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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 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]

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 T23 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 (T1 and T2 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. [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]

Roes are the main byproducts during the processing of large yellow croaker (Pseudosciaena crocea) and have not been well utilized. Heat-induced gels were prepared by using P. crocea roe protein isolates (pcRPI), and the influence of pH on the gel properties was also investigated. pcRPI could not form a gel at pH 4–6 but showed gelation behaviors at pH 7–9. The pcRPI gels prepared at pH 8 had a lower gel point (84 °C), and their G ′ reached 535.4 Pa. Moreover, pcRPI gels formed at pH 8–9 had a more continuous network structure with a shorter T 2 relaxation time than those at other pH conditions. Additionally, vitellogenin and vitellogenin B and C in pcRPI easily formed protein complexes during heating. The hydrophobic interactions, which were the main force between protein molecules during heating, as shown by molecular dynamics simulation, also contributed to gel formation. pcRPI has the potential to be used as a novel hydrogel product in food and other fields. • The optimum pH of P. crocea roe protein isolates (pcRPI) to form gels was pH 8. • The water holding ability of pcRPI gels was enhanced as pH increased. • The pcRPI gels had smoother surface and continuous network structure at pH 8–9. • Hydrophobic interactions were the main forces in the formation of pcRPI gels. [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]

Gel properties of hydrogel-forming by Ala-Lys dipeptide (AK) and iota-carrageenan (ι-C) were investigated by rheological behavior, fourier transform infrared analysis, cryo-scanning electron microscopy, low field-NMR relaxometry and magnetic resonance imaging. Iota-carrageenan was changed from a liquid to a gel with the addition of AK, and the existence of AK significantly increased the storage modulus (G') of ι-C from 590.4 to 1077.8 Pa. In the ι-C/AK gel, the blue-shift of O H stretching and water deformation were observed, meanwhile, the presence of amide I band at 1682 cm−1 was observed. The network of ι-C/AK gel showed a dense honeycomb structure with flocculating continuous phase and rough entanglement morphology. After adding AK, the water free in the pores of ι-C entered the ι-C/AK gel matrix, and the binding capacity of bound water was enhanced. These scenarios proved that the AK as the cationic dipeptide could control the conversion of negatively charged ι-C from an original random structure to a helical structure due to electrostatic interactions and hydrogen bonds. This study provides a new opportunity for the peptides into carbohydrate-based gel matrices, which could provide insights for the further application of ι-C/AK gels in the fields of food industry, tissue engineering and drug delivery. • AK dipeptide enhanced the gel properties of iota-carrageenan. • Electrostatic interactions was the main force in AK/ ι-C gel. • The hydrogen bond stabilized the AK/ι-C gel structure. • AK induced regular and homogenous network structure in the ι-C gel. [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]

[Display omitted] • -Ca2+ and K+ binding to IC promotes gelation of AK/IC with dose-dependent manner. • -Different state of water in AK/IC could resist the salt interference. • -AK/IC mediated by salts appears well honeycomb structures and even denser under Ca2+. • -AK/IC mediated by salts exhibits highly aggregation and entanglement fibers chains. • -Hydrogen bonding combined electrostatic interactions govern the salt-mediated AK/IC. The gelation and microstructural behaviors of Ala-Lys dipeptide/iota-carrageenan (AK/IC) mediated by salts were investigated. Obviously, salt addition prominently exaggerated the synergistic gelation between AK and IC, with storage modulus (G') of AK/IC and IC increasing extensively from 1145 to 9516 Pa or 5919 Pa and from 615 to 9981 Pa or 4693 Pa at 0.1 Hz with 0.5 % CaCl 2 or KCl, respectively, in which CaCl 2 revealed superiority over KCl. Additionally, different states of water in AK/IC gels resisted salt interference. Moreover, a honeycomb structure with denser porous networks coupled with rough entanglement morphology of AK/IC was observed, in which the CaCl 2 -treated group exhibited even smaller pore sizes. The conformational changes of AK/IC induced by salts were reflected by the redshift of –OH groups in AK/IC, insinuating salt-mediated H-bonding in AK/IC. The blueshift of amide I bands and water deformation groups of AK/IC in comparison to AK and IC alone illustrated the electrostatic interactions between them. Furthermore, coordination interaction, hydrogen bonds and hydrophobic interactive were highlighted among IC, AK and CaCl 2 /KCl as reflected by molecular docking. [ABSTRACT FROM AUTHOR]