Calcium ions induced ι-carrageenan-based gel-coating deposited on zein nanoparticles for encapsulating the curcumin

Zein, curcumin (Cur), and ι-carrageenan (ιCar) were used to prepare core-shell biopolymer nanoparticles (Zein-Cur-ιCar). These nanoparticles consisted of a nutraceutical-loaded protein core (curcumin-loaded zein nanoparticles) and a gelled polysaccharide shell (calcium cross-linked ι-carrageenan). The size, charge, morphology, and interactions of the nanoparticles were characterized by dynamic light scattering, zeta-potential analysis, scanning electron microscopy, and Fourier Transform infrared analysis. Ionic bridging, electrostatic attraction, hydrogen bonding, and hydrophobic attraction were involved in particle formation. The high encapsulation efficiency (93.2%) and loading capacity (6.2%) indicated that curcumin was well encapsulated within nanoparticles with optimized compositions (zein:ι-carrageenan 100:40). These particles had relatively small diameters (351.8 nm) and effectively delayed the light and thermal degradation of curcumin. Moreover, the curcumin within the nanoparticles was released in a sustained manner under simulated gastrointestinal conditions, which may improve its oral bioavailability. In summary, calcium carrageenan-coated zein nanoparticles have potential for the encapsulation, protection, and controlled release of hydrophobic nutrients.