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Abstract This article reported the gelation and microstructural properties of scallop male gonads hydrolysates (SMGHs) in the presence of κ-Carrageenan (κ-C) and treated or untreated with potassium chloride (KCl). The presence of κ-C significantly increased the elastic moduli (10.3–449.5 Pa) and melting temperature (32.7–46.7 °C) of SMGHs. The decrease in the relaxation time (T 21 , T 23) signified the strong binding between SMGHs and κ-C. The blue shift in the amide I and II peals coupled with a new band of 1159 cm−1 in SMGHs/κ-C further demonstrated the electrostatic interactions between SMGHs and κ-C. κ-C rose the percentage of β-sheets from 28.10% to 35.93% but at the expense of α-helix and β-turn fractions and highly ebbed the intrinsic fluorescence of SMGHs. Such scenarios resulted in a more compact network formation and flocculation of κ-C chains. The salt-treatment to κ-C promoted helical formation, however, presence of SMGHs created larger interstitial spaces in the κ-C network due to aggregates of SMGHs and decreased the overall gel strength. The outcome promises novel opportunities in the design and development of functional hydrogels based on protein and polysaccharide complexes for food, pharmaceutical and biomedical applications. Graphical abstract Image 1 • Synergistic effectongelation occursbetweenκ-carrageenan(κ-C)and SMGHs. • Synergistic effect of κ-C on SMGHs may be attributed to the water migration in gel system. • Positive patches of SMGHs and sulfate groups of κ-C entangle by electrostatic interaction. • κ-C-κ-C connections hold the entire networkwhile SMGHsentrapintothisnetwork. • SMGHs appear to create larger interstitial spaces inκC/KClnetwork decreasinggel strength. [ABSTRACT FROM AUTHOR]

The combination of scallop male gonads hydrolysates (SMGHs) and κ -carrageenan (KC) was applied for curcumin (Cur) embedment and preservation, the corresponding Cur retention rate as well as gelation and microstructural properties were investigated during storage subjected to various pH (8 and 6) and temperature (25 °C and 4 °C). SMGHs-based gels could well protect Cur from degradation during 4 °C storage, with retention rate ranging from 95% to 97% after 30 day storage. At 25 °C, Cur could still be well preserved in SMGHs-based gels under pH 6 with Cur retention rate above 90%, while pH 8 led to rapid Cur degradation to around 75%. In addition, at pH 8 and 25 °C, the gel strength of SMGHs-Cur deteriorated significantly while evidently enhanced in SMGHs/KC-Cur due to synergistic combination within SMGHs and KC in couple with dehydration effect. Moreover, the water migration and distribution of SMGHs-based Cur-loaded vehicles were relatively stable at 4 °C while revealed apparent deterioration at 25 °C during storage. Furthermore, the microstructures of SMGHs/KC-Cur gradually transformed from homogeneous network with dense and smooth pores to tattered network with large and fragmentary pores, especially at 25 °C, promoting more Cur degradation. This study demonstrated that SMGHs/KC-Cur exhibited better than SMGHs-Cur in Cur preservation, potentially performing as excellent and sustainable protein hydrolysate/polysaccharide soft materials in food and biomedical fields. [Display omitted] • Acidic and low temperature are favorable for Cur protection in SMGHs-based vehicles. • SMGHs/KC performs better Cur preservation than SMGHs above 98% at 4 °C after 30 day. • Enhanced gel strength of SMGHs/KC-Cur after pH 8, 4 °C storage is due to dehydration. • Water migration and distribution are stable at 4 °C while deteriorate at 25 °C. • Compact and dense porous networks of SMGHs/KC allow more Cur retention at 4 °C. [ABSTRACT FROM AUTHOR]

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]