A highly stable W/O emulsion stabilized by β-cyclodextrin-citrus pectin composite nanoparticles for probiotic...

Traditional water-in-oil (W/O) emulsions are widely used as probiotic encapsulation templates due to their simple structure, but their practical application is limited by inherent drawbacks including fragile interfacial films, inadequate protection, and poor storage stability. This study proposes a novel strategy to reinforce the W/O interface through molecular synergy between β-cyclodextrin (β-CD) and citrus pectin (CP). Structural characterization confirmed the formation of composite nanoparticles (β-CDPNP, 296.67 nm) driven by hydrogen bonding and hydrophobic interactions. Compared to the individual components, β-CDPNP exhibited a higher absolute zeta potential (-35.57 mV) and an optimal three-phase contact angle (100.11°), indicating enhanced interfacial adsorption and anchoring capability. In the system, β-CD partially encapsulates hydrophobic regions of pectin chains, while the long-chain pectin acts as a scaffold anchoring multiple β-CD molecules to form an extended network. The resulting emulsion stabilized by β-CDPNP showed a nanoscale droplet size (427.43 nm) and excellent kinetic stability. Microscopy and rheology confirmed that β-CDPNP accumulated at the interface, forming a dense layer and inducing an elastic-dominated gel network. The encapsulation system achieved an encapsulation efficiency of over 80% for Bifidobacterium longum, protected the probiotics during simulated digestion (with a final viability >83%), and maintained stable viability above 74% over 28 days of storage. This work provides an effective and straightforward strategy for developing robust probiotic encapsulation emulsions with significant industrial potential.