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The objective of this study was to investigate the properties of ternary composite gel of scallop (Patinopecten yessoensis) protein hydrolysates (SMGHs)/κ‐carrageenan (KC)/xanthan gum (XG). The rheological properties, moisture‐distribution, molecular structure, and microstructure of SMGNs/KC/XG gels were analyzed. The results showed that the G′ value, melting temperature, and water holding capacity of SMGHs/KC/XG were higher than those of SMGHs, SMGHs/KC, and SMGHs/XG. FTIR spectrum showed the generation of hydrogen bonds between SMGHs and KC/XG, and the carboxylic acid group of XG interacts with SMGHs. Moreover, the cryo‐SEM results showed that SMGHs/KC/XG exhibited a tighter, smoother, and more aggregated microstructure than those of SMGHs, SMGHs/KC, and SMGHs/XG. These results indicate that the gel and microstructural properties of SMGHs are significantly improved by addition of KC and XG, and SMGHs/KC/XG has potential to be used as functional hydrogels for food, pharmaceutical, and biomedical applications. Practical Application: Scallop (Patinopecten yessoensis) male gonads are rich in protein and usually regarded as byproducts during adductor processing. Because of its gelation properties, scallop male gonads have potential to be used as functional hydrogels for food. The SMGHs/KC/XG ternary composite gel showed excellent gel properties, which would be potentially applied in delivery system in food and biological fields. Further study is undergoing to apply SMGHs/KC/XG to embed bioactive compounds, such as curcumin and β‐carotene. [ABSTRACT FROM AUTHOR]

Various bond disrupting agents including NaCl, GuHCl, urea, and SDS were introduced to investigate the intermolecular interactions between scallop (Patinopecten yessoensis) male gonad hydrolysates (SMGHs) and κ‐carrageenan (κ‐C), which were monitored by changes in rheological property, water distribution, conformation characterization and microstructure by using rheometer, low field‐NMR relaxometry, Fourier transform infrared (FTIR) spectroscopy, cryo‐scanning electron microscopy (cryo‐SEM), and confocal laser scanning microscopy. The results showed that the bond disrupting agents deteriorated the rheological property of SMGHs/κ‐C in a dose‐dependent manner. Indeed, at the same concentration of 2 M, NaCl deteriorated the SMGHs/κ‐C more obviously than GuHCl and urea. In addition, SMGHs/κ‐C with bond disrupting agents possessed higher relaxation times including T21 and T23, indicating the migration to free water direction of bound and free water. Moreover, the FITR results showed the red‐shift in water regions (amide A and B bands), amide I and II bands, and indicated the breakdown of hydrogen bonds and electrostatic interactions, indicating a disordered structure in SMGHs/κ‐C by various bond disrupting agents. Furthermore, cryo‐SEM results showed the change of SMGHs/κ‐C from a homogeneous network to a looser and ruptured one with larger void spaces, and indicated the disrupted and tattered microstructure of SMGHs/κ‐C by various bond disrupting agents. Additionally, SMGHs/κ‐C as well showed less aggregates stained by RITC by bond disrupting agents. These results suggest that electrostatic interactions would be mainly involved in the maintenance of SMGHs/κ‐C gel network. This study could provide theoretical and methodological basis for hydrogel products with modified gel strength and microstructure by understanding the intermolecular interactions in gel system. Practical Application: Scallop (Patinopecten yessoensis) male gonads as a high‐protein part of scallop, is usually discarded during processing despite its edibility. In recent years, scallop male gonads are regarded as good sources to develop protein matrices due to their high protein content and numerous nutrients. In this study, scallop male gonad hydrolysates (SMGHs) were obtained by trypsin‐treated process. The considerable gelation behavior of SMGHs indicated that the SMGHs could be potentially utilized as a novel thickener and additive in production of kamaboko gels, can, sausage and spread with marine flavor. [ABSTRACT FROM AUTHOR]

• Low-acyl gellan gum had effect on gelation of scallop male gonad hydrolysates (SMGHs). • Gel strength of SMGHs was increased with increasing of low-acyl gellan gum (GG) dose. • The thermal stability of SMGHs gel was improved by the addition of GG. • The promoting effect of GG on SMGHs gel was related to the water migration. • The SMGHs/GG composite gels showed a regular and homogenous network. This study aimed to examine the gelation and microstructural properties of scallop male gonad hydrolysates (SMGHs) in the presence of low-acyl gellan gum (GG) at different mass ratios. The rheological results showed that both elastic modulus and thermal stability of SMGHs were significantly improved by the addition of GG. Meanwhile, the relaxation time T 23 was significantly reduced in SMGHs/GG by low-field nuclear magnetic resonance, indicating a strong interaction between SMGHs and GG. Fourier transform infrared spectroscopy indicated the blueshift of amide I and II peaks in SMGHs/GG further demonstrated the electrostatic interaction between SMGHs and GG. The network structure of SMGHs/GG binary complexes was more compact and the surface was smoother than that of SMGHs by cryo-scanning electron microscopy. Furthermore, increasing the content of GG in the SMGHs/GG binary complex significantly reinforced the gel strength and promoted the gelation process. [ABSTRACT FROM AUTHOR]

The purpose of this study was to characterize the electrostatic complexation between scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and κ -carrageenan/xanthan gum (KC/XG) within pH 12–1 at different hydrolysate/polysaccharide ratios (9:1–1:9) and to investigate the influence of pH and ratios on gelation and microstructural properties for widening the application of marine-derived source. According to the phase diagram of SMGHs/KC/XG, pH c hold a constant value around pH 8.5, pH φ1 gradually shifted from 4.2 to 2.8, and pH max fluctuated within 2.4-1.4 as ratios decreasing from 9:1–2:8. Additionally, SMGHs/KC/XG showed higher gel strength in acid condition, as decreasing pH promoted the electrostatic attractive interactions within positively charged patches in SMGHs and negatively charged sulfate and carboxyl groups in KC/XG causing more tightly packed structures formation. Moreover, decreasing ratios from 9:1 to 3:7 could further enhance the gel strength of SMGHs/KC/XG, ascribing to the stronger gelation ability of polysaccharides and enough neutralization. Moreover, SMGHs/KC/XG exhibited well-organized microstructures with smaller pore sizes, denser and more homogeneous networks at more acid domains, supporting stronger gel strength. Therefore, this study provides theoretical and methodological basis for designing novel SMGHs/KC/XG hydrogels with considerable gel strength and microstructures through understanding the complex coacervation at different pH and ratios. • pH and ratio largely regulate turbidity changes of SMGHs/KC/XG complexes. • pH c exhibits ratio-independent, and pH φ1 , pH max exhibit ratio-dependent behaviors. • Higher KC/XG proportion supports stronger gel strength in soluble phases. • More SMGHs/KC/XG neutralization promotes gel formation in insoluble coacervate phase. • SMGHs/KC/XG exhibits well-organized and compact networks at acid condition. [ABSTRACT FROM AUTHOR]

[Display omitted] • -KC hydrogel beads with more SMGHs can increase Cur load due to tight cross-linking. • -Modified FTIR and amorphous structure in SMGHs/KC/KCl prove successful Cur embedment. • -SMGHs/KC/KCl-Cur hydrogel beads have heterogeneous networks with backbone and voids. • -SMGHs/KC/KCl hydrogel beads perform as effective colon-targeting Cur delivery system. • -SMGHs/KC/KCl hydrogel beads promise Cur preservation above 90% during 30 day at 4 °C. Scallop (Patinopecten yessoensis) male gonad hydrolysates (SMGHs)/ κ -carrageenan (KC)/KCl beads with SMGHs:KC ratios (0:10–5:5) were investigated. SMGHs/KC/KCl-Cur bead (5:5) exhibited the most intact spherical morphology and highest Cur loading content of 0.063 mg/0.1 g bead, ascribing to a shortened T 23 from 1607.9 to 966.4 ms, and red and blueshifts of O H, NH, amide I and II bands. The undetected fingerprint region within 7.82°-28.90° of SMGHs/KC/KCl-Cur beads indicated successful Cur entrapment. Moreover, SMGHs/KC/KCl-Cur beads exhibited shrinkage network backbones and larger void pores as SMGHs increased, with vessel percentage area, total number of junctions, total vessel length decreasing from 52.1, 1446.8, 57931.4 to 39.7, 530.5, 34458.4, and lacunarity increasing from 0.048 to 0.111, respectively. Furthermore, Cur showed approximately 50% release contents in colon phase and above 90% retention rate during 30 days of storage at 4 °C. These results suggested that SMGHs/KC/KCl-Cur beads exhibited sustained-release of Cur and promised stable Cur preservation. [ABSTRACT FROM AUTHOR]

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]

Abstract In order to provide a foundation for comprehensive utilization of scallop (Patinopecten yessoensis) , the gel properties of hydrolysates from scallop male gonad (SMGHs) were studied. The hydrolysates were obtained from scallop male gonads (SMGs) by using trypsin. The changes in molecular mass of proteins were determined by SDS-PAGE and HPLC with a peptide separation column. The gel properties of SMGHs were investigated by using rheometer and texture instrument in comparison with that of ι-carrageenan and gelatin. The results showed that the proteins of SMGs were significantly degraded after hydrolysis with trypsin at a dosage of 3000 U/g protein. The SMGHs showed an appearance of gelation after hydrolysis for 30–180 min and cooling down. Under various sweep models, the values of storage modulus (G′), loss modulus (G″), viscosity (ƞ) of SMGHs were obvious higher than those of SMGs. The textural parameters containing firmness, cohesiveness and adhesive force of SMGHs at dosages of 50 and 75 mg/mL were similar to those of ι-carrageenan and gelatin at 25 mg/mL, respectively. For the mixtures, the gel property of SMGHs/ι-carrageenan SMGHs/gelatin increased significantly. The low-field NMR (LF-NMR) also reflected the T 23 of SMGHs/ι-carrageenan, T 21 of SMGHs/ι-carrageenan and SMGHs/gelatin mixture decreased significantly in comparison with SMGHs alone. These results suggest that SMGHs could be applied as a potential gelling and thickening agent in food formulations. Graphical abstract Image 1 Highlights • SMGHs treated by trypsin showed a specific gel property caused by peptides. • Gel property of SMGHs had hydrolysate time- and hydrolysate dose-dependent manners. • Gel strength of SMGHscan be comparable with ι-carrageenan and gelatin. • Synergistic effect on gelation was occurred betweenι-carrageenanand SMGHs. • Synergistic effect on water migration was foundbetweenι-carrageenanand SMGHs. [ABSTRACT FROM AUTHOR]

• Complex coacervation of SMGHs/ κ -C is largely governed by NaCl/KCl. • pH c and pH φ1 exhibited salt-dependent behaviors. • Optical density of SMGHs/ κ -C was regulated by salt-enhanced and -reduced effect. • Salt addition enhanced SMGHs/ κ -C gels mainly driven by electrostatic forces. • SMGHs/ κ -C showed more flocculation, larger pore and thicker network wall with salt. The complex coacervation between scallop Patinopecten yessoensis male gonad hydrolysates (SMGHs) and κ -carrageenan (κ -C) as influenced by ionic strength (NaCl and KCl) were monitored by using turbidimetric analysis at pH 1–12. The optical density of SMGHs/ κ -C complexes initially increased at lower ionic strength (0–0.5 M) whereas decreased at higher ionic strength (0.5–1.5 M) as a result of the salt-enhanced and salt-reduced effect, respectively. Both of pH c and pH φ1 exhibited ionic strength-dependent behavior that firstly shifted to acidic pH followed by an increase as salt increasing. Moreover, salt addition strongly promoted the gelation of SMGHs/ κ -C which was mainly driven by electrostatic forces, as reflected by increasing storage modulus G' from 3621 to 6559 Pa, 2681–25631 Pa at 0.1 Hz and decreasing T 23 relaxation time from 349.10 to 296.89 ms, 241.07–186.89 ms by 0–0.5 M NaCl/KCl, respectively. Furthermore, the rheological and relaxation time T 2 data were well associated with microscopy images that SMGHs/ κ -C gels with NaCl/KCl showed a denser network with more flocculation formation and larger pore sizes with thicker network wall, especially in KCl group, which indeed supported the gel elasticity. Taken together, this study could provide theoretical and methodological basis for new functional hydrogel products with modified gel strength and microstructure by understanding the complex coacervation in gel system. [ABSTRACT FROM AUTHOR]