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The effects of oxidation on protein digestion and transport in cooked abalone muscles were investigated using a combination of simulated digestion and everted-rat-gut-sac models for the first time. Boiling heat treatments caused protein oxidation in the abalone muscles, reflected by increases in the carbonyl group and disulfide bond contents, protein hydrophobicity and aggregation degree, as well as decreases in the free sulfhydryl group and amino acid contents. Protein oxidation significantly inhibited the degree of hydrolysis, digestion rate, and digestibility of the abalone muscles in the simulated digestion model. The results from the everted-rat-gut-sac model showed that amino acid and peptide transport levels from the digestion products of the cooked abalone muscles were lower than those of the uncooked samples. In contrast, the addition of antioxidants of bamboo leaves mitigated heat-treatment-induced protein oxidation, aggregation and increased hydrophobicity, and consequently improved abalone muscle protein digestibility and transport levels.

Lipid hydrolysis and oxidation occurred in Argopecten irradians adductor muscle during hot air drying. Using an in vivo imaging system, we found that antioxidants of bamboo leaves (AOB) could diffuse into the adductor muscle upon marinating. Both tea polyphenols (TP) and AOB efficiently retarded lipid oxidation but had a slight effect on lipid hydrolysis during drying process. The in situ antioxidant mechanisms of AOB as well as TP were revealed, including quenching of free radicals detected by electron spin resonance, chelating metal ions determined by confocal laser scanning microscopy and inhibiting lipoxygenase. Less than 8% of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in AOB and TP marinated adductor muscle were decreased compared to more than 28% decrease in control adductor muscle during the drying process. Overall, these natural antioxidants, TP and AOB, efficiently maintained high nutritive value of adductor muscle, especially, their lipid quality., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Sea urchin gonads have been demonstrated to contain major yolk protein (MYP), which can be hydrolyzed by enzymes to release biologically active peptides. The in silico analysis of the MYP sequence in the BIOPEP database showed the presence of fragments with antioxidant activity. The sequence was hydrolyzed by 21 kinds of proteases and 23 antioxidant peptides were obtained. Eight peptides, including Leu-Trp (LW), Arg-Trp (RW), Ala-Trp (AW), Thr-Trp (TW), Ala-Asp-Phe (ADF), Leu-Trp-Lys (LWK), Ser-Asp-Phe (SDF) and Leu-Tyr (LY), were screened and a score over 0.5 was obtained using PeptideRanker. The peptides LW, TW and LWK showed a stronger antioxidant capacity with IC50 values of 8.85, 9.59 and 9.62 mmol L-1, respectively, compared to that of glutathione (10.81 mmol L-1). Furthermore, AW, LW and LY showed Trolox equivalent antioxidant capacity (TEAC) values of 3.07, 1.87 and 1.52 mmol TE per mmol peptide, respectively. These results suggest that the MYP from sea urchin (S. nudus) gonads is a good source of antioxidant peptides with abundant tryptophan.

The objective of the present study was to improve the utilization of scallop (Chlamys farreri) byproducts by using Maillard reaction. Scallop mantle hydrolysates (SMHs) were prepared using neutrase then reacted with ribose. Thirty-four peptides were identified from SMHs by UPLC-Q-TOF-MS, and the abundance of Asp and Lys suggested the strong Maillard reactivity. The formation of Schiff's base as well as modification of amide I, II and III bands in Maillard reaction products (MRPs) was confirmed by ultraviolet-visible, fluorescence, and Fourier transform infrared spectroscopy. Thirty volatile compounds were produced by the reaction of SMHs with ribose. Moreover, MRPs with enhanced radical scavenging and anti-linoleic acid peroxidation activities over SMHs promoted the survival and reduced the DNA damage of HepG2 cells treated with hydrogen peroxide. These results suggest that SMHs-ribose MRPs can be potentially used as food antioxidant for suppressing of lipid oxidation or protecting of cell from oxidative damage., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Food-borne nanoparticles have received great attention because of their unique physicochemical properties and potential health risk. In this study, carbon dots (CDs) formed during one of the most important chemical reactions in the food processing field, the Maillard reaction from the model system including glucose and lysine, were investigated. The CDs purified from Maillard reaction products emitted a strong blue fluorescence under ultraviolet light with a fluorescent quantum yield of 16.30%. In addition, they were roughly spherical, with sizes of around 4.3 nm, and mainly composed of carbon, oxygen, hydrogen, and nitrogen. Their surface groups such as hydroxyl, amino, and carboxyl groups were found to possibly enable CDs to scavenge DPPH and hydroxyl radicals. Furthermore, the cytotoxicity assessment of CDs showed that they could readily enter HepG2 cells while causing negligible cell death at low concentration. However, high CDs concentrations were highly cytotoxic and led to cell death via interference of the glycolytic pathway.

Here, a novel decapeptide IVTNWDDMEK with Maillard reactivity derived from scallop Chlamys farreri mantle was identified. The structural characteristics and in vitro hepatoprotective effects of IVTNWDDMEK conjugated with ribose were further investigated. The changes in decapeptide structures were determined by ultraviolet–visible (UV–vis), Fourier transform infrared (FTIR), and atomic force microscopy (AFM), and the modification sites induced by Maillard reaction of IVTNWDDMEK and ribose were monitored by high performance liquid chromatography/tandem mass spectrometry (HPLC‐MS/MS). Maillard reaction products (MRPs) of IVTNWDDMEK‐ribose demonstrate hepatoprotective benefits through the suppression of DNA damage and apoptosis induced by oxidative stress in human HepG2 cells in addition to enhancing the antioxidant activities. Moreover, after treatment with decapeptide‐ribose MRPs, the activities of cellular antioxidative enzymes, such as catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH‐Px), and glutathione reductase (GSH‐Rx) were remarkably increased, while the content of malondialdehyde (MDA) was decreased compared with H2O2‐treated group, thereby enhancing the intracellular antioxidant defenses. These findings demonstrate the potential utilization of decapeptide IVTNWDDMEK‐ribose MRPs as food antioxidants to suppress oxidative damage. Practical Application: In recent years, several food‐derived bioactive peptides and their derivatives are regarded as good dietary antioxidants for reducing oxidative stress and improving liver function. Here, a novel Maillard reactive decapeptide IVTNWDDMEK, identified from scallop mantle hydrolysates by peptidomics in the previous study was synthesized. Then, the correlation between intercellular antioxidant activities and chemical structure changes of IVTNWDDMEK‐ribose Maillard reaction conjugates was further studied. The preferable hepatoprotective activities of decapeptide IVTNWDDMEK‐ribose MRPs indicated that these MRPs could be potentially utilized as food antioxidants or additives in the production of nutritional foods. [ABSTRACT FROM AUTHOR]

In order to improve the utilization of scallop byproducts, scallop female gonad hydrolysates (SFGHs) were prepared using alcalase and ribose at a mass ratio of 1:2 and pH 7.0 (95°C, up to 12 h) to develop heterogeneous Maillard-type antioxidant and flavor compounds. The formation of Schiff's base as well as modification of the amide bands in Maillard reaction products (MRPs) were investigated using ultraviolet–visible, fluorescence, and Fourier transform infrared spectroscopy. The significant decrease of amino acid residues explained the strong Maillard reactivity of SFGHs. MRPs with enhanced ABTS+ radical scavenging capacity over SFGHs promoted the survival of HepG2 cells treated with hydrogen peroxide. Moreover, 19 new volatile compounds were produced by the reaction of SFGHs with ribose. These results suggest that SFGHs–ribose MRPs can be potentially used as antioxidants with flavor properties. Abbreviations: SFGs: scallop female gonads; SFGHs: scallop female gonad hydrolysates; ABTS: 2ʹ2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid); BHT: butylated hydroxytoluene; Trolox: 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid; MRPs: Maillard reaction product; H2O2: hydrogen peroxide; HS-SPME/GC/MS: Headspace solid phase micro-extraction/gas chromatography/mass spectrometry. [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]

In the present study, the effects of operational parameters on adsorption and desorption capacity of polyhydroxylated 1,4-naphthoquinone (PHNQ) pigments on macroporous resin in static mode were evaluated. On this basis, a suitable operating condition was selected which recovered 83.96 ± 0.71 and 80.58 ± 1.48 % of PHNQ pigments from Glyptocidaris crenularis and Strongylocentrotus intermedius spines, respectively. Based on accurate molecular mass and ultraviolet-visible (UV-Vis) spectral data acquired by ultra-performance liquid chromatography hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer (UPLC Q-TOFMS), spinochrome E, spinochrome D and spinochrome B were tentatively identified in the pigment extract prepared from G. crenularis. In contrast, only spinochrome B was identified in the pigment extract from S. intermedius. Between the two extracts, the one from G. crenularis showed stronger DPPH radical scavenging ability and ferrous ion chelating capacity. In our opinion, the different PHNQ compounds existing in the two extracts resulted in the difference in antioxidant activity. [ABSTRACT FROM AUTHOR]

The stability of polyhydroxylated 1,4-naphthoquinone pigment recovered from sea urchin ( Strongylocentrotus nudus) spines was observed by spectrophotometer. When pH values changed from 2.0 to 10.0, the pigment showed colour variations. Meanwhile, pH values affected the stability of the pigment. After 24 h of storage, the pigment remained 95.64%, 79.68% and 46.15% of the initial absorbance at pH 3.0, 7.0 and 10.0, respectively. The pigment was prone to degrade on exposure to light. It remained 40.11% of the initial absorbance under natural light after 14 days of storage. Whereas the corresponding value in the dark was 65.14%. Degradation rate of the pigment increased with increasing temperature. The pigment remained 90.49% of the initial absorbance at 20 °C after 24 h of storage. However, the corresponding value decreased to 66.61% at 80 °C. Additives, including antioxidant, oxidising and reducing agents, and some metal ions all affected the stability of the pigment. [ABSTRACT FROM AUTHOR]

Oligopeptides were prepared from the guts of sea cucumber Stichopus japonicus by autolysis method. Optimum autolysis conditions for preparing oligopeptides from the guts of sea cucumber were determined by response surface methodology using a central composite rotatable design. The effects of two independent variables, namely temperature and pH, on the response of trichloroacetic acid-soluble oligopeptides (mg/g on dry basis) were investigated. Regression analysis indicated that more than 95 % of the variation could be explained by the fitted models. Temperature at 48.30 °C and pH at 4.43 were found to be the optimal conditions to obtain oligopeptides from the guts of sea cucumber. The autolysis hydrolysates prepared at the optimized conditions were further fractionated into four major fractions (I-IV) by size exclusion chromatography on a Sephadex G-15 column. Fraction IV, which exhibited the highest DPPH radical scavenging capacity, Fe-chelating ability and protective effect against hydroxyl radical-induced DNA damage, was then analyzed by ESI-MS for molecular mass determination and ESI-MS/MS for the characterization of peptides. Two tetrapeptides (Val-Thr-Pro-Tyr and Val-Leu-Leu-Tyr) and a hexapeptide (Val-Gly-Thr-Val-Glu-Met) were found to exhibit protective effects against hydroxyl radical-induced DNA damage. These results suggest that antioxidant oligopeptides derived from the guts of sea cucumber by autolysis method could be utilized for functional foods. [ABSTRACT FROM AUTHOR]

Abstract: Purple sea urchin (Strongylocentrotus nudus) gonad was treated separately with neutral protease, papain, pepsin and trypsin. The resultant hydrolysates were fractionated using a series of ultrafiltration membranes (molecular weight cut-offs of 10, 5, 3 and 1 kDa). Five fractions were prepared from each hydrolysate and the corresponding molecular weight ranges were below 10 kDa, 5–10 kDa, 3–5 kDa, 1–3 kDa and below 1 kDa. The peptide fractions were evaluated for antioxidant activity by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay and reducing power assay. Results indicated that all peptide fractions possessed DPPH radical scavenging capacity and reducing power in a dose-dependent manner. For all four hydrolysates, the below 1 kDa fractions exhibited the highest DPPH radical scavenging capacity. The below 1 kDa fractions prepared with neutral protease, papain and pepsin, and the 1–3 kDa fraction prepared with trypsin showed the highest reducing capacity among corresponding hydrolysates. [ABSTRACT FROM AUTHOR]

Yesso scallop (Patinopecten yessoensis) gonad is the main by-product during processing. Our previous studies found that its Alcalase hydrolysates can act as a worthy precursor for Maillard reaction in the presence of ribose. Basing on the understanding of the characteristics of scallop female gonad hydrolysates (SFGHs)-ribose Maillard reaction products (MRPs), it was further extracted by different organic reagents and then was subjected to an in vitro digestion. The effects of digestion on the antioxidant and antimicrobial capacities of organic extracts from SFGHs-ribose MRPs were determined. Results showed that the scavenging activities of ethanol and methanol extracts on both ABTS·+ and DPPH·+ increased significantly before digestion, where methanol extracts were better than that of ethanol. However, the ·OH scavenging and linoleic acid peroxidation inhibition activities of MRPs were reduced in both extracts. Interestingly, there was a significant increase in the ABTS·+, ·OH scavenging activities and peroxidation inhibition capacity for all samples following digestion except for DPPH·+ scavenging activity. MRPs-methanol extracts showed the highest antimicrobial effect against Escherichia coli (E. coli) than other samples. Moreover, the HepG2 cell viability of MRPs-methanol extracts after digestion was increased to 89.58 %, which was 1.49, 1.26 and 1.14 times higher than H 2 O 2 -treated, SFGHs and MRPs group, respectively. Therefore, it is suggested that methanol extraction can improve the antioxidant capacity of SFGHs-ribose MRPs during digestion, and the corresponding extracts can be utilized as food antioxidants. • Scallop female gonad hydrolysates (SFGHs) and ribose produced Maillard reaction products (MRPs). • SFGHs-ribose MRPs was further extracted by organic reagents and subjected to an in vitro digestion. • Methanol extracts during digestion can be used as antioxidants for suppressing of radical scavenging and lipid oxidation. • Methanol extraction can improve the antimicrobial capacity of SFGHs-ribose MRPs. • SFGHs-ribose MRPs methanol extracts reduced the cytotoxicity induced by H 2 O 2 in HepG2 cells during digestion. [ABSTRACT FROM AUTHOR]

Abstract: Scallop (Patinopecten yessoensis) and abalone (Haliotis discus hannai Ino) muscle were hydrolysed with commercially available food-grade proteases. The resulting hydrolysates showed DPPH and hydroxyl radicals scavenging abilities, reducing power, and ferrous ion chelating capacity. The antioxidant activities of hydrolysate of abalone foot muscle (HAFM) increased with increasing incubation time during the whole hydrolysis process in 180min. Whereas, the antioxidant activities of hydrolysate of scallop adductor muscle (HSAM) increased at initial stage and peaked after 25–30min of hydrolysis, and then gradually decreased thereafter. Compared with HAFM, HSAM with comparable hydrolysis time contained more free amino acids (FAA) and small-sized peptides (below 500Da), which may account for the differences in antioxidant activities versus hydrolysis time curves of the two hydrolysates. The above results indicate that limited hydrolysis of proteins can increase their antioxidant activity, whereas extensive hydrolysis can decrease it. [Copyright &y& Elsevier]

Abstract: Purple sea urchin (Strongylocentrotus nudus) spines were dissolved in HCl–ethanol-aqueous solution. The polyhydroxylated 1,4-naphthoquinone (PHNQ) pigments were condensed and purified by using macroporous resin in static adsorption mode. PHNQ in the extract were characterised rapidly by using an ultra-performance liquid chromatography (UPLC) coupled to hybrid quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOFMS). Six known compounds including spinochrome E, 2,7-dihydroxynaphthazarin, spinochrome B, spinochrome C, spinochrome A and echinochrome A, and two new compounds with molecular formula of aminopentahydroxynaphthoquinone and acetylaminotrihydroxynaphthoquinone were identified tentatively. The pigment extract was evaluated for antioxidant activity by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging capacity assay, Fe2+ chelating assay, reducing power assay, lipid peroxidation inhibition assay and tertiary-butyl hydroperoxide (t-BOOH)-induced macrophages protection assay. In all testing methods, the extract showed excellent activity, indicating the PHNQ from S. nudus spines are potential sources of natural antioxidants. [Copyright &y& Elsevier]

[Display omitted] • Texture deterioration occurred in ready-to-eat abalone muscles during storage. • Protein oxidation and degradation occurred in ready-to-eat abalone muscles. • Collagen connective proteins were more prone to oxidation and degradation. • Bloodletting retarded protein oxidation and degradation in abalone muscles. • Antioxidants inhibited protein oxidation, improving texture and protein quality. The purpose of this study is to investigate the mechanism of texture deterioration and nutrient loss in ready-to-eat (RTE) abalone muscles during storage and the effects of antioxidants (lactic acid, citric acid and 4-hexylresorcinol) and pro-oxidants (copper ions bound to hemocyanin in abalone blood). Results suggested that storage caused protein oxidation in RTE abalone muscles during storage, reflected by increases in carbonyl group and disulfide bond contents, as well as decreases in free sulfhydryl group and amino acid contents, which also contributed to nutrient loss. Meanwhile, oxidation led to the degradation of proteins, especially collagen connective proteins, which caused decline in water hold capacity of RTE abalone muscles, ultimately resulting in decreases in shear force and hardness. In addition, adding antioxidants and eliminating pro-oxidants (copper ions) through bloodletting effectively retarded protein oxidation and degradation during storage, which significantly prevented texture deterioration and nutrient loss. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effect of ultrasound and the antioxidants of bamboo leaves (AOB) on the quality of scallop were evaluated. • UAOB-350 was the best treatment conditions on the quality maintenance of scallop. • UAOB-350 treatment could effectively retard protein and lipid oxidation. • UAOB-350 treatment could inhibit bacterial growth and texture deterioration. • UAOB-350 treatment prolonged the shelf life of scallop adductor muscles by 2 days. The combined effects of ultrasound and the antioxidants of bamboo leaves (AOB) on the quality maintenance of the adductor muscle of scallops (AMSs) during cold storage was investigated. Ultrasound power at 350 W coupled with AOB solution (2% w/v) (UAOB-350) was applied to treat the AMSs according to Taylor diagram analysis. The microstructure, oxidative changes (lipid and protein oxidation), total numbers of colonies, total volatile basic nitrogen, and texture of the AMSs during 6 days of cold storage were analysed. The results indicated that UAOB-350 treatment could effectively retard protein and lipid oxidation and bacterial growth and maintain better microstructure and texture characteristics than AOB solution treatment alone, prolonging the shelf life of the AMSs by 2 days during storage at 4 °C. These results indicate that the UAOB-350 combination method has promising potential to maintain the quality and extend the shelf life of AMSs during cold storage. [ABSTRACT FROM AUTHOR]

Phospholipids (PLs), the main lipid component in marine shellfish, consist mainly of glycerophosphocholine (GPC) and glycerophosphoethanolamine (GPE). This work compared the oxidative susceptibility of GPC and GPE in dried shellfish during storage and also investigated the effects of natural phenolic antioxidant on such oxidative susceptibility. The content of four representative polyunsaturated fatty acids (C18:3 n-3, C20:4 n-6, C20:5 n-3, and C22:6 n-3) esterified onto GPC or GPE in dried scallop adductor muscle during storage at two temperatures were matched with first-order kinetic models, in order to ascertain the oxidation reaction rate constant (k). The results showed that GPE possessed greater oxidation rate than GPC during storage, and GPC could be more effectively protected by the antioxidants of bamboo leaves (AOB, polar polyphenolic antioxidants) compared with GPE. This study provides a practical method for accurate evaluation of oxidative susceptibility of different PL classes in complex food systems. • Differences in oxidative susceptibility between GPC and GPE was studied. • GPE had a greater oxidation rate than GPC in dried scallop during storage. • Polar polyphenolic antioxidant more effectively limited oxidation of GPC than GPE. • A method to evaluate oxidative susceptibilities of different PL classes was developed. [ABSTRACT FROM AUTHOR]