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This study evaluated the gel and microstructure properties of scallop (Patinopecten yessoensis) male gonads hydrolysates (SMGHs) combined with xanthan gum (XG). SMGHs/XG hydrogel matrix properties and structures were elucidated via different analysis tools such as rheometry, LF-NMR, FTIR, AFM, and Cryo-SEM. The addition of XG significantly improved the rheological properties of SMGHs, as indicated by 3.1-fold G' and 1.3-fold melting temperature with increasing the XG dose to 5.6 mg/ml. The corresponding decrease in the T 23 relaxation time from 450.3 to 365.6 ms also signified the strong binding between SMGHs and XG. SMGHs/XG also had a higher proton density (T 1 and T 2 weighted images) due to the higher bound and free water content of the hybrid gel systems, respectively. Additionally, the blueshift in the amide I and II bands in SMGHs/XG further indicated stronger electrostatic interactions between SMGHs and XG. Such scenarios resulted in a well-distributed and compact network with a rougher surface of SMGHs/XG in comparison to pure SMGHs and XG, as assessed by AFM and SEM. These results suggest that SMGHs/XG gel could be a potential hybrid gel applied in the food industry. PRACTICAL APPLICATION: Scallop (Patinopecten yessoensis) male gonads are edible, but are usually discarded during processing of scallop adductor. Because of its rich nutrition and gelation properties, scallop male gonads have a potential role in developing marine source-protein as a functional food base. The SMGHs/XG binary gel would be potentially applied in delivery system in food and biological fields. Further study is undergoing to apply SMGHs/XG binary gel to embed bioactive compounds, such as curcumin and β-carotene., (© 2021 Institute of Food Technologists®.)

The electrostatic complex coacervation between scallop Patinopecten. yessoensis male gonad hydrolysates (SMGHs) and κ-carrageenan (κ-C) were monitored by using turbidimetry at various pH (1-12) and biopolymer mixing ratio (9:1-1:9). The pH c exhibited ratio-independent behavior, and pH φ1 , pH max exhibited ratio-dependent behavior, respectively. The decreasing ratio enhanced the gel strength of SMGHs/κ-C at higher pH while inversely at lower pH, ascribing to more SMGHs aggregates and stronger neutralization between positively charged patches in SMGHs and κ-C at lower pH and higher ratio. Moreover, SMGHs/κ-C gel at acid condition exhibited lower relaxation times (T 21 and T 23 ). Furthermore, the rheological and relaxation time T 2 data were well associated with microscopy images which indicated that SMGHs/κ-C gel showed a well-distributed network structure at more acidic domains, supporting stronger gel rigidity and water-holding capacity., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Sea urchin Mesocentrotus nudus, Glyptocidaris crenularis, and Strongylocentrotus intermedius gonad protein isolates (mnGPIs, gcGPIs, and siGPIs) were extracted by isoelectric solubilization/precipitation (ISP) from the defatted gonads, and their functional properties were compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis results showed the similar protein pattern between each protein isolate and defatted gonad, indicating the high efficiency of ISP processing for protein recovery. Amino acid profileconfirmed that the mnGPIs and siGPIs could be potential sources of essential amino acid in nature. As regard to functional properties, mnGPIs showed higher water- and oil- holding capacities followed bysiGPIs and gcGPIs and all protein isolates presented great foaming property. As for emulsifying activity index (EAI), mnGPIs, gcGPIs, and siGPIs showed the minimum solubility and EAI at pH 5, 3, and 4, respectively, and behaved a pH-dependent manner. The gcGPIs revealed the highest EAI from pH 6 to 8 among the samples. In addition, circular dichroism showed increased content of β-sheet at the expense of α-helix and β-turn, suggesting the structure denaturation of the protein isolates. Indeed, no statistical difference was observed between secondary structure of mnGPIs and siGPIs. Moreover, ISP processing increased free sulfhydryl content of sea urchin protein isolates, but no difference was observed among the samples. Furthermore, siGPIs revealed the highest amount of total sulfhydryl and disulfide bonds, whereas both defatted gonads and protein isolates from G. crenularis presented the maximum surface hydrophobicity. These results suggest that gonad protein isolates from three species of sea urchin possess various functionalities and therefore can be potentially applied in food system. PRACTICAL APPLICATION: Sea urchin M. nudus, G. crenularis, and S. intermedius gonads are edible, whereas the functional properties of protein isolates from sea urchin gonad remain unknown. In this case, the extraction and comparison of three species of sea urchin gonad protein isolates will not only confirm functional properties but also screen food ingredients with suitable functions. In this study, functionalities of protein isolates derived from M. nudus, G. crenularis, and S. intermedius gonads would provide potential application in bakery food and meat products or as emulsifier candidates in food system., (© 2020 Institute of Food Technologists®.)

Involvement of DNA in gelation and microstructural properties of scallop ( Patinopecten yessoensis ) male gonad hydrolysates (SMGHs) and corresponding hybrid gel with κ-carrageenan (SMGHs/κ-C) was studied using DNase pretreatment. Although DNase pretreatment significantly transformed SMGHs from weak gels to liquid, it made SMGHs have a superior synergistic effect on gel formation with κ-C by evidence of 2.7-fold G ' and 1.1-fold melting temperature. However, the relaxation time ( T 21 and T 23 ), functional groups, and flocculation behavior were comparable between SMGHs/κ-C and SMGHs/DNase/κ-C. Moreover, SMGHs/DNase/κ-C exhibited a denser network with more numerous patches and larger void spaces. These results suggest that DNA contributes to the gel formation of SMGHs whereas restricts more cationic peptides in SMGHs to bind sulfate groups in κ-C during gel formation.

Protein isolates were recovered from scallop (Patinopecten yessoensis) gonads to develop a novel functional matrix by investigating their physiochemical and functional properties. Scallop gonad protein isolates (SGPIs) were prepared from degreased scallop gonads (DSGs) by an alkali extraction and isoelectric solubilization/precipitation (ISP) process. The protein compositions of the SGPIs were mainly vitellogenin and beta-actin with molecular weights of 266 and 42 kDa, respectively, as determined using Nano-liquid chromatography-mass/mass (Nano-LC-MS/MS). After the ISP process, the protein solubility of the SGPIs was significantly improved, and the surface hydrophobicity of SGPIs intensely increased by 1.1-fold, which were attributed to the exposure of aromatic residues such as phenylalanine, tyrosine, and tryptophan. However, the content of total/reactive sulfhydryl in SGPIs was decreased compared with that of DSGs. Meanwhile, the ISP process caused partial protein unfolding, as indicated by circular dichroism analysis, which exhibited a remarkable rise in the β-sheet content with a parallel decline in the α-helix and random coil contents (P < 0.05). SGPIs exhibited a better oil absorption capacity and foaming property than both DSGs and soybean protein isolates (SPIs). Moreover, the emulsifying capacity of SGPIs was greatly enhanced by the ISP process, which was superior to the effect of commercial SPIs and was ascribed to its favorable solubility as well as surface characteristics. PRACTICAL APPLICATION: During the processing of scallop (Patinopecten yessoensis) adductors, scallop gonad, a high-protein part, is usually discarded as processing by-products despite its edibility. In recent years, scallop gonads are regarded as good sources to develop protein matrices due to their high protein content and numerous nutrients. In this study, scallop gonad protein isolates (SGPIs) were isolated by isoelectric solubilization/precipitation (ISP) process. The preferable solubility, foaming property coupled with high emulsifying property of SGPIs indicated that the SGPIs could be potentially utilized as a good protein emulsifier and additives in production of kamaboko gels, hamburger patties, sausages, and pet foods., (© 2019 Institute of Food Technologists®.)

The gel properties and microstructure of scallop male gonad hydrolysates (SMGHs) were investigated by combing with κ‐carrageenan (κ‐C) and locust bean gum (LBG). It was shown that the initial elastic module of SMGHs/κ‐C 0.1 Hz got marked improvement from 202.3 Pa to 326.7 Pa and the melting temperature also increased 6°C with the addition of LBG. According to the data of low‐field nuclear magnetic resonance, the relaxation time T23 markedly reduced in SMGHs/κ‐C/LBG, representing the migration of water might result in a strong bind among SMGHs, κ‐C, and LBG. Fourier transform infrared spectroscopy showed the existence of hydrogen bonding between LBG and SMGHs/κ‐C. Low‐temperature scanning electron microscopy showed that the SMGHs/κ‐C/LBG ternary complexes possessed smaller voids and more dense network structures. These results could provide more possibilities for the application of SMGHs and polysaccharide complexes in functional hydrogel development. Novelty impact statement: We evaluated the gel and microstructure properties of ternary composite gel consisted of protein hydrolysates from male gonad of scallop (Patinopecten yessoensis) (SMGHs), κ‐carrageenan (κ‐C), and locust bean gum (LBG). The results showed that the addition of κ‐C and LBG significantly improved the gel properties of SMGHs. [ABSTRACT FROM AUTHOR]

The gel properties of scallop (Patinopecten yessoensis) male gonad hydrolysates (SMGHs) combined with different concentrations of iota-carrageenan (ι-C) were studied. SMGHs at 5% (w/v) were dispersed in 0.26%, 0.56% and 1.25% ι-C solution, respectively. The storage modulus value of SMGHs/ι-C increased with the increasing of ι-C concentration and reached 1392.7 Pa for 1.25% ι-C at 0.1 Hz, which was almost 116-fold greater than that of SMGHs. SMGHs combined with different concentrations of ι-C exhibited thermoreversible gel properties with melting and gelling temperatures of 40.2–51.3 °C and 30.6–33.9 °C, respectively. Non-destructive testing of gel samples by low-field nuclear magnetic resonance showed that the degree of water trapping in SMGHs/ι-C was in a ι-C concentration-dependent manner. SMGHs/ι-C showed three-dimensional network structures with a tendency toward denser with increasing of ι-C concentration. The improved gelation by the combination of SMGHs and ι-C as well as controlling the concentration of ι-C can provide information for potential application in food formulation. [ABSTRACT FROM AUTHOR]

The complex coacervation between scallop (Patinopecten yessoensis) female gonad protein isolates (SFGPIs) and sodium alginate (SA) was determined by the turbidimetric method. The impact of pH, total biopolymer concentration, biopolymer blend ratio, and various salt ionic on the mechanisms governing the complex coacervation of SFGPIs–SA complexes were also investigated. For the SFGPIs:SA ratio of 2:1 without adding NaCl, insoluble and soluble complexes were observed at pH 5.8 (pHφ1) and pH 8.2 (pHc) with the optimum biopolymer interactions appearing at pH 2.6 (pHopt). The maximum turbidity value increased with the increment of the total biopolymer concentration from 0.37 to 1.83 until attaining the critical value (0.75%). As the blend ratios rose from 1:3 to 12:1, the critical pH values (pHc, pHφ1, and pHopt) moved to higher pH. Furthermore, the addition of NaCl led to a remarkable decrease in turbidity over the whole pH region in SFGPIs–SA complexes. Moreover, monovalent ions (Na+ and K+) had the same effect on the formation of the SFGPIs–SA complex, whereas the divalent cations (Mg2+ and Ca2+) lessened the complex formation in comparison with the monovalent ions. This study offers a methodological and theoretical basis for the design of complex SFGPIs–SA systems by understanding the complex coacervation under different conditions. Practical Application: In recent years, several protein–polysaccharides complexes have been widely applied in food and biological systems. Scallop (Patinopecten yessoensis) female gonads are deemed as good marine sources for developing protein matrices on account of their high protein content and nutrients. In our study, the effects of different conditions on the mechanisms governing the complex coacervation of SFGPI–SA mixtures were investigated, and the instability of the system could be overcome by understanding the conditions for SFGPIs/SA complex formation, which have a feasible role in developing marine source‐protein as a functional food base such as kamaboko gels, can, sausage, fat substitutes, and delivery vehicles for bioactive compounds. [ABSTRACT FROM AUTHOR]

Natural polymeric proteins, isolated from scallop gonad, had already shown promise as a potent nutraceutical. The purpose of this study was to fabricate scallop gonad protein isolates (SGPIs) as a natural alternative emulsifier designed for improving the physicochemical stability of β-carotene (BC). The influence of carrier oil, including long- and medium-chain triglycerides (LCT/MCT), on the physicochemical stability of BC emulsions was investigated. The SGPI-stabilized BC emulsions were characterized in terms of viscosity, particle diameter, zeta-potential, atomic force microscopy (AFM), cryogenic scanning electron microscopy (cryo-SEM), and confocal laser scanning microscopy (CLSM). Compared to SGPI-MCT emulsions, SGPI-LCT emulsions had better resistance to high ionic strengths and thermal treatment. During the 30-day storage period, the particle diameter, zeta-potential, and BC degradation of both emulsions had a great change at 37 °C than at 25 or 4 °C, and the variation of SGPI-MCT emulsions was more obvious than that of SGPI-LCT, which could be attributed to the high viscosity of SGPI-LCT emulsions. These results indicate that SGPIs can be applied in protecting lipophilic bioactives by using emulsion-based systems, in which LCT oil was more effective for encapsulating and protecting BC than MCT oil. [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]

• 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]

Studying the noncovalent interactions between proteins and polysaccharides is quite important mainly due to the wide number of applications such as developing pH-responsive complexes. Scallop Patinopecten yessoensis male gonad hydrolysates‑sodium alginate (SMGHs-SA) was investigated as noncovalent complexes at pH from 1 to 10. The critical pH values pH C (around 6) and pHφ (around 4) were independent of the SMGHs-SA ratio, indicating the formation of soluble and insoluble complexes. The pH response of SMGHs-SA complexes was evaluated by investigating the rheological behavior, moisture distribution, functional group change and microstructure. Compared to the co-soluble and soluble complexes phases, the SMGHs-SA complexes had a higher storage modulus and viscosity as well as a lower relaxation time (T 23) in the insoluble complexes phase (pHφ>3). Additionally, the amide I band and COO− stretching vibration peaks were redshifted and the amide A band vibration peaks were blueshifted by acidification. Electrostatic interactions and intermolecular/intramolecular hydrogen bonding led to SMGHs-SA agglomeration at pH 3, forming a uniform and dense gel network structure with strong gel strength and water-retention capacity. This study provides a theoretical and methodological basis for the design of novel pH-responsive complexes by studying SMGHs-SA complex coacervation. • Scallop gonad hydrolysates (SMGHs) and sodium alginate (SA) could coacervate. • Acidification promoted the formation of SMGHs-SA coacervations. • Electrostatic interactions were the main force for the SMGHs-SA complex at pH 3. • Hydrogen bonding also drove the interaction of SMGHs and SA. [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 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]