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

Nanocellulose (CNF) as a stabilizer for Pickering emulsions has been widely interested in food, cosmetics and pharmaceuticals. However, cellulose crystal types have been less studied on the emulsification properties of Pickering emulsions. In this study, three different crystalline nanocelluloses (CNF I, CNF II and CNF III) were investigated as stabilizers for Pickering emulsions. CNF I was prepared by TEMPO-mediated oxidation. CNF II and CNF III were obtained by immersing CNF I in sodium hydroxide and ethylenediamine, respectively. CNF I was a fibrous structure (L/D=95.29), while CNF II and CNF III appeared as ellipsoidal nanoparticles with a “Needle-like” structure. The aspect ratios-averaged were 21.86 and 44.05, respectively. Three types of CNF had lower zeta potentials (<-30.0 mV). However, Pickering emulsions stabilized by CNF II had smaller droplet sizes (D3, 2), approximately one times smaller droplet sizes of CNF I and CNF III. However, compared with CNF I and CNF III, Pickering emulsions prepared with CNF II had poor stability. It was shown that the crystal morphology of CNF was particularly important for the stability of Pickering emulsions compared to the morphologies of CNF themselves in this work. It is obvious that CNF I and CNF III tended to have better emulsification properties.