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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]

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]

The purpose of the present study was to explore the antioxidant activity of organic extracts from Maillard reaction products (MRPs) of sea cucumber (Stichopus japonicus) gut hydrolysates (SCGHs). The SCGHs were obtained after treatment with neutrase, and they were then reacted with ribose at a mass ratio of 1:2, pH 8.0, and 95 °C for up to 12 h. The MRPs were extracted by methanol and ethanol. The methanol extracts of the MRPs had a higher UV absorbance, browning intensity, and fluorescence intensity than the crude MRPs. The scavenging capacities of methanol and ethanol extracts from MRPs in both 2′,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl radical (DPPH) assays increased significantly (p < 0.05). The methanol extracts were better than the ethanol extracts showing the reduced IC50 levels for ABTS and DPPH by 50% and 50%, respectively. The inhibitory activity for peroxidation of linoleic acid of MRPs was also enhanced in the methanol extracts of MRPs, but this was reduced in ethanol extracts. Moreover, HepG2 cell viability after exposure to the methanol extracts of MRPs was increased to 59.30 ± 0.43% compared with the SCGHs and MRPs, which was 3.97 times that of the H2O2-treated group. These results suggest that methanol extraction can improve the antioxidant activity of SCGHs-ribose MRPs and that the corresponding extracts can be potentially used as food antioxidants. [ABSTRACT FROM AUTHOR]

The proteolysis in muscle tissues of sea cucumber Stichopus japonicus (sjMTs) was characterized. The proteins from sjMTs were primarily myosin heavy chains (MHCs), paramyosin (Pm), and actin (Ac) having a molecular mass of approximately 200, 98, and 42 kDa, respectively. Based on SDS-PAGE analysis and quantification of trichloroacetic acid (TCA)-soluble peptides released, degradation of muscle proteins from sjMTs was favorable at pH 5 and 50°C. Proteolysis of MHCs was mostly inhibited by cysteine protease inhibitors, including trans-epoxysuccinyl-L-leucyl-amido (4-guanidino) butane (E-64) and antipain (AP). E-64 and AP completely inhibited the degradation of Pm and Ac, while iodoacetic acid showed a partially inhibitory effect. These results indicated that the proteolysis of sjMTs was mainly attributed to cysteine proteases. Avoidance of setting the tissues at 40-50°C and slightly acidic condition and inhibition of cysteine proteases are helpful for decreasing sea cucumber autolysis. [ABSTRACT FROM AUTHOR]

Scallop ( Patinopecten yessoensis) female gonad hydrolysates (SFGHs) were obtained by using neutrase. The resulting hydrolysates possessed DPPH radical scavenging activity, ferrous ion-chelating ability, and reducing power with IC or AC values of 9.44, 0.94, and 5.88 mg/mL, respectively. SFGHs contained nearly 80 % of fractions with molecular weight around 250-5000 Da, and antioxidant-related amino acid residues in SFGHs reached to more than 30 %. Six fractions were separated from SFGHs on a Sephadex G-25 column, and one of the fractions with the highest DPPH radical scavenging activity was further analyzed by ESI-MS/MS, and a tetrapeptide His-Met-Ser-Tyr (536 Da) and a pentapeptide Pro-Glu-Ala-Ser-Tyr (565 Da) were identified. Both peptides showed hydroxyl radical scavenging activities with IC values of 3.6 and 16.8 mM, respectively, by electron spin resonance method. These results imply that peptides derived from scallop female gonads are potent antioxidants and may be utilized as functional ingredients in food systems. [ABSTRACT FROM AUTHOR]