Silver Carp Protein Research Articles

Effect of konjac oligosaccharide and Kappa-Carrageenan on oxidative and structural changes in silver carp protein induced by fluctuating storage temperatures

ABSTRACT Two different low molecular cryoprotectants were analyzed in silver carp surimi proteins during different frozen storage conditions (FTC), and a comparison was performed with a conventional cryoprotectant mixture of sucrose (4%) and sorbitol (4%) as positive control (PC). The results showed that a significant decline was noted in sulfhydryl contents (SH), an increase in carbonyl groups, and a surface hydrophobicity due to myosin and protein oxidation. Meanwhile, FTC also altered the stability of secondary and tertiary structures due to the denaturative changes in myofibrillar proteins (MP). Meanwhile, samples that incorporated KC (3%), KOG (3%), and PC showed significant stability in MP against FTC induced changes. This is due to their strong hydrophilic and hydrogen interactions. MP samples containing KOG (3%) demonstrated improved cryoprotective abilities against oxidative and structural changes. Thus, we can recommend KOG as a potential cryoprotectant for maintaining the shelf-life of fish and related products on an industrial scale.

Plastein reaction enhances the emulsifying and rheological properties of silver carp hydrolysates in oil-in-water emulsions

The plastein reaction was ubiquitously acknowledged for its capacity to enhance the functional properties of protein hydrolysates. Despite this, the specific impact of the plastein reaction on emulsification, a critical functional aspect of protein hydrolysates, remains incompletely understood. In this study, the plastein reaction in silver carp protein hydrolysate (SCPH) was explored. A detailed comparison between the primary product (PP) and the blended product (SCPH–P) in terms of their oil-water interfacial adsorption kinetics and the shear strain of oil-in-water emulsions was reported. The interfacial adsorption kinetics suggested that the higher molecular weight imparted a slow rate of diffusion, penetration, and reorganization to the PP compared to SCPH-P. Furthermore, the elevated surface hydrophobicity also resulted in higher surface activity (i.e., high interfacial pressure) for PP. Simultaneously, nonlinear rheological analysis revealed that PP possessed enhanced resistance to shear strain due to its strong affinity for the oil-water interface of emulsion. These improvements manifested in PP-stabilized emulsions with reduced mean particle size (71.6 μm–9.5 μm), diminished instability index (nearly 3-fold prolongation of stabilization time), and increased electrostatic repulsion (zeta potential values increased from 6-15 mV to 21–27 mV), which underscored a substantial enhancement in the emulsification of SCPH through the plastein reaction. Notably, the emulsifying and rheological properties of PP at a 1% (w/w) concentration were nearly equivalent to those of soybean protein isolate at 0.5% (w/w), highlighting the plastein reaction's innovative potential in utilizing SCPH as a promising emulsifier.

Plastein reaction augments the metal chelating capabilities of silver carp (Hypophthalmichthys molitrix) hydrolysates: Unlocking the chemical modification mechanism

Plastein reaction mechanisms and the alteration of its product properties have been studied for decades. This study investigated the plastein-mediated modifications in silver carp protein hydrolysate (SCPH) from both mechanistic and functional perspectives. Unlike prior research, this investigation uncovered that hydrogen bonding supplemented the dominant hydrophobic interactions in plastein's mechanism for the first time, as supported by peptide concentrations, molecular weight, amino acids, chemical forces, and peptide sequence by LC-MS/MS. This innovative reaction mechanism cascaded into the enhancement of SCPH functional attributes. Plastein induced increased COOH in SCPH’s side-chain groups significantly enhanced Fe2+ (from 4.49 to 14.12 %) and Zn2+ (from 53.53 to 64.47 %) chelation. Moreover, the elevated DPPH (17.56 %–23.97 %) and hydroxyl radical (68.49 %–79.32 %) scavenging power indicated a broader improvement in SCPH with plastein. In SCPH, plastein elucidated reaction intricacies and enhanced its utility, propelling SCPH into a realm of extended potential.

Cryoprotective role of konjac oligosaccharide on silver carp proteins during frozen storage through molecular dynamic simulation

The cryoprotective effect of konjac oligosaccharide (KOG) on the silver carp surimi proteins during frozen storage was analyzed. Meanwhile, molecular dynamic simulation (MD) was carried out to examine the insight interaction of KOG with myosin. The Ca2+-ATPase and gel strength decreased in all samples, despite the treatment with a sucrose (4%) + sorbitol (4%) mixture as PC and KOG (1 and 3%). The samples added with no cryoprotectants (C) showed a remarkable decline in Ca2+-ATPase activity and gel strength. The decline in these properties could be due to oxidative changes in myosin, ice crystallization, and protein denaturation. Most interestingly, KOG (3%) incorporated samples that presented significant constancy in Ca2+-ATPase and gel strength properties, this stability was further proved with a MD computational study. Our findings of homology and MD analysis affirmed that KOG could substitute water molecules and form hydrogen bonds with amino acid residues, thereby leading to protein stability. Overall, the KOG water substitution action played an efficient cryoprotective effect on frozen silver carp protein. Furthermore, this application could extend the role of KOG at the industrial level as an effective cryoprotectant.

Gel Properties and Structural Characteristics of Composite Gels of Soy Protein Isolate and Silver Carp Protein.

Problems with silver carp protein (SCP) include a strong fishy odor, low gel strength of SCP surimi, and susceptibility to gel degradation. The objective of this study was to improve the gel quality of SCP. The effects of the addition of native soy protein isolate (SPI) and SPI subjected to papain-restricted hydrolysis on the gel characteristics and structural features of SCP were studied. The β-sheet structures in SPI increased after papain treatment. SPI treated with papain was crosslinked with SCP using glutamine transaminase (TG) to form a composite gel. Compared with the control, the addition of modified SPI increased the hardness, springiness, chewiness, cohesiveness, and water-holding capacity (WHC) of the protein gel (p < 0.05). In particular, the effects were most significant when the degree of SPI hydrolysis (DH) was 0.5% (i.e., gel sample M-2). The molecular force results demonstrated that hydrogen bonding, disulfide bonding, and hydrophobic association are important molecular forces in gel formation. The addition of the modified SPI increases the number of hydrogen bonds and the disulfide bonds. Scanning electron microscopy (SEM) analysis showed that the papain modifications allowed the formation of a composite gel with a complex, continuous, and uniform gel structure. However, the control of the DH is important as additional enzymatic hydrolysis of SPI decreased TG crosslinking. Overall, modified SPI has the potential to improve SCP gel texture and WHC.

Dual cryoprotective and antioxidant effects of silver carp (Hypophthalmichthys molitrix) protein hydrolysates on unwashed surimi stored at conventional and ultra-low frozen temperatures

The dual cryoprotective and antioxidant effects of silver carp hydrolysates on unwashed surimi, stored at conventional (−18 °C) or ultra-low (−60 °C) temperatures and subject to three and six freeze-thaw treatments, were examined. The addition of hydrolysates could alleviate the formation of carbonyls of myofibrillar protein, inhibit the decrease of free sulfhydryl content and keep the protein bands stability compared to the control and SuSo group. The lipid peroxidation product malondialdehyde, and the target volatiles hexanal, nonanal and 1-octen-3-ol of the unwashed surimi as detected by HS-SPME-GC-MS, increased slowly under the protection of hydrolysates. The oxidation for proteins and lipids in freeze-thawed samples stored at −18 °C are lower than those of samples stored at −60 °C (p < 0.05), indicating that ultra-low frozen temperature storage accompanied by freeze-thaw cycles accelerates structural deterioration of unwashed surimi. LF-NMR and SEM also revealed that the hydrolysates facilitated to form gel network with preferable structural integrity and stability during freeze-thaw treatments. This study provides theoretical supports for the application of silver carp protein hydrolysates as a cryoprotectant in transportation and storage of frozen surimi.

Purification and identification of novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport

Unregulated oxidative reactions occur in human body or food system can cause harmful effects both on food quality and human health. This study aimed to develop novel antioxidant peptides from silver carp muscle hydrolysate after simulated gastrointestinal digestion and transepithelial transport. Results showed that alcalase- and papain-induced hydrolysates had higher antioxidant activities before and after in vitro gastrointestinal digestion. Fractions with molecular weight <1 kDa from these two digestive products (named A-GID-1 and P-GID-1) exhibited the greatest antioxidant capacity, which was ascribed to the large proportion of low-molecular peptides and hydrophobic amino acids. After transepithelial transport analysis, a total of ten peptides were identified from the RP-HPLC fractions with the highest antioxidant activity from both P-GID-1 and A-GID-1 permeates. Among them, LVPVAVF exhibited the highest DPPH radical scavenging and reactive oxygen species (ROS) inhibitory activity. Our findings will provide new knowledge for the development of novel natural antioxidants and the high-value utilization of silver carp protein.

Sequential extraction of gel-forming proteins, collagen and collagen hydrolysate from gutted silver carp (Hypophthalmichthys molitrix), a biorefinery approach

Collagen and collagen hydrolysate (CH) was recovered from the bone and skin containing sediment residue emerging during pH-shift-based protein isolation from silver carp. Hydrolysis resulted in higher yield (15.1–15.4%) compared to collagen isolation by acid or pepsin (3.1–5.9%) (p<0.05). Isolated collagens were characterized as type I and maintained their triple-helical structure, confirmed by SDS-PAGE and FTIR. Pepsin-hydrolysis and sequential hydrolysis by pepsin and trypsin hydrolyzed all heavy molecular weight chains of collagen but sequential hydrolysis yielded higher degree of hydrolysis. When CH was added to a silver carp protein isolate prior to gelation, the gel behavior was dependent on molecular weight of the added CH. More hydrolyzed collagen emerging from sequential hydrolysis improved water holding capacity of the gel while reducing its breaking force. Thus, residue from pH-shift processing of fish can be used for isolation of high quality collagen/CH and provides a promising basis for a multiple-product fish biorefinery.

Evaluation of Plasticizing and Antioxidant Properties of Silver Carp Protein Hydrolysates in Fish Gelatin Film

ABSTRACTPhysico-mechanical and antioxidant properties of glycerol plasticized fish gelatin films were investigated at different levels of fish protein hydrolysates (FPH) from silver carp muscle (5, 10, 15, and 20 g FPH/100 g gelatin). The films supplemented with FPH, especially at higher concentration showed significant increase in 2, 2-diphenyl-1-picrylhydrazyl (DPPH), 2, 20-azinobis-(3-ethylbenzothiazoline-6-sulfnic acid) (ABTS) radical scavenging, and ferric reducing antioxidant power (FRAP), elongation at break, difference of color, water vapor permeability and opacity, while tensile strength, elastic modulus, L*, b*, and contact angle decreased markedly (p < 0.05). However, no significant differences were observed for a* and solubility of all samples (p > 0.05). Films prepared using 20% FPH had lower glass transition temperature and more homogeneous structure, compared with control film. Also, Fourier transform infrared (FTIR) spectroscopy confirmed the increase of free groups of hydrolysates and lower interaction between chains of film incorporated with the highest content of FPH. Thus, these results indicate that FPH enhanced the antioxidant activities and affected some characteristics due to less interaction between gelatin and FPH.

Dipeptidyl Peptidase IV-Inhibitory Peptides Derived from Silver Carp (Hypophthalmichthys molitrix Val.) Proteins.

The dipeptidyl peptidase IV (DPP-IV)-inhibitory bioactivity of silver carp protein (SCP) hydrolysates were investigated, and their containing efficacious DPP-IV-inhibitory peptides were explored by in silico hydrolysis analysis, peptide separation combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS) identification, and chemical synthesis. SCP hydrolysates generated by six proteases all showed efficient DPP-IV-inhibitory activities, and Neutrase-generated hydrolysates had the greatest DPP-IV inhibition (IC50 of 1.12 mg/mL). In silico Neutrase hydrolysis revealed hundreds of fragments released from myosin, actin, and collagen of SCPs, which include different Pro-motif peptides but only three reported peptidic DPP-IV inhibitors with moderate or weak bioactivity. In addition, three new DPP-IV-inhibitory peptides were identified using LC-MS/MS; in particular, LPIIDI and APGPAGP showed high DPP-IV-inhibitory activity with IC50 of 105.44 and 229.14 μM, respectively, and behaved in competitive/non-competitive mixed-type DPP-IV inhibition mode. The results indicate that the SCP-derived DPP-IV-inhibitory peptides could be potential functional ingredients in the diabetic diet.

Characterization and Cryoprotection of Invasive Silver Carp (Hypophthalmicthys molitrix) Protein Hydrolysates

ABSTRACTSilver carp (Hypophthalmicthys molitrix) is regarded as an invasive, underutilized freshwater fish causing environmental and economic complications along the U.S. Mississippi River System. In this study, silver carp protein hydrolysates (FPH) were obtained from 30, 60, 90, 120, and 240 min hydrolysis with Protamex®. Amino acid composition showed polar amino acids, including Asp and Glu, and freed hydrophobic residues in FPH-90 and FPH-240. Protein surface hydrophobicity of FPH increased with increasing degree of hydrolysis. Cryoprotection was evaluated using a muscle (mince) food system with 6% FPH (w/w) from each hydrolysis time condition, an untreated mince (CTRL), and 8% (w/w) 1:1 sucrose-sorbitol (SUSO), respectively. After six freeze-thaw cycles (D7), all FPH treatments had lower (p < 0.05) expressible moisture, indicating strong water-holding capacity by the FPH. FPH formulations also imparted antifreeze activity equal to or better than SUSO, with the FPH-90 exhibiting higher (p < 0.05) proportion (43.9%) of unfrozen water at D7. Results from this study provide preliminary evidence for development of effective cryoprotectants using an underutilized, invasive fish species that can be exploited for environmental and economic gain in the form of value-added ingredients and further provide opportunities to understand the fundamental physicochemical properties governing cryoprotection of FPH in a frozen mince system.

PH shift protein recovery with organic acids on texture and color of cooked gels

Isoelectric solubilization and precipitation (ISP) processing uses pH shifts to separate protein from fish frames, which may increase commercial interest for silver carp. Texture and color properties of gels made from silver carp protein recovered at different pH strategies and organic acid types were compared. ISP was applied to headed gutted silver carp using 10 mol L(-1) sodium hydroxide (NaOH) and either glacial acetic acid (AA) or a (1:1) formic and lactic acid combination (F&L). Protein gels were made with recovered protein and standard functional additives. Texture profile analysis and the Kramer shear test showed that protein gels made from protein solubilized at basic pH values were firmer, harder, more cohesive, gummier and chewier (P < 0.05) than proteins solubilized under acidic conditions. Acidic solubilization led to whiter (P < 0.05) gels, and using F&L during ISP yielded whiter gels under all treatments (P < 0.05). Gels made from ISP-recovered silver carp protein using organic acids show potential for use as a functional ingredient in restructured foods.

Assessing the Antioxidant Activity of the Ultrafiltration Fractions From Silver Carp Protein Hydrolysate by Different Antioxidant Methods

Silver carp protein hydrolysate (SH) was fractionated by 5- and 1-kDa cutoff ultrafiltration (UF) membrane, and three ultrafiltrates were obtained: SHI (>5 kDa), SHII (1–5 kDa), and SHIII (<1 kDa) which were screened for antioxidant activity by five in vitro assays. The SHIII showed higher 2, 2-azobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and oxygen radical absorbance capacity (ORAC) values, inhibiting effects for liposome oxidation induced by Fe3+/VC. The SHII showed higher ferric reducing power (FRAP) and inhibiting effects for liposome oxidation induced by 2, 2′-azobis (2-methylpropionamidine) dihydrochloride (AAPH). However, the SHI showed the highest 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radicals scavenging activity. Therefore, the antioxidant activity of silver carp protein hydrolysates was mainly associated with their molecular weight distribution, and the antioxidant assays used to test different samples gave comparable results.

Effect of substrate ratios and temperatures on development of Maillard reaction and antioxidant activity of silver carp (Hypophthalmichthys molitrix) protein hydrolysate-glucose system

The study of antioxidant activity of the hydrolysates is necessary during its processing in which Maillard reaction would often occur. To understand the effect of Maillard reaction on antioxidant activity of silver carp protein hydrolysates (SPH), the Maillard reaction products (MRPs) were prepared at different ratios between SPH and glucose by Maillard reaction in powdered state, respectively. MRPs possessed a strong 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity and reducing power (P < 0.05). The hydrolysate and glucose heated with the ratio of 2:1 at 60 °C showed high browning intensity and good antioxidant properties (P < 0.05). According to the correlation coefficients of variables included in the hydrolysate–glucose system, good correlations were observed among the antioxidant activities, the absorbance at 294 nm and the loss of free amino groups. The results suggested that Maillard reaction has a good potential to improve the antioxidant activity of SPH.

CHANGES IN SALT EXTRACTABLE PROTEIN AND CA2+‐ATPASE ACTIVITY OF MINCE FROM SILVER CARP (HYPOPHTHALMICHTHYS MOLLITRIX) DURING FROZEN STORAGE: A KINETIC STUDY

ABSTRACT Changes in salt extractable protein (SEP) and Ca2 + ‐ATPase activity of actomyosin from washed and unwashed silver carp stored at −10 and −20C were investigated. The resultant decrease of SEP and Ca2 + ‐ATPase activity mainly occurred in the first 5 and 7 weeks, and the changes obeyed first‐order model. The kinetic models of SEP and Ca2 + ‐ATPase changes were established during frozen storage. The rate constant k of decline in SEP and Ca2+‐ATPase activity of samples stored at −10C were higher than that of samples stored at −20C; the D value of samples stored at −10C were lower than that of samples stored at −20C. Compared with washed samples, unwashed samples had a higher rate constant k and activation energies E, and a lower D value. Activation energies E of SEP were higher than E of Ca2+‐ATPase activity in all samples.PRACTICAL APPLICATIONSSilver carp is one of the main freshwater fish species in China. Washing is an important step for fish processing and temperature is an important factor on fish protein storage. The changes of the kinetic models of SEP and Ca2+‐ATPase during frozen storage can explain the effect of temperature and time on silver carp mince quality. These kinetic models can be used to predict the silver carp protein functional changes during frozen storage, and help to provide better methods to effectively utilize silver carp protein resource.

Antioxidant and biochemical properties of protein hydrolysates prepared from Silver carp ( Hypophthalmichthys molitrix)

The antioxidant and biochemical properties of enzymatically hydrolyzed silver carp ( Hypophthalmichthys molitrix) protein were studied. The molecular weight of the main peaks of the hydrolysates by both Alcalase and Flavourzyme was lower than 5000 Da. The hydrolysates treated by Alcalase for ⩾1.5 h (hydrolysis time) showed that the relative proportion of <1000 Da fraction was more than 60%. For the biochemical properties, hydrolysis by both enzymes increased protein solubility to above 75% over a wide pH range; and when the hydrolysis time was prolonged (>3 h), the colour of the hydrolysates turned yellowish. The protein hydrolysates exhibited significant hydroxyl radical-scavenging activity and inhibited linoleic acid peroxidation. For Alcalase treatment, the hydroxyl radical-scavenging activity and the inhibition of linoleic acid peroxidation of hydrolysates appeared to reach a maximum level for 1.5, 2.0 h of hydrolysis, respectively; and their antioxidant activity was close to that of α-tocopherol in a linoleic acid emulsion system, and carnosine in the 2-deoxyribose oxidation system. The hydrolysate with lower molecular weight distribution possessed stronger Fe 2+ chelation ability at a sample concentration of 5.0 mg/mL. The results suggested that the antioxidant activity of silver carp protein hydrolysates were related to its degree of hydrolysis (DH), hydrolysis time and molecular weight.