Plant-based nanoparticles for food systems: preparation strategies, pH-driven assembly, and emerging plant-to-nano processing

Plant-based nanoparticles are emerging as clean-label carriers and structuring agents for functional foods, and pH-driven assembly has become an important aqueous strategy for their fabrication. This review summarizes recent progress in pH-driven plant-based nanoparticles based on proteins, polysaccharides, and protein-polysaccharide complexes. It discusses their formation mechanisms, including pH-induced solubilization, biopolymer unfolding or ionization, bioactive nucleation during neutralization, and stabilization through hydrophobic interactions, hydrogen bonding, and electrostatic interactions. It also summarizes key nanoparticle characteristics, including particle size, surface charge, encapsulation efficiency, stability, and digestion behavior. These characteristics are further connected with functional food applications, including bioactive delivery, antimicrobial protection, colorant stabilization, texture modification, and real food matrix performance. In addition, this review discusses an emerging one-step "plant-to-nano" strategy that directly extracts bioactive compounds and biopolymers from raw plant materials and converts them into self-assembled nanoparticles. Overall, pH-driven plant-based nanoparticles offer a promising platform for sustainable functional food design.