Morphology-regulated millet bran nanocellulose-zein nanoparticles complexes: stabilization of Pickering emulsions and β-carotene delivery

This study revealed how the morphology of millet bran nanocelluloses, including cellulose nanocrystals (MCNCs), cellulose nanofibrils (MCNFs), and cellulose nanospheres (MCNSs), regulated the complexation with zein nanoparticles (ZNPs), thereby influencing structure and emulsifying performance of the resulting complexes. Electrostatic attraction, hydrogen bonding, and hydrophobic interaction induced 'chain-bead-like' structures in MCNCs-ZNPs and MCNFs-ZNPs, while MCNSs-ZNPs exhibited a 'bead-bead-like' structure. The 'chain-bead-like' structures conferred better emulsifying ability, producing emulsions with smaller droplets, higher viscosity, and better stability due to dense continuous phase networks, while 'bead-bead-like' structure induced a looser network. Structural advantages also persisted during <i>in vitro</i> digestion of β-carotene-loaded emulsions. MCNCs-ZNPs emulsion preserved droplet integrity under gastric conditions and promoted lipid digestion in intestinal phase, achieving higher β-carotene chemical stability (27.83 %) and bioaccessibility (9.93 %) than MCNFs-ZNPs (21.15 % and 8.02 %) and MCNSs-ZNPs (20.87 % and 6.56 %). Overall, this work highlights morphology-regulated nanocellulose-ZNPs complexes as effective emulsifiers for improving emulsion stability and delivering β-carotene.