwhile, when the concentration was 0.6 wt%, long TOCN (water contact angle of 43.06 ± 0.08°) formed a three-dimensional network in the aqueous phase, which produced a superstable Pickering emulsion resulting from the limited moving of droplets. These results provided important information on the formulation of Pickering emulsions stabilized by polysaccharide nanofibers with suitable concentration, size and surface wettability.