Exploring the role of the thick and dense calcium alginate shell on the anti-digestibility mechanism of corn starch/carboxymethyl cellulose/calcium alginate liquid-core beads prepared by reverse spherification

To delaying starch digestion, a novel type of corn starch/carboxymethyl cellulose/calcium alginate liquid-core beads (CS/CMC/CaCl₂-SA) was designed using reverse spherification for the first time. Differential scanning calorimetry (DSC) results showed that the liquid-core beads exhibited significantly higher onset temperature (T_o), peak temperature (T_p), and conclusion temperature (T_c) compared to the original starch (p < 0.05). Compared with unencapsulated starch (13.61 ± 1.65 g/g), the swelling power of liquid-core beads significantly decreased to 4.40 ± 0.11 g/g at 95 °C. In addition, the fast digestible starch (RDS) of the cooked liquid-core beads at 1.5% sodium alginate concentration (CS/CMC/CaCl₂-SA_1.5%) is only 8.76 ± 0.62%, which is markedly lower than that of cooked CS (81.02 ± 0.26%). Meanwhile, the CS/CMC/CaCl₂-SA_1.5% sample demonstrated the lowest hydrolysis rate and an estimated glycemic index estimated (eGI) value of 65.93, placing it within the medium eGI range. Scanning electron microscopy (SEM) revealed the thick and dense calcium alginate shell of CS/CMC/CaCl₂-SA liquid-core beads maintained their integrity throughout cooking and digestion. This feature prevented water molecules and amylase from penetrating the interior of the beads, resulting in liquid-core beads with strong thermal stability, resistance to swelling, and slowly digestion. The liquid-core beads prepared in this study offer promising prospects for the design and development of slow-digestible starch.