Zein-calcium alginate dual-shell liquid-core beads for tailored starch digestibility: Structural design, functional performance, and mechanistic analysis.

A single calcium alginate shell has poor barrier against digestive enzymes, restricting starch protection and necessitating a more robust shell. To address this, 1% sodium alginate were immersed in 0.25-1% zein solutions to form a hydrophobic protective layer. Chromaticity analysis showed that the b⁎ value increased from 7.45 to 24.08 with the increase of zein concentration. SEM images and laser confocal microscopy observations the formation of a zein/calcium alginate double-layer shell on the starch granule surface. Additionally, as the zein concentration in the immersion solution increased from 0% to 0.75%, the structure and properties of the beads tended to be stable. The construction of the hydrophobic zein shell significantly increased the hardness, thermal stability (To, Tp, ΔH), and anti-swelling ability of the liquid-core beads. The in vitro digestion experiments showed that the k value decreased significantly from 0.0083 to 0.0042, and the RS content increased significantly from 42.43% to 59.41%.