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

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%.