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A composite hydrogel composed of scallop (Patinopecten yessoensis) male gonad hydrolysates (SMGHs) and κ -carrageenan (KC) was fabricated with a designed microstructure to preserve curcumin (Cur) during the upper gastrointestinal tract (GIT). The presence of KC obviously increased the initial elastic moduli (8.2–761.8 Pa), shortened the relaxation time T 23 (517.37–420.10 ms) as well as caused the blue shift of the emission peak and quenched the intrinsic fluorescence of Cur in SMGHs/KC-Cur system, signifying the solid combination within SMGHs and KC. In addition, the red shift in O–H stretching bands and blue shift in amide I bands in SMGHs/KC-Cur further accentuated the involvement of hydrogen bonds and electrostatic interactions within SMGHs, KC and Cur. The disappearance of crystalline structures suggested the successful embedment of Cur in the hydrophobic core of SMGHs. Moreover, the microstructure of the hydrogels varied from heterogeneous with tattered large pore cavities and scattered patches to homogeneous distribution with dense mesh and solid network wall. These scenarios caused a more compact network of SMGHs/KC-Cur than SMGHs-Cur to protect Cur from releasing in simulated intestinal and simulated colonic phases with slower released rate, both of which had the final extent of Cur release exceeding 90%. Furthermore, cryo-SEM showed that the significant release of Cur from hydrogels in the simulated intestinal phase was due to SMGHs matrix erosion with even larger pore sizes, tattered network and thinner network wall. Therefore, it is suggested that SMGHs/KC hydrogels with biocompatibility and good tolerance to acid environment could be reliable and desirable soft materials to embed and deliver Cur to the colon, having potential applications in functional foods and biological therapeutic purposes. [Display omitted] - Enhancement of gel elasticity in SMGHs/KC confirmed a feasible Cur-loaded carrier. - Migration of water in SMGHs/KC to bound water direction supported the Cur embedment. - Compact and dense porous networks of SMGHs/KC contributed to the Cur embedment. - Better sustained release of Cur in SMGHs/KC promised the delivery of Cur in colon. [ABSTRACT FROM AUTHOR]

The purpose of this study was to construct calcium cross-linked gelatinized lotus rhizome starch (LRS)/sodium alginate (SA) hydrogel beads of adjustable quality and to reduce the digestibility of gelatinized starch. LRS was mixed with SA, gelatinized by heating and subsequently cross-linked with Ca2+ to form hydrogel beads. The digestibility of the gelatinized LRS could be adjusted by changing the dose of SA in the hydrogel beads. When the LRS/SA ratio was 4/6, the rapidly digested starch (RDS) content in the beads was reduced by 26.9% compared with gelatinized LRS alone, whereas the slowly digested starch (SDS) and resistant starch (RS) contents increased by 12.3-fold and 2.3-fold, respectively. In addition, the water distribution in the Ca2+-crosslinked LRS/SA hydrogel bead samples also showed an SA dose dependence. With increasing SA concentration, the ability of the hydrogel beads to immobilize water increased. The diffusion of Ca2+ into the interpenetrating polymer network that was prepared with gelatinized LRS and SA gradually resulted in gelation dominated by ion bonds, leading to the heterogeneous microstructure of the hydrogel beads, which also involved intermolecular hydrogen bond interactions. Overall, the present study suggested a strategy for developing novel LRS hydrogel bead systems for quality control and gelatinized starch digestibility downregulation by adjusting the SA dose, which provided insights for the innovation of personalized and convenient starchy products in the food industry. [Display omitted] • Gelatinized lotus rhizome starch (LRS) was used to construct hydrogel beads. • Ca 2+ -crosslinked LRS/sodium alginate (SA) beads formed interpenetrating network. • There are mainly hydrogen and ion bonds in the Ca 2+ -crosslinked LRS/SA bead. • Digestibility of the LRS/SA hydrogel beads were SA dose dependent. [ABSTRACT FROM AUTHOR]