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BACKGROUND: Sturgeon cartilage type II collagen peptides (SHCPs) can self‐assemble and be used to prepare collagen peptide assemblies. Self‐assembled peptides have great potential for applications in the food industry. In the present study, self‐assembled peptides were prepared from sturgeon cartilage and then characterized. RESULTS: The SHCPs self‐assembled and formed collagen peptide assemblies. After response surface experiment optimization, the optimal enzyme digestion process comprised 43.1 °C, 3.37 h and 0.96% enzyme addition, and the peptide yield was 78.46%. Physicochemical analysis showed that the SHCPs were amphiphilic, with an average molecular weight of 1081 Da, and were rich in hydrophobic amino acids. Peptide sequence identification showed that the peptides of SHCPs with polar amino acids followed by hydrophobic amino acids could be self‐assembled through hydrogen bonding and hydrophobic interaction. Through turbidity experiments, Fourier transform infrared spectroscopy and scanning electron microscopy, we demonstrated that SHCPs can self‐assemble into reticular and tubular structures under specific conditions. Furthermore, both the SHCPs‐Ca and SHCPs‐Mg assemblies were stabilized within a pH range consistent with that of the human gastrointestinal tract. CONCLUSION: The present study provides a simple and safe method for preparing novel self‐assembled peptide materials from sturgeon by‐products, providing a scientific basis for the exploitation of sturgeon cartilage and potentially reducing resource wastage. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: This study aimed to evaluate the effect of chitosan (CHI) combined electrolytic water (EW) cold sterilisation on muscle quality and myofibril proteins (MP) of large yellow croaker (Pseudosciaena crocea) during 12 days of refrigerated storage (4 °C). After the storage period, the sample of the EW + CHI group had the highest rate of hardness (36.68%), springiness (16.11%) among the control group without any treatment (CON), CHI group and EW group and similar tendencies were found in chewiness and cohesiveness. The MP content in the CON group decreased sharply from 80.35 mg g−1 to 57.90 mg g−1, in contrast to the EW + CHI group, which decreased from 81.65 mg g−1 initially to 80.83 mg g−1. The conformation of MP α‐helix and β‐sheet was retained to protect the secondary structure, and the exposure of aromatic amino acid residues was constrained to defend the tertiary structure in EW + CHI treatment which effectively delayed the degradation of MP. Based on these outcomes, EW + CHI treatment could significantly maintain the MP of large yellow croakers and prevent corruption during refrigerated storage. [ABSTRACT FROM AUTHOR]

Background: Large yellow croaker is highly perishable during storage because of high protein and moisture content. The degradation of the fish is mainly attributed to microbial growth and enzyme activity, so it is important to find an efficient storage method to extend its shelf life. Methodology: This study investigated the effect of a low‐voltage electrostatic field combined with partial freezing treatment on the physicochemical properties of myofibrillar protein (MP) and metabolomic analysis of large yellow croaker during preservation. The samples in chilled storage (C), partial freezing storage (PF) and 6 kV/m low‐voltage electrostatic field partial freezing storage (LVEF‐PF) were analyzed during an 18 day storage period. Results: In comparison with the C and PF groups, LVEF‐PF delayed the oxidation of MP by inhibiting the formation of carbonyl groups (2.25 nmol/mg pro), and maintaining higher sulfhydryl content (29.73 nmol/mg pro). Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy analysis also demonstrated that the LVEF‐PF treatment maintained the stability of the protein structure by increasing the a‐helix ratio (19.88%) and reducing the random coil ratio (17.83%). Scanning electron microscopy showed that, compared with the LVEF‐PF group, there was more degeneration and aggregation of MP in the C and PF groups after 18 days' storage. The results of untargeted metabolomic analysis showed that 415 kinds of differential metabolites were identified after storage, and the difference levels of differential metabolites were least between the samples treated with LVEF‐PF stored on the ninth day and the fresh samples. The main differential metabolic pathways during storage were amino acid metabolism and lipid metabolism. Conclusion: The LVEF‐PF treatment could maintain the stability of myofibrillar protein in large yellow croaker during storage. These results showed a potential application of the LVEF‐PF method for aquatic product preservation. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

BACKGROUND: Porcine nasal cartilage type II collagen‐derived peptides (PNCPs) may be complexed with calcium to provide a highly bioavailable, low‐cost, and effective calcium food supplement. However, the calcium‐binding characteristics of PNCPs have not yet been investigated. In the present study, calcium‐binding peptides were derived from porcine nasal cartilage type II collagen and the resulting PNCPs‐Ca complex was characterized. RESULTS: The study reveals that the calcium‐binding capacity of PNCPs is closely related to enzymatic hydrolysis conditions. The highest calcium‐binding capacity of PNCPs was observed at a hydrolysis time of 4 h, temperature of 40 °C, enzyme dosage of 1%, and solid‐to‐liquid ratio of 1:10. Scanning electron microscopy and energy dispersive X‐ray spectroscopy revealed that the PNCPs had a pronounced capacity for calcium binding, with the PNCPs‐Ca complex exhibiting a clustered structure consisting of aggregated spherical particles. Fourier‐transform infrared spectroscopy, fluorescence spectroscopy, X‐ray diffraction, dynamic light scattering, amino acid composition, and molecular weight distribution analyses all indicated that the PNCPs and calcium complexed via the carboxyl oxygen and amino nitrogen atoms, leading to the formation of a β‐sheet structure during the chelation process. In addition, the stability of the PNCPs‐Ca complex was maintained over a range of pH values consistent with those found in the human gastrointestinal tract, facilitating calcium absorption. CONCLUSION: These research findings suggest the feasibility of converting by‐products from livestock processing into calcium‐binding peptides, providing a scientific basis for the development of novel calcium supplements and the potential reduction of resource waste. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Oxygen reduction reaction (ORR) is vital for clean and renewable energy technologies, which require no fossil fuel but catalysts. Platinum (Pt) is the best‐known catalyst for ORR. However, its high cost and scarcity have severely hindered renewable energy devices (e.g., fuel cells) for large‐scale applications. Recent breakthroughs in carbon‐based metal‐free electrochemical catalysts (C‐MFECs) show great potential for earth‐abundant carbon materials as low‐cost metal‐free electrocatalysts towards ORR in acidic media. This article provides a focused, but critical review on C‐MFECs for ORR in acidic media with an emphasis on advances in the structure design and synthesis, fundamental understanding of the structure‐property relationship and electrocatalytic mechanisms, and their applications in proton exchange membrane fuel cells. Current challenges and future perspectives in this emerging field are also discussed. [ABSTRACT FROM AUTHOR]

BACKGROUND Sea cucumber ( Stichopus japonicus) ovum hydrolysates (SCOHs) chelated with calcium were produced to investigate the characteristics of calcium binding and solubility, as well as to study any effects on calcium absorption by human intestinal epithelial cells. RESULTS The results of the present study show that the calcium-binding capacity of SCOHs depended greatly on the type of proteases. The maximum level of Ca binding (0.38 mmol L-1) occurred when trypsin was used, with a peptide yield of 85.7%. Investigation of the possible chelating modes between SCOHs and calcium ions indicated that calcium ions bound to SCOHs primarily via interactions with carboxyl oxygen and amino nitrogen atoms of Glu and Asp and also that the phosphoserine residues might be also responsible for SCOH-calcium chelation. Moreover, SCOH-calcium complexes maintained the solubility of calcium under simulated gastrointestinal digestion, regardless of the presence of dietary components such as oxalate. Furthermore, SCOH-Ca led to higher peak intracellular [Ca2+]i in both Caco-2 cells (338.3 nmol L-1 versus 269.6 nmol L-1) and HT-29 cells (373.9 nmol L-1 versus 271.7 nmol L-1) than casein phosphopeptide-Ca. CONCLUSION Carboxyl oxygen and amino nitrogen atoms in the SCOHs could bind calcium ions, forming SCOH-calcium complexes. These complexes improved calcium solubility under simulated gastrointestinal digestion and also promoted calcium absorption in Caco-2 and HT-29 cells. © 2017 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This study aimed to determine optimum preparation conditions of sea cucumber ovum hydrolysates-calcium ( SCOHs-Ca) complexes by Box-Behnken design and further elucidate their microstructure characteristics using Fourier transform infrared spectroscopy, scanning electron microscope, atomic force microscopy and dynamic light scattering. The predicted calcium-chelating capacity under the optimum conditions of the process variables was very close to the experimental value (53.45 ± 0.29 mg g−1) determined in the batch experiment. Results demonstrated that the calcium bind to the SCOHs to form the SCOHs-Ca complexes primarily via interactions with carboxyl oxygen and amino nitrogen atoms. The prepared SCOHs-Ca complexes formed compact nanoparticles and exhibited a fold and porous network structure. These changes could be attributed to the interaction between peptides and calcium ions. Our findings provide a theoretical basis for the development of new calcium preparations as well as the high-value utilisation of sea cucumber by-products. [ABSTRACT FROM AUTHOR]