Sunflower stem pith cellulose with different allomorphic nanocrystals for oil-in-water emulsions

Pickering emulsions utilize colloidal particles as stabilizers instead of traditional surfactants, offering the advantages of low dosage and high stability, and cellulose nanofibers (CNF) as a stabilizer for Pickering emulsions has been widely attracted by food, cosmetics and pharmaceuticals. However, the emulsification properties of CNF are affected by the crystalline form and length-diameter ratio of CNF. In this work, we investigate the stabilizer effect of different cellulose crystal types (CNF I, CNF II and CNF III) on Pickering emulsions. CNF I was a fibrous structure (Length/Diameter = 95.3), while CNF II and CNF III appeared as ellipsoidal nanoparticles with a "Needle-like" structure, and the aspect ratios of CNF II and CNF III averaged were 11.3 and 44.1. CNF I with high length-diameter ratio exhibited better emulsification properties. Meanwhile, Pickering emulsions stabilized by CNF II exhibited significantly smaller droplet sizes (D_{3, 2}), approximately one time smaller than those stabilized by CNF I and CNF III. However, when the emulsions were left to stand for 14 days, the cellulose-stabilized emulsions were significantly not as good as the emulsions stabilized by CNF I and CNF III, probably due to the lower absolute value of zeta potential of CNF II. Overall, the Pickering emulsions prepared with CNF II were less favorable when compared to those stabilized by CNF I and CNF III. This comparative investigation advances fundamental understanding of cellulose-mediated Pickering stabilization mechanisms and facilitates targeted applications in emulsion-based formulations across multiple industrial sectors.