Preparation process optimization of pig bone collagen peptide-calcium chelate using response surface methodology and its structural characterization and stability analysis

Purification, characterization, and functional validation of a novel casein complex enzyme hydrolysate-binding calcium

Food Peptide Calcium Chelate was an excellent calcium supplement. The aim of this study was to isolate peptides with high calcium binding activity from a mixture of casein hydrolyzed peptides, to determine their structural characteristics and to verify their function. Firstly, micellar casein was hydrolyzed by a combination of flavor protease and trypsin. Casein hydrolysate peptides (CHP) with high calcium chelating activity were obtained by three purifications and characterized by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS), mass spectrometry (MS/MS), and fourier transform infrared spectroscopy (FTIR). The results showed that the purified polypeptide (Tyr-Gln-Glu-Pro) had high calcium binding capacity (70.10 ± 4.23 μg/mg). Animal experiments confirmed that YQEP-Ca was effective in improving the bone microarchitecture of rats, and that the low-calcium-content's medium-dose group also had better utilization than the inorganic and unchelated calcium groups. Therefore, the YQEP-Ca obtained in this study provides new clues for the development of various products.

Structural characterization and stability studies of hemp peptides and chelates for efficient chelation of ferrous ions

Synthesis of peptide-iron chelates provides a novel approach to alleviating iron deficiency in humans. The study used hemp protein isolate to make hemp protein hydrolysates (HPHs), which were combined with ferrous chloride to make hemp protein peptide iron chelates (HPH-Fe). The HPH-Fe were structurally characterized and analyzed for stability. The strongest ferrous ion-binding fraction HPH-I (<3 kDa) was isolated by ultrafiltration, and Sephadex G-15 was used to obtain fractions with high ferrous ion-binding capacity (82.47%), identified by amino acid sequences as QASSDGFEWVSFK (1482.31 Da), ARVDWKETPE (1223.53 Da), ILLPSF (719.34 Da), and WLNGGP (643.32 Da). Aspartic acid, lysine, glutamic acid, glycine, and histidine in HPH-Fe were involved in the chelation reaction. HPH-Fe maintained a good chelation rate at 25-65°C, pH = 4.0-7.0, stability during 35 days of storage at ambient temperature, and in vitro digestion tolerance. This study presents HPH-Fe as a potential alternative to chemical iron supplements in food. PRACTICAL APPLICATION: Preparation of novel, highly efficient ferrous iron ion hemp peptide and its chelates by hydrolysis, separation, and enrichment using hemp protein as raw material. Aspartic acid, glutamic acid, glycine, lysine, and histidine in HPH-Fe were involved in the chelating reaction. The peptides QASSDGFEWVSFK, ARVDWKETPE, ILLPSF, and WLNGGP showed high ferrous ion binding capacity. Iron chelates of hemp protein peptides have good acid resistance, storage stability, and digestive properties.

Improvement of stability and antioxidant capacity of peptide - iron complexes by sonication

In the present study, peptide‑iron complexes derived from Dictyophora rubrovolvata volva (U-VP-Fe) were prepared using ultrasonication. Their structures, interactions, stability and antioxidant activity were systematically characterised. The production conditions optimized by orthogonal tests were as follows: ultrasonic power 90 W, peptide concentration 4 %, mass ratio of peptide/FeCl2 1:1, and pH 4. Under such conditions, the iron binding capacity could reach 66.35 mg/g. Fluorescence spectral analyses revealed that hydrophobic forces dominated the binding to Fe2+, and the binding process was endothermic and spontaneous. Morphological analyses showed that U-VP-Fe featured a dense and smooth surface with significantly improved surface hydrophobicity and particle size. Stability analyses suggested that U-VP-Fe exhibited better resistance to high temperature, pH and gastrointestinal digestion than the hydrothermal control (C-VP-Fe). Antioxidant assays demonstrated that U-VP-Fe presented superior antioxidant capacity than C-VP-Fe. The findings lay the theoretical foundation for applying ultrasound method to produce peptide‑iron complexes as novel iron supplements.

Development and characterization of gelatin peptides and peptide‑calcium chelates from tuna processing by-products of skins and bones

This study used hydrothermal extraction to obtain gelatin from tuna processing by-products. After treatment, the yield (w/w dry weight) of gelatin from skins and bones were 70.22 ± 2.07 % and 28 ± 3.03 %, respectively. Enzymatic hydrolysis using alkaline protease and pancreatin converted the gelatins into peptides, with the content of oligopeptide up to 87.67 ± 1.44 %. The tuna bone gelatin peptides exhibiting higher scavenging abilities against hydroxyl radicals (·OH-), 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH·), and hydrogen peroxide (H2O2) compared to tuna skin gelatin peptides. Gelatin peptides were chelated with CaCl2 at 50 °C for 60 min, pH 8.0, and a 1:2 peptide-to‑calcium ratio, achieving a maximum calcium binding capacity of 56.70 ± 1.67 %. Fourier-transform infrared spectroscopy indicated the participation of amino and carboxyl groups in the reaction. These findings provide technical and theoretical support for the development of calcium-chelated gelatin peptides.

Characteristics and food applications of aquatic collagen and its derivatives: A review

Collagen and its hydrolysates have high bioavailability, good biocompatibility, biodegradability, and biological activity which has meant that they have been widely used in food, medicine, cosmetics, and other industries. Although the properties and applications of collagen have been reviewed recently, few studies have focused on aquatic collagen. To provide readers with a deeper understanding of aquatic collagen, this review addresses the structure and properties of aquatic collagen and compares them with mammalian collagen, as well as the differences between collagen, gelatin, and collagen peptides. In contrast to mammalian collagen, aquatic collagen prevents zoonotic diseases, reduces environmental pollution, improves the utilization of aquatic resources, and facilitates the extraction and separation of active oligopeptides. Additionally, methods for screening functional peptides using in vitro digestion have been introduced. Finally, the review focuses on the applications of collagen and its derivatives in food preservation (packaging films, coatings, additives, and antifreeze peptides), drug delivery (microcapsules, emulsions, nanoparticles, and hydrogels), nutrition, and healthcare.

Preparation, structural characterisation, absorption and calcium transport studies of walnut peptide calcium chelate

In this study, a walnut peptide (WP) with calcium-binding capacity was prepared using a combination of alkalase and neutrase. The conditions for the preparation of walnut peptide calcium chelate (WP-Ca) were optimised (a peptide/calcium chloride ratio of 1 : 4 for 70 min at 50 °C and pH 9.5). Fractionation via ultrafiltration showed that peptides with a size <1 kDa demonstrated the highest calcium binding capacity at 106.4 mg g-1. Scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, zeta potential and other analyses were performed to characterize WP-Ca. The combined results indicate that calcium binds by interacting with the carboxyl oxygen, hydroxyl oxygen and amino nitrogen of walnut peptides to form WP-Ca. The chelate showed good gastrointestinal stability. Furthermore, using the Caco-2 cell monolayer model, WP-Ca was shown to significantly increase calcium bioavailability and effectively reverse the inhibitory effects of dietary factors (phytates and phosphates) on calcium absorption. The results provide a scientific basis for developing novel calcium supplements and high-value walnut utilisation.

Glycated walnut meal peptide‑calcium chelates (COS-MMGGED-Ca): Preparation, characterization, and calcium absorption-promoting

This study isolated a novel peptide MMGGED with strong calcium-binding capacity from defatted walnut meal and synthesized a novel peptide‑calcium chelate COS-MMGGED-Ca with high stability via glycation. Structural characterization and computer simulation identified binding sites, while in vitro digestion stability and calcium transport experiments explored the chelate's properties. Results showed that after glycation, COS-MMGGED bound Ca2+ with 88.75 ± 1.75 %, mainly via aspartic and glutamic acids. COS-MMGGED-Ca released Ca2+ steadily (60.27 %), with thermal denaturation temperature increased by 18 °C and 37 °C compared to MMGGED-Ca, indicating good processing performance. Furthermore, COS-MMGGED significantly enhanced Ca2+ transport across Caco-2 monolayers, 1.13-fold and 1.62-fold higher than CaCl2 and MMGGED, respectively, at 240 h. These findings prove glycation enhances structural properties, stability, calcium loading, and transport of peptide‑calcium chelates, providing a scientific basis for developing novel efficient calcium supplements and high-value utilization of walnut meal.

Novel Insights Into Peptide-Calcium Chelates From Lentinula edodes: Preparation and Its Structure, Stability, and Calcium Transport Analysis

Peptide-Ca chelates are innovative calcium supplements. Lentinula edodes possesses nutritional advantages for preparing calcium-binding peptides (CBPs), although there are limited studies on this subject. Therefore, this paper investigated the optimal condition for preparing Lentinula edodes CBPs and Lentinula edodes peptide-calcium chelates (LP-Ca), along with analyzing their microstructure, calcium-binding mechanisms, stability, and calcium transporting efficacy. The optimal protease and hydrolysis time for preparing CBPs were neutral protease and 3 h, respectively. The optimized parameters for LP-Ca preparation were as follows: pH9, time 50 min, mass ratio of peptide/CaCl2 5:1, and temperature 65°C. The chelates contain 4.23% ± 0.01% Ca. After chelation, Glu, Asp, Lys, Ser, His, and Cys were enriched. LP-Ca possessed a rough and porous structure, exhibiting a pronounced calcium signal. -COO-, C=O, and N-H groups were contributed to the chelation, with calcium primarily existing in an amorphous form. LP-Ca exhibited enhanced thermal stability and retained most of the calcium (62.33% ± 4.51%) after digestion, and calcium transportation was enhanced in the LP-Ca group (9.57 ± 0.60 μg). Collectively, LP-Ca are studied for the first time and the study is of great significance for developing novel calcium supplements.

Preparation, characterization, stability and replenishing calcium ability of Moringa oleifera leaf peptide-calcium chelates

Calcium deficiency has garnered significant attention as a global public health issue. A new generation of calcium supplements, peptide-calcium chelates, is expected to increase in market value. In this study, we produced MORP (MW < 1 kDa) from Moringa oleifera leaf protein via enzymatic hydrolysis for chelation with Ca2+ to produce MORP-Ca. SEM, EDS, FTIR and FS characterized the structure of MORP-Ca. The results indicate alterations in both the appearance and internal structure of MORP following calcium chelation. The functional groups of N-H, C-H, C-N, -C = O, -COO-, C-O, and -OH in MORP are involved in chelating Ca2+ to form MORP-Ca. In addition, MORP-Ca exhibits poor stability in the stomach; however, it demonstrates high stability in the intestine and under various temperature conditions. The results of the cellular experiments demonstrated that MORP-Ca is an effective promoter of calcium transport and absorption. MORP-Ca effectively increased bone mineral density and improved bone formation in animal studies. In addition, MORP-Ca supplementation improved the gut microbiota imbalance in rats fed a calcium-deficient diet, resulting in an increase in Firmicutes and a decrease in Actinobacteria. Thus, there is a connection between altered gastrointestinal flora and calcium absorption. LC-MS/MS and molecular docking analyses identified ARNEGRDL, RELIIGDR, YTPDYETK, YYTPDYETK, and IKFEFPAVDTL as key peptide sequences for the calcium-supplementing role of MORP (MW < 1 kDa). These results establish a theoretical foundation for the use of MORP-Ca as a calcium supplement or functional food.

Preparation and Characterization of Calcium-Chelated Sea Cucumber Ovum Hydrolysate and the Inhibitory Effect on α-Amylase

α-amylase can effectively inhibit the activity of digestive enzymes and alter nutrient absorption. The impact of ovum hydrolysates of sea cucumbers on α-amylase activity was investigated in this study. The protein hydrolysates generated using different proteases (pepsin, trypsin, and neutral protease) and molecular weights (less than 3000 and more than 3000) were investigated. The results showed that all three different hydrolysates demonstrated calcium-chelating activity and induced a fluorescence-quenching effect on α-amylase. The sea cucumber ovum hydrolysate with a molecular weight of less than 3000 Da, isolated using trypsin, showed the most effective inhibitory effect on α-amylase, with an inhibition rate of 53.9%, and the inhibition type was identified as mixed forms of inhibition. In conclusion, the generation and utilization of protein hydrolysates from sea cucumber ovum as a functional food ingredient could be a potential approach to add value to low-cost seafood by-products.

Antioxidant peptides from silver carp steak by alkaline protease and flavor enzyme hydrolysis: Characterization of their structure and cytoprotective effects against H2O2-induced oxidative stress

Silver carp steak is a rarely utilized silver carp processing byproduct. This study aimed to optimize a dual enzymatic method to extract antioxidant peptide components from silver carp steak and characterize their structure and in vitro antioxidant activity through ultrafiltration purification, response surface methodology, molecular docking, and radical scavenging activity analysis. The optimal extraction conditions for silver carp steak antioxidant peptides (SCSAP) were determined as 1:6 solid-liquid ratio, 1500 U/g alkaline protease addition, 4 h alkaline protease hydrolysis time, 1946 U/g flavor enzyme addition, and 2.5 h flavor enzyme hydrolysis time. The <3 kDa SCSAP component (SCSAP-3kDa) showed the strongest antioxidant activity, with its 1,1-diphenyl-2-trinitrophenyl hydrazine (DPPH) radical scavenging rate, ABTS radical scavenging rate, hydroxyl radical scavenging rate, metal ion chelating rate, and reducing capacity reaching 88.75%, 91.21%, 67.02%, 69.07%, and 0.985, respectively. Moreover, the three peptides (PF-7, GP-8, and YF-10) of 100 µg/mL could protect HepG2 cells from oxidative stress damage by reducing the oxidative damage level and activating Keap1-Nrf2-ARE pathways, enabling an increase of superoxide dismutases (SOD) activity, and a decrease of malondialdehyde (MDA) content and reactive oxygen species (ROS) level. The integrated results indicate the enormous potential of SCSAP-3kDa as a functional food ingredient in the food industry. PRACTICAL APPLICATION: This study selected the antioxidant capacity of silver carp steak peptides as the index and developed a facile dual enzymatic hydrolysis method to obtain three antioxidant peptides (PF-7, GP-8, and YF-10) with biological activity, providing a theoretical basis for bioavailability of antioxidant peptides from silver carp steak and contributing to their application in new functional foods.

Designing calcium-fortified milk for improving stability and calcium bioaccessibility by solid dispersion emulsification

Approximately 70 % of the calcium intake in the adult diet worldwide is derived from dairy products. However, insoluble calcium salts, which are usually added directly during dairy production, have poor suspension stability and are prone to precipitation. The current study aimed to address the constraints of conventional production methods by utilizing solid dispersion emulsification technology to inhibit the aggregation of calcium salts. Calcium-fortified milk samples with different calcium content were prepared and compared with the commercial calcium-fortified milk, and their physicochemical, microstructural, and digestive properties were characterized. The results of this study demonstrated that all the prepared calcium-fortified milk samples exhibited a particle size of approximately 270 nm and a zeta-potential of approximately -40 mV. The calcium-fortified milk, which has been produced using solid dispersed emulsion technology, has been found to have 1.8 times more physical stability than commercial milk. Microstructural studies showed that aggregation of milk with more than 225 mg/100 mL calcium content occurred. During in-vitro digestion, it was found that the increasing calcium loading did not impact protein digestion without the creation of new fragments in the calcium-fortified milk. Calcium bioaccessibility was enhanced by approximately 50 % in comparison with the commercial product. While the release of free fatty acids was found to decrease with increasing calcium content. This study facilitates the development and utilization of calcium-fortified and low-fat foods and provides a new idea for the addition of milk minerals in dairy products.

Long-term stable water-in-oil-in-water emulsion for effective protection and sustained release of lysine-calcium using chitosan and hydroxypropyl methyl cellulose

The poor tolerance to gastric acid and low absorption of calcium supplements in the intestinal tract remain a serious limitation in applications. Herein, lysine-calcium (Lys-Ca) has been synthesized via the chelation of Lys and high-temperature calcination scallop shell powder (HCSP), and subsequently encapsulated in a carefully designed water-in-oil-in-water (W/O/W) emulsion with a high encapsulation efficiency of 93 % using chitosan (CS) and hydroxypropyl methylcellulose (HPMC). Owing to the interfacial film formed by CS and HPMC between the droplets, the resulting emulsion demonstrates good acid and thermal stability, as well as long-term stability even after 60 d of storage at 25 °C. Meanwhile, the emulsion effectively protects the encapsulated Lys-Ca from damage in simulated gastric fluid (SGF). with only about 20 % Lys-Ca escaping into SGF (after 4 h). In simulated intestinal fluid (SIF), it sustainedly releases with a 61 % ratio at 1 h under the influence of bile salts and lipase, and near-complete release occurred after 6 h. Additionally, the emulsion presents no cytotoxicity and possesses appreciable calcium transport capacity. This work provides a well-designed double-emulsion strategy that offers a promising approach for developing efficient calcium supplements, aiming at improving the bioavailability of biomass calcium.

Structural, antioxidant activity, and stability studies of jellyfish collagen peptide-calcium chelates

The aim of this study was to prepare and characterize jellyfish collagen peptide (JCP)-calcium chelates (JCP-Ca) using peptides with different molecular weights. Further analysis revealed that the low-molecular-weight jellyfish collagen peptide (JCP1) had a higher chelation rate. Structural characterization showed that functional groups such as N-H, C[bond, double bond]O, and -COO were involved in the formation of JCP-Ca, which shifted towards a more ordered and regular structure, and smaller-molecular-weight peptides were more likely to form a denser structure. In addition, JCPs chelated with calcium ions showed excellent antioxidant capacity. JCP-Ca showed good stability in heat-treated and gastrointestinal environments, whereas the antioxidant activity was significantly reduced under highly acidic conditions. The present study addresses the knowledge gap regarding the physicochemical properties of JCP-Ca and establishes a solid research foundation for its associated products.

Spatial distribution of antioxidant activity in baguette and its modulation of proinflammatory cytokines in RAW264.7 macrophages

Baguette is a globally acclaimed bakery staple, composed by a crispy crust and soft crumb, both containing Maillard reaction products (MRPs) with potential bioactivities. However, MRPs' impacts on the nutritional and health attributes of baguette, particularly in terms of cellular and biological functions, are yet to be clearly elucidated. This study chemically characterizes the crust and crumb of baguettes and investigates the influence of the Maillard reaction on baguette's nutritional profile, especially in the antioxidant and anti-inflammatory effects. The findings indicate an increase in browning intensity and advanced glycation end products (AGEs) from the baguette's interior to its exterior, alongside a significant rise in the antioxidant capacity of the crust, suggesting the Maillard reaction's role in boosting antioxidative properties. Both the crust and crumb demonstrated strong cytocompatibility with immune cells, capable of reducing cellular oxidative stress and regulating intracellular free radical levels. The crust effectively countered peroxyl radical-induced cell membrane hyperpolarization by 91% and completely neutralized the suppression of oxygen respiration in mitochondria, displaying higher efficacy than the crumb. In contrast, crumb extracts were more potent in inhibiting lipopolysaccharide-induced expression of proinflammatory cytokines, such as interleukins-1β (IL-1β) and IL-6, in macrophages. It could provide the fundamental data and cell-based approach for investigating the biological impacts of bread on immune responses, contributing to the refinement and supplementation of nutritional recommendations.

Deer Skin Collagen Peptides Bound to Calcium: In Vitro Gastrointestinal Simulation of Digestion, Cellular Uptake and Analysis of Antioxidant Activity

The by-product of deer skin, which has mostly been used as a decorative material, is rich in collagen and amino acids that could bind to Ca2+. Therefore, the preparation process, stability, antioxidant activity and calcium transport capacity of deer skin collagen peptide calcium chelate (Ca-DSCP) were investigated. In addition, the structure of the new chelate was characterized. The preparation process of Ca-DSCP was optimized using one-way experiments and response surface methodology. The ideal conditions were pH 9, 48 °C, and a peptide-to-calcium mass ratio of 5:1. The chelation rate was (60.73 ± 1.54)%. Zeta potential, XRD, UV-vis and FTIR analyses yielded that deer skin collagen peptides (DSCP) underwent a chelating reaction with calcium ions to form new structures. The stability of Ca-DSCP and the fraction of bioavailability of calcium ions were determined using in vitro gastrointestinal digestion and a Caco-2 cell monolayer model. The results showed that fraction of bioavailability and stability of DSCP were improved by influencing the structural characterization. The antioxidant activities of DSCP and Ca-DSCP were evaluated by measuring relevant oxidative stress indicators, DPPH radical scavenging capacity and hydroxyl radical scavenging capacity. Finally, bioinformatics and molecular docking techniques were utilized to screen and study the antioxidant mechanism of DSCP.

Digestion and absorption characteristics of iron-chelating silver carp scale collagen peptide and insights into their chelation mechanism

Iron deficiency is widespread throughout the world, supplementing sufficient iron or improving the bioavailability of iron is the fundamental strategy to solve the problem of iron scarcity. Herein, we explored a new form of iron supplement, iron chelates of silver carp scales (SCSCP-Fe) were prepared from collagen peptide of silver carp scales (SCSCP) and FeCl2·4H2O, the effects of external environment and simulated gastrointestinal digestive environment on the stability of SCSCP-Fe and the structural changes of peptide iron chelates during digestion were investigated. The results of in vitro iron absorption promotion showed that the iron bioavailability of SCSCP-Fe was higher than that of FeSO4. Two potential high iron chelating peptides DTSGGYDEY (DY) and LQGSNEIEIR (LR) were screened and synthesized from the SCSCP sequence by molecular dynamics and LC-MS/MS techniques. The FTIR results displayed that the binding sites of DY and LR for Fe2+ were the carboxyl group, the amino group, and the nitrogen atom on the amide group on the peptide. ITC results indicated that the chelation reactions of DY and LR with Fe2+ were mainly dominated by electrostatic interactions, forming chelates in stoichiometric ratios of 1:2 and 1:1, respectively. Both DY and LR had a certain ability to promote iron absorption. The transport of DY-Fe chelate may be a combination of the three pathways: PepT1 vector pathway, cell bypass, and endocytosis, while LR-Fe chelate was dominated by bivalent metal ion transporters. This study is expected to provide theoretical reference and technical support for the high-value utilization of silver carp scales and the development of novel iron supplements.

Preparation, Characterization and Stability of Calcium-Binding Peptides Derived from Chicken Blood

Calcium-binding peptides have gained significant attention due to their potential applications in various fields. In this study, we aimed to prepare, characterize, and evaluate the stability of calcium-binding peptides derived from chicken blood. Chicken hemoglobin peptides (CPs) were obtained by protease hydrolysis and were applied to prepare chicken hemoglobin peptide-calcium chelate (CP-Ca). The preparation conditions were optimized, and the characteristics and stability of CP-Ca were analyzed. The optimal chelating conditions were determined by single-factor and response surface tests, and the maximum calcium ion chelating rate was 77.54%. Amino acid analysis indicated that glutamic acid and aspartic acid motifs played an important role in the chelation of the calcium ions and CP. According to the characterization analysis, CP-Ca was a different substance compared with CP; calcium ions chelated CPs via the sites of carbonyl oxygen, carboxyl oxygen, and amino nitrogen groups; and after the chelation, the structure changed from a smooth homogeneous plate to compact granular. The stability analysis showed that CP-Ca was stable at different temperatures, pH, and gastrointestinal conditions. The study indicates that chicken blood is a promising source of peptide-calcium chelates, providing a theoretical basis for application in functional foods and improving the utilization value of chicken blood.

Enhancement of Calcium Chelating Activity in Peptides from Sea Cucumber Ovum through Phosphorylation Modification

Recently, phosphorylation has been applied to peptides to enhance their physiological activity, taking advantage of its modification benefits and the extensive study of functional peptides. In this study, water-soluble peptides (WSPs) of sea cucumber ovum were phosphorylated in order to improve the latter's calcium binding capacity and calcium absorption. Enzymatic hydrolysis methods were screened via ultraviolet-visible absorption spectroscopy (UV-Vis), the fluorescence spectrum, and calcium chelating ability. Phosphorylated water-soluble peptides (P-WSPs) were characterized via high-performance liquid chromatography, the circular dichroism spectrum, Fourier transform infrared spectroscopy (FTIR), UV-Vis spectroscopy, surface hydrophobicity, and fluorescence spectroscopy. The phosphorus content, calcium chelation rate and absorption rate were investigated. The results demonstrated that phosphorylation enhanced the calcium chelating capacity of WSPs, with the highest capacity reaching 0.96 mmol/L. Phosphate ions caused esterification events, and the carboxyl, amino, and phosphate groups of WSPs and P-WSPs interacted with calcium ions to form these bonds. Calcium-chelated phosphorylated water-soluble peptides (P-WSPs-Ca) demonstrated outstanding stability (calcium retention rates > 80%) in gastrointestinal processes. Our study indicates that these chelates have significant potential to develop into calcium supplements with superior efficacy, bioactivity, and stability.

Mineral-element-chelating activity of food-derived peptides: influencing factors and enhancement strategies

Mineral elements including calcium, iron, and zinc play crucial roles in human health. Their deficiency causes public health risk globally. Commercial mineral supplements have limitations; therefore, alternatives with better solubility, bioavailability, and safety are needed. Chelates of food-derived peptides and mineral elements exhibit advantages in terms of stability, absorption rate, and safety. However, low binding efficiency limits their application. Extensive studies have focused on understanding and enhancing the chelating activity of food-derived peptides with mineral elements. This includes obtaining peptides with high chelating activity, elucidating interaction mechanisms, optimizing chelation conditions, and developing techniques to enhance the chelating activity. This review provides a comprehensive theoretical basis for the development and utilization of food-derived peptide-mineral element chelates in the food industry. Efforts to address the challenge of low binding rates between peptides and mineral elements have yielded promising results. Optimization of peptide sources, enzymatic hydrolysis processes, and purification schemes have helped in obtaining peptides with high chelating activity. The understanding of interaction mechanisms has been enhanced through advanced separation techniques and molecular simulation calculations. Optimizing chelation process conditions, including pH and temperature, can help in achieving high binding rates. Methods including phosphorylation modification and ultrasonic treatment can enhance the chelating activity.

Positive effect of peptide-calcium chelates from Grifola frondosa on a mouse model of senile osteoporosis

Calcium supplementation has been shown to be efficacious in mitigating the progression of senile osteoporosis (SOP) and reducing the incidence of osteoporotic fractures resulting from prolonged calcium shortage. In this study, Grifola frondosa (GF) peptides-calcium chelate were synthesized through the interaction between peptide from GF and CaCl2. The chelation reaction was shown to involve the participation of the amino and carboxyl groups in the peptide, as revealed by scanning electron microscope, Fourier-transform infrared, and ultraviolet spectrophotometry. Furthermore, a mouse model of (SOP) induced by d-galactose was established (SCXK-2018-0004). Results demonstrated that low dosage of low-molecular weight GF peptides-calcium chelates (LLgps-Ca) could significantly improve serum index and pathological features of bone tissue and reduce bone injury. Further research suggested that LLgps-Ca could ameliorate SOP by modulating the disrupted metabolic pathway, which includes focal adhesion, extracellular matrix receptor interaction, and PI3K-Akt signaling pathway. Using Western blot, the differentially expressed proteins were further confirmed. Thus, calciumchelating peptides from GF could serve as functional calcium agents to alleviate SOP.

One-step high efficiency separation of prolyl endopeptidase from Aspergillus niger and its application

Prolyl endopeptidase from Aspergillus niger (An-PEP) is an enzyme that recognizes C-terminal peptide bonds of amino acid chains and cleaves them by hydrolysis. An aqueous two-phase system (ATPS) was used to separate An-PEP from fermentation broth. Through single factor experiments, the ATPS containing 16 % (w/w) PEG2000 and 15 % (w/w) (NH4)2SO4 at pH 6.0 obtained the recovery of 79.74 ± 0.16 % and the purification coefficient of 7.64 ± 0.08. It was then used to produce soy protein isolate peptide (SPIP) by hydrolysis of soy protein isolate (SPI), and SPIP-Ferrous chelate (SPIP-Fe) was prepared with SPIP and Fe2+. The chelation conditions were optimized by RSM, as the chelation time was 30 min, chelation temperature was 25 °C, SPIP mass to VC mass was two to one and pH was 6.0. The obtained chelation rate was 82.56 ± 2.30 %. The change in the structures and functional features of SPIP before and after chelation were investigated. The FTIR and UV-Vis results indicated that the chelation of Fe2+ and SPIP depended mainly on the formation of amide bonds. The fluorescence, SEM and amino acid composition analysis results indicated that Fe2+ could induce and stabilize the surface conformation and change the amino acid distribution on the surfaces of SPIP. The chelation of SPIP and Fe2+ resulted in the enhancement of radical scavenging activities and ACE inhibitory activities. This work provided a new perspective for the further development of peptide-Fe chelates for iron supplement.

Expression, characterization and antivascular activity of amino acid sequence repeating collagen hexadecapeptide

Type V collagen is an essential component of the extracellular matrix (ECM), and its remodeling releases specific protein fragments that can specifically inhibit endothelial cell responses such as proliferation, migration, and invasion. In this study, we have successfully constructed two engineered strains of Pichia pastoris capable of producing recombinant collagen through a new genetic engineering approach. Through high-density fermentation, the expression of 1605 protein and 1610 protein could reach 2.72 g/L and 4.36 g/L. With the increase of repetition times, the yield also increased. Bioactivity analysis showed that recombinant collagen could block the angiogenic effect of FGF-2 on endothelial cells by eliminating FGF-2-induced endothelial cell migration and invasion. Collectively, the recombinant proteins we successfully expressed have a wide range of potential for inhibiting angiogenesis in the biomaterials and biomedical fields.

Novel strategy to the characterization and enhance the glycemic control properties of walnut-derived peptides via zinc chelation

This study aimed to utilize zinc coordination to promote the hypoglycemic and antioxidant properties of walnut-derived peptides, such as walnut protein hydrolysate (WPH) and Leu-Pro-Leu-Leu-Arg (LPLLR, LP5), of which LP5 was previously identified from WPH. The optimal conditions for the chelation were a peptide-to-zinc ratio of 6:1, pH of 9, duration of 50 min, and temperature of 50 °C. The WPH-Zn and LP5-Zn complexes increased the α-glucosidase inhibition, α-amylase inhibition, and antioxidant activity more than WPH and LP5 (p < 0.05). In particular, the antioxidant activity of WPH-Zn was superior to LP5-Zn. This is attributable to the WPH containing more aromatic amino acids, carboxylate groups and the imidazole groups, which implies its capacity to potentially coordinate with Zn2+ to form the WPH-Zn complex. Moreover, particle size, zeta potential, and scanning electron microscope indicated that the chelation of Zn2+ by peptides led to intramolecular and intermolecular folding and aggregation.

Glycated Walnut Meal Peptide-Calcium Chelates: Preparation, Characterization, and Stability

Finding stable and bioavailable calcium supplements is crucial for addressing calcium deficiency. In this study, glycated peptide-calcium chelates (WMPHs-COS-Ca) were prepared from walnut meal protein hydrolysates (WMPHs) and chitosan oligosaccharides (COSs) through the Maillard reaction, and the structural properties and stability of the WMPHs-COS-Ca were characterized. The results showed that WMPHs and COSs exhibited high binding affinities, with a glycation degree of 64.82%. After glycation, Asp, Lys, and Arg decreased by 2.07%, 0.46%, and 1.06%, respectively, which indicated that these three amino acids are involved in the Maillard reaction. In addition, compared with the WMPHs, the emulsifying ability and emulsion stability of the WMPHs-COS increased by 10.16 mg2/g and 52.73 min, respectively, suggesting that WMPHs-COS have better processing characteristics. After chelation with calcium ions, the calcium chelation rate of peptides with molecular weights less than 1 kDa was the highest (64.88%), and the optimized preparation conditions were 5:1 w/w for WMPH-COS/CaCl2s, with a temperature of 50 °C, a chelation time of 50 min, and a pH of 7.0. Scanning electron microscopy showed that the "bridging role" of WMPHs-COS changed to a loose structure. UV-vis spectroscopy and Fourier transform infrared spectrometry results indicated that the amino nitrogen atoms, carboxyl oxygen atoms, and carbon oxygen atoms in WMPHs-COS chelated with calcium ions, forming WMPHs-COS-Ca. Moreover, WMPHs-COS-Ca was relatively stable at high temperatures and under acidic and alkaline environmental and digestion conditions in the gastrointestinal tract, indicating that WMPHs-COS-Ca have a greater degree of bioavailability.

Structural characterisation of deer sinew peptides as calcium carriers, their promotion of MC3T3-E1 cell proliferation and their effect on bone deposition in mice

Deer sinew as a by-product has high collagen and nutritional value. This study focuses on its hydrolysate being used as a calcium carrier to develop functional foods. The chelation mechanism was analyzed by SEM, EDS, UV-vis, FTIR, and fluorescence spectroscopy and zeta potential analysis after using peptide-sequenced deer sinew peptides for chelation with calcium ions. The results showed that the chelation of deer sinew peptides with calcium ions occurs mainly at the O and N atoms of carboxyl, amino and amide bonds. In vitro and in vivo studies revealed that deer sinew peptide-calcium chelate (DSPs-Ca) promoted the proliferation of MC3T3-E1 cells without toxic side effects and increased the alkaline phosphatase activity. The DSPs-Ca group improved the bone microstructure induced by low calcium, as well as up-regulated the expression of genes responsible for calcium uptake in the kidneys, as evidenced by serum markers, bone sections, bone parameters, and gene expression analyses in low-calcium-fed mice. From the above, it can be concluded that DSPs-Ca is expected to be a calcium supplement food for promoting bone health.

A physicochemical evaluation of ossein-hydroxyapatite within the bovine bone matrix revealed demineralization and making type I collagen available as a result of processing and solubilization by acids

Bovine bone is an animal-origin matrix rich in type I collagen (COL I) and it necessitates prior demineralization and makes COL I available. This study investigated the ossein-hydroxyapatite physicochemical properties evaluation as a result of processing and solubilization by acids and revealed the bone matrix demineralization and making COL I available. The tibia residue from bovine sources was processed, ground, and transformed into bone matrix powder. The bone matrix was solubilized in acetic acid followed by lactic acid. The bone matrix was evaluated as a result of processing and solubilization by acids: ossein and hydroxyapatite percentages by nitrogen and ash content, mineral content, particle size distribution, Fourier-transformation infrared spectroscopy, x-ray diffraction, and scanning electron microscope. For the obtained residual extracts, pH and mineral content were evaluated. The solubilization by acids affected the ossein-hydroxyapatite physicochemical properties, and the bone matrix solubilized by acetic and lactic acid showed the preservation of the ossein alongside the loss of hydroxyapatite. The processing and the solubilization by acids were revealed to be a  alternative to bone matrix demineralization and enabling the accessibility of bone COL I. PRACTICAL APPLICATION: Bovine bone is an abundant type I collagen source, but processing maneuvers and demineralization effect present limitations due to the rigidity of the structural components. Exploring methodologies to process and demineralize will allow type I collagen to be obtained from the bone source, and direct and amplify the potentialities in the chemical and food industries. The research focused on bone sources and collagen availability holds paramount significance, and promotes repurposing agribusiness residues and development of protein-base products.

Regulation of ovalbumin allergenicity and structure-activity relationship analysis based on pulsed electric field technology

The study focused on the regulation of ovalbumin (OVA) allergenicity using pulsed electric field (PEF) technology and examined the structure-activity link. Following PEF treatment, the ability of OVA to bind to IgE and IgG1 at 6 kHz was inhibited by 30.41 %. According to the microstructure, PEF caused cracks on the OVA surface. Spectral analysis revealed a blue shift in the amide I band and a decrease in α-helix and β-sheet content indicating that the structure of OVA was unfolded. The disulfide bond conformation was transformed and the structure tended to be disordered. The increased fluorescence intensity indicated that tryptophan and tyrosine were exposed which led an increase in hydrophobicity. In addition, the results of molecular dynamics (MD) simulations confirmed that the stability of OVA was reduced after PEF, which was related to the reduction of hydrogen bonding and the sharp fluctuation of aspartic acid. Therefore, PEF treatment induced the exposure of hydrophobic amino acids and the transformation of disulfide bond configuration which in turn masked or destroyed allergenic epitopes, and ultimately inhibited OVA allergenicity. This study provided insightful information for the production of hypoallergenic eggs and promoted the use of PEF techniques in the food field.

Structural characterization and calcium absorption-promoting effect of sucrose-calcium chelate in Caco-2 monolayer cells and mice

Sucrose emerges as a chelating agent to form a stable sucrose-metal-ion chelate that can potentially improve metal-ion absorption. This study aimed to analyze the structure of sucrose-calcium chelate and its potential to promote calcium absorption in both Caco-2 monolayer cells and mice. The characterization results showed that calcium ions mainly chelated with hydroxyl groups in sucrose to produce sucrose-calcium chelate, altering the crystal structure of sucrose (forming polymer particles) and improving its thermal stability. Sucrose-calcium chelate dose dependently increased the amount of calcium uptake, retention, and transport in the Caco-2 monolayer cell model. Compared to CaCl2 , there was a significant improvement in the proportion of absorbed calcium utilized for transport but not retention (93.13 ± 1.75% vs. 67.67 ± 7.55%). Further treatment of calcium channel inhibitors demonstrated the active transport of sucrose-calcium chelate through Cav1.3. Cellular thermal shift assay and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) assays indicated that the ability of sucrose-calcium chelate to promote calcium transport was attributed to its superior ability to bind with PMCA1b, a calcium transporter located on the basement membrane, and stimulate its gene expression compared to CaCl2 . Pharmacokinetic analysis of mice confirmed the calcium absorption-promoting effect of sucrose-calcium chelate, as evident by the higher serum calcium level (44.12 ± 1.90 mg/L vs. 37.42 ± 1.88 mmol/L) and intestinal PMCA1b gene expression than CaCl2 . These findings offer a new understanding of how sucrose-calcium chelate enhances intestinal calcium absorption and could be used as an ingredient in functional foods to treat calcium deficiency. PRACTICAL APPLICATION: The development of high-quality calcium supplements is crucial for addressing the various adverse symptoms associated with calcium deficiency. This study aimed to prepare a sucrose-calcium chelate and analyze its structure, as well as its potential to enhance calcium absorption in Caco-2 monolayer cells and mice. The results demonstrated that the sucrose-calcium chelate effectively promoted calcium absorption. Notably, its ability to enhance calcium transport was linked to its strong binding with PMCA1b, a calcium transporter located on the basement membrane, and its capacity to stimulate PMCA1b gene expression. These findings contribute to a deeper understanding of how the sucrose-calcium chelate enhances intestinal calcium absorption and suggest its potential use as an ingredient in functional foods for treating calcium deficiency.

High pressure-assisted enzymatic hydrolysis promotes the release of a bi-functional peptide from cowhide gelatin with dipeptidyl peptidase IV (DPP-IV) inhibitory and antioxidant activities

The process of generating functional peptides from cowhide gelatin is challenged by inefficient enzymatic hydrolysis. In this study, the researchers attempted to enhance the hydrolysis and potential functional properties of the peptides by subjecting the cowhide gelatin to high-pressure treatment (200, 300, and 400 MPa) for 20 min, followed by enzymatic hydrolysis. The highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, 2,2' azinobis(3 ethylbenzothiazoline 6 sulfonic acid) (ABTS) radical scavenging activity, and DPP-IV inhibitory activity of the hydrolysate were obtained at 200 MPa, accompanied with an increase in the content of hydrophobic, acidic, and basic amino acids (P < 0.05). Correspondingly, the high-pressure pretreatment (200 MPa) reduced the thermal stability, particle size, and morphological integrity of cowhide gelatin, with a corresponding increase in the exposure of hydrophobic regions. Altogether, these results indicated that appropriate high-pressure-assisted enzymatic hydrolysis reinforced the release of bi-functional peptides by modifying the structure of cowhide gelatin.

Novel Calcium-Binding Peptide from Bovine Bone Collagen Hydrolysates and Its Potential Pro-Osteogenic Activity via Calcium-Sensing Receptor (CaSR)

SCOPE

This paper aims to explore the osteogenic activity and potential mechanism of the peptide-calcium chelate, and provides a theoretical basis for peptide-calcium chelates as functional foods to prevent or improve osteoporosis.

METHODS AND RESULTS

In this research, a novel peptide (Phe-Gly-Leu, FGL) with a high calcium-binding capacity is screened from bovine bone collagen hydrolysates (CPs), calcium binding sites of which mainly included carbonyl, amino and carboxyl groups. The FGL-Ca significantly enhances the osteogenic activity of MC3T3-E1 cells (survival rate, differentiation, and mineralization). The results of calcium fluorescence labeling and molecular docking show that FGL-Ca may activate calcium-sensing receptor (CaSR), leading to an increase in intracellular calcium concentration, then enhancing osteogenic activity of MC3T3-E1 cells. Further research found that FGL-Ca significantly promotes the mRNA and protein expression levels of CaSR, transforming growth factor β (TGF-β1), TGF-β-type II receptor (TβRII), Smad2, Smad3, osteocalcin (OCN), alkaline phosphatase (ALP), osteoprotegrin (OPG), and collagen type I (COLI). Subsequently, in the signal pathway intervention experiment, the expression levels of genes and proteins related to the TGF-β1/Smad2/3 signaling pathway that are promoted by FGL-Ca are found to decrease.

CONCLUSIONS

These results suggest that FGL-Ca may activate CaSR, increase intracellular calcium concentration, and activate TGF-β1/Smad2/3 signaling pathway, which may be one of the potential mechanisms for enhancing osteogenic activity.

Phosphorylation modification of bovine bone collagen peptide enhanced its effect on mineralization of MC3T3-E1 cells via improving calcium-binding capacity

This study aimed to investigate the effect of phosphorylation modification of collagen peptide on its calcium-binding capacity and pro-mineralization activity. In this study, collagen peptide (Leu-Thr-Phe, LTF) and phosphorylated LTF (P-LTF) were synthesized and further chelated with calcium ions. The results showed that phosphorylation of LTF significantly enhanced its calcium-binding capacity. Spectra analysis revealed that the calcium-binding sites of P-LTF were mainly carbonyl, carboxyl, and phosphate groups. Molecular docking further demonstrated that the phosphate group introduced by phosphorylation enhanced the calcium-binding capacity of LTF by ionic bonds and coordination bonds. The stability analysis results suggested that intestinal fluid could repair the peptide-calcium complex destroyed by gastric fluid. The cell experiment displayed that P-LTF-Ca significantly improved the mineralization activity of MC3T3-E1 cells, and the order of effective influence was P-LTF-Ca > LTF-Ca > P-LTF > LTF. This study provided the theoretical basis for the potential application of phosphorylation modification in improving bone health.

Casein phosphopeptide calcium chelation: preparation optimization, in vitro gastrointestinal simulated digestion, and peptide fragment exploration

BACKGROUND

Calcium is important in the formation of bones and teeth, cell metabolism, and other physiological activities. In this work, casein phosphopeptide-calcium chelate (CPP-Ca) was synthesized and the optimal process parameters for the chelation reaction were obtained. The bioavailability of calcium in CPP-Ca was investigated by in vitro gastrointestinal simulated digestion. The existence of phytic acid and oxalic acid in the digestion system was evaluated to clarify the calcium holding ability of casein phosphopeptide (CPP). Liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used to identify oligopeptides from CPP-Ca.

RESULTS

The optimal process parameters for the chelation reaction were: peptide concentration 7.76 mgmL-1 , pH 8.54, and reaction temperature 43.3 °C. The digestion in vitro results indicated that the calcium release rate of CPP-Ca in the stomach for 2 h reached 85%, and about 50% of the ionized calcium was re-chelated with CPP in the intestine. Phytic acid and oxalic acid could lead to a sharp decrease in soluble calcium but around 50% of the calcium was still retained in the form of chelates in the presence of CPP. The LC-MS/MS identified 19 casein-derived oligopeptides after digestion, and calcium modifications were found on eight peptides derived from β-casein and αs2 -casein.

CONCLUSIONS

This study clarified the excellent calcium holding capacity of CPP in the presence of phytic acid and oxalic acid. Liquid chromatography-tandem mass spectrometry also revealed peptide changes, and identified peptides that chelate with calcium. These findings provided significant insights that could be relevant to the further utilization and product development of peptide-calcium chelate in the food industry. © 2023 Society of Chemical Industry.

Study on the Changes of Bone Calcium during the Fermentation of Bone Powders with Different Fermenters

Two fermenters, Lactobacillus acidophilus (LA) and the active dry yellow wine yeast (HY), were utilized to ferment cattle bones in order to release calcium. The influences of fermenters and the fermentation process on the calcium release capacity, particle properties, morphology, and chemical composition of bone powders were assessed, and the underlying mechanism was discussed. The results showed that LA had a better capacity of acid production than yeast, and therefore released more calcium during the fermentation of bone powders. The released calcium in the fermentation broth mainly existed in the forms of free Ca2+ ions, organic acid-bound calcium and a small amount of calcium-peptide chelate. For bone powders, the fermentation induced swollen bone particles, increased particle size, and significant changes of the internal chemical structure. Therefore, fermentation has a great potential in the processing of bone-derived products, particularly to provide new ideas for the development of calcium supplement products.

Preparation, characterization, and property evaluation of Hericium erinaceus peptide-calcium chelate

Recently, owing to the good calcium bioavailability, peptide-calcium chelates made of various foods have been emerging. Hericium erinaceus, an edible fungus, is rich in proteins with a high proportion of calcium-binding amino acids. Thus, mushrooms serve as a good source to prepare peptide-calcium chelates. Herein, the conditions for hydrolyzing Hericium erinaceus peptides (HP) with a good calcium-binding rate (CBR) were investigated, followed by the optimization of HP-calcium chelate (HP-Ca) preparation. Furthermore, the structure of the new chelates was characterized along with the evaluation of gastrointestinal stability and calcium absorption. Papain and a hydrolysis time of 2 h were selected for preparing Hericium erinaceus peptides, and the conditions (pH 8.5, temperature 55°C, time 40 min, and mass ratio of peptide/CaCl2 4:1) were optimal to prepare HP-Ca. Under this condition, the chelates contained 6.79 ± 0.13% of calcium. The morphology and energy disperse spectroscopy (EDS) analysis showed that HP-Ca was loose and porous, with an obvious calcium element signal. The ultraviolet-visible (UV) absorption and Fourier transform infrared spectroscopy (FT-IR) analysis indicated that calcium possibly chelates to HP via interaction with free -COO- from acidic amino acids and C = O from amide. HP-Ca displayed good stability against stimulated gastrointestinal digestion. Moreover, HP-Ca significantly improved the calcium absorption by Caco-2 epithelial cells. Thus, HP-Ca is a promising Ca supplement with high calcium bioavailability.

A critical review of a typical research system for food-derived metal-chelating peptides: Production, characterization, identification, digestion, and absorption

In the past decade, food-derived metal-chelating peptides (MCPs) have attracted significant attention from researchers working towards the prevention of metal (viz., iron, zinc, and calcium) deficiency phenomenon by primarily inhibiting the precipitation of metals caused by the gastrointestinal environment and exogenous substances (including phytic and oxalic acids). However, for the improvement of limits of current knowledge foundations and future investigation directions of MCP or their derivatives, several review categories should be improved and emphasized. The species' uniqueness and differences in MCP productions highly contribute to the different values of chelating ability with particular metal ions, whereas comprehensive reviews of chelation characterization determined by various kinds of technique support different horizons for explaining the chelation and offer options for the selection of characterization methods. The reviews of chelation mechanism clearly demonstrate the involvement of potential groups and atoms in chelating metal ions. The discussions of digestive stability and absorption in various kinds of absorption model in vitro and in vivo as well as the theory of involved cellular absorption channels and pathways are systematically reviewed and highlighted compared with previous reports as well. Meanwhile, the chelation mechanism on the molecular docking level, the binding mechanism in amino acid identification level, the utilizations of everted rat gut sac model for absorption, and the involvement of cellular absorption channels and pathway are strongly recommended as novelty in this review. This review makes a novel contribution to the literature by the comprehensive prospects for the research and development of food-derived mineral supplements.

Preparation, Structural Characterization, and Stability of Low-Molecular-Weight Collagen Peptides-Calcium Chelate Derived from Tuna Bones

This study was conducted to prepare calcium chelate of low-molecular-weight tuna bone collagen peptides (TBCPLMW) with a high chelation rate and to identify its structural characteristics and stability. The optimum conditions for calcium chelation of TBCPLMW (TBCPLMW-Ca) were determined through single-factor experiments and response surface methodology, and the calcium-chelating capacity reached over 90% under the optimal conditions. The amino acid compositions implied that Asp and Glu played important roles in the formation of TBCPLMW-Ca. Structural characterizations determined via spectroscopic analyses revealed that functional groups such as -COO-, N-H, C=O, and C-O were involved in forming TBCPLMW-Ca. The particle size distributions and scanning electron microscopy results revealed that folding and aggregation of peptides were found in the chelate. Stability studies showed that TBCPLMW-Ca was relatively stable under thermal processing and more pronounced changes have been observed in simulated gastric digestion, presumably the acidic environment was the main factor causing the dissociation of the TBCPLMW-Ca. The results of this study provide a scientific basis for the preparation of a novel calcium supplement and is beneficial for comprehensive utilization of tuna bones.

Purification, Identification, Chelation Mechanism, and Calcium Absorption Activity of a Novel Calcium-Binding Peptide from Peanut (Arachis hypogaea) Protein Hydrolysate

A novel calcium-binding peptide was purified from peanut protein hydrolysate using gel filtration chromatography and identified using HPLC-MS/MS. Its amino acid sequence was determined as Phe-Pro-Pro-Asp-Val-Ala (FPPDVA, named as FA6) with the calcium-binding capacity of 15.67 ± 0.39 mg/g. Then, the calcium chelating characteristics of FPPDVA were investigated using ultraviolet-visible absorption spectroscopy, fluorescence spectroscopy, Fourier transform infrared spectroscopy, particle size, and zeta potential. The results showed that FPPDVA interacted with calcium ions, the chelation of calcium ions induced FPPDVA to fold and form a denser structure, the calcium-binding sites may mainly involve oxygen atoms from the carboxyl residues of Asp and Ala, and Phe possessed contact energy and carbonyl residues of Val. Microstructure analysis showed that FPPDVA-calcium chelate exhibited a regularly ordered and tightly aggregated sheets or block structures. Additionally, FPPDVA-calcium chelate had good gastrointestinal digestive stability and thermal stability. The results of everted rat intestinal sac and Caco-2 cell monolayer experiments showed that FPPDVA-calcium chelate could promote calcium absorption and transport through the Cav1.3 and TRPV6 calcium channels. These data suggest that FPPDVA-calcium chelate possesses the potential to be developed and applied as calcium supplement.

Improving adsorption performance of L-ascorbic acid from aqueous solution using magnetic rice husk as an adsorbent: experimental and RSM modeling

In this research, rice husk (RH) was utilized to prepare a magnetic adsorbent for adsorption of ascorbic acid (AA). The magnetic agent is iron(III) chloride (FeCl₃). The impact of acid concentration in the range of 400-800 ppm, adsorbent dosage in the range of 0.5-1 g, and contact time in the range of 10-130 min were studied. The Langmuir model had the highest R² of 0.9982, 0.9996, and 0.9985 at the temperature of 15, 25, and 35 °C, respectively, and the q_max values in these temperatures have been calculated at 19.157, 31.34, and 38.75 mg/g, respectively. The pseudo-second-order kinetic model had the best agreement with the experimental results. In this kinetic model, the values of q have been measured at 36.496, 45.248, and 49.019 mg/g at the acid concentration of 418, 600, and 718 ppm, respectively. The values of ΔH^o and ΔS^o were measured 31.972 kJ/mol and 120.253 kJ/mol K, respectively, which proves the endothermic and irregularity nature of the adsorption of AA. Besides, the optimum conditions of the design-expert software have been obtained 486.929 ppm of acid concentration, 0.875 g of the adsorbent dosage, and 105.397 min of the contact time, and the adsorption efficiency in these conditions was determined at 92.94%. The surface area of the RH and modified RH was determined of 98.17 and 120.23 m²/g, respectively, which confirms the high surface area of these two adsorbents.

Effects of casein phosphopeptides on thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate

This study aimed to elucidate the effect of casein phosphopeptides (CPP) on the thermal stability and sensory quality of whey protein emulsions containing calcium beta-hydroxy-beta-methylbutyrate (WPEs-HMB-Ca). The interaction mechanism among CPP, HMBCa, and WP in the emulsions before and after autoclaving (121 °C, 15 min) was systematically investigated from macroscopic external and microscopic molecular perspectives. It was found that WPEs-HMB-Ca treated by autoclaving resulted in an increase in droplet size (d4,3 = 24.09 μm) due to aggregation/flocculation of proteins, along with a stronger odor with higher viscosity, compared to those without autoclaving. When CPP:HMB-Ca = 1:25 (w/w) in the emulsion, the droplets exhibited a more uniform and consistent state in the emulsion. In addition, CPP was able to inhibit the formation of complex spatial network structures of proteins during autoclaving by binding with Ca2+, thus improving the thermal stability and storage stability of WPEs-HMB-Ca. This work might provide theoretical guidance for developing functional milk drinks with good thermal stability and flavor.

Novel iron-chelating peptide from egg yolk: Preparation, characterization, and iron transportation

In this work, an egg yolk protein hydrolysate (EYPH) with a high iron-chelating ability (87.32%) was prepared. The fractionation using 60% (v/v) ethanol concentration (E3 fraction) led to the efficiently accumulating the iron-chelating peptides in EYPH. The characterization results showed that iron mainly chelated with carboxyl, amino and phosphate groups of peptides. From E3 fraction, six iron-chelating peptides with MW ranging from 1372.36 to 2937.04 Da were identified and a hypothesized molecular model of DDSSSpSpSpSpSpSVLSK-Fe was simulated. In vitro stability determination showed that E3-Fe chelate owned a good heat, alkalinity and digestion tolerance, but a relatively bad acid tolerance. Finally, iron transport analysis showed that iron in the E3-Fe would be absorbed in caco-2 cell membrane more effectively than that of iron salts, indicating that it was possible to apply the E3-Fe complex as iron supplements.

Metal-binding peptides and their potential to enhance the absorption and bioavailability of minerals

Minerals including calcium, iron, zinc, magnesium, and copper have several human nutritional functions due to their metabolic activities. Body tissues require sufficient levels of a variety of micronutrients to maintain their health. To achieve these micronutrient needs, dietary consumption must be adequate. Dietary proteins may regulate the biological functions of the body in addition to acting as nutrients. Some peptides encoded in the native protein sequences are primarily responsible for the absorption and bioavailability of minerals in physiological functions. Metal-binding peptides (MBPs) were discovered as potential agents for mineral supplements. Nevertheless, sufficient studies on how MBPs affect the biological functions of minerals are lacking. The hypothesis is that the absorption and bioavailability of minerals are significantly influenced by peptides, and these properties are further enhanced by the configuration and attribute of the metal-peptide complex. In this review, the production of MBPs is discussed using various key parameters such as the protein sources and amino acid residues, enzymatic hydrolysis, purification, sequencing and synthesis and in silico analysis of MBPs. The mechanisms of metal-peptide complexes as functional food ingredients are elucidated, including metal-peptide ratio, precursors and ligands, complexation reaction, absorbability and bioavailability. Finally, the characteristics and application of different metal-peptide complexes are also described.

A novel calcium-binding peptide from bovine bone collagen hydrolysate and chelation mechanism and calcium absorption activity of peptide-calcium chelate

A novel calcium-binding peptide from bovine bone collagen hydrolysate was screened based on a new target-the calcium-sensing receptor (CaSR), and its chelation mechanism and calcium absorption activity were investigated. Glu-Tyr-Gly exhibited superior binding affinities to CaSR because of its interaction with the active sites of the CaSR Venus Flytrap (VFT) domain. Glu-Tyr-Gly-Ca may exist in five potential chelation modes and its potential chelation mechanism was that calcium ions were located in the center and surrounded by ionic bonds (carboxyl group) and coordination bonds (carbonyl, amino, and carboxyl group). Glu-Tyr-Gly-Ca was slightly damaged in the intestinal fluid and at different temperatures, whereas it was severely damaged in the gastric fluid and acidic conditions. The results of the calcium dialysis percentage and Caco-2 cells experiments showed that Glu-Tyr-Gly-Ca possessed good calcium transport activity and bioavailability. The findings provided theoretical basis for Glu-Tyr-Gly-Ca as potential calcium supplement to improve intestinal calcium absorption.

Preparation of quinoa bran dietary fiber-based zinc complex and investigation of its antioxidant capacity in vitro

In order to improve the economic utilization of quinoa bran and develop a safe and highly available zinc ion biological supplement. In this study, a four-factor, three-level response surface optimization of quinoa bran soluble dietary fiber (SDF) complexation of zinc was studied. The effect used four factors on the chelation rate was investigated: (A) mass ratio of SDF to ZnSO₄.7H₂O, (B) chelation temperature, (C) chelation time, and (D) pH. Based on the results of the single-factor test, the four-factor three-level response surface method was used to optimize the reaction conditions. The optimal reaction conditions were observed as mentioned here: the mass ratio of quinoa bran SDF to ZnSO₄.7H₂O was 1, the reaction temperature was 65°C, the reaction time was 120 min, and the pH of the reaction system was 8.0. The average chelation rate was 25.18%, and zinc content is 465.2 μg/g under optimal conditions. The hydration method rendered a fluffy quinoa bran SDF structure. The intramolecular functional groups were less stable which made the formation of the lone pairs of electrons feasible to complex with the added divalent zinc ions to form a quinoa bran soluble dietary fiber-zinc complex [SDF-Zn(II)]. The SDF-Zn(II) chelate had higher 2,2-diphenylpicrylhydrazyl (DPPH), ABTS⁺, hydroxyl radical scavenging ability, and total antioxidant capacity. Therefore, metal ion chelation in dietary fiber is of biological importance.

Food-derived bioactive peptides as momentous food components: Can functional peptides passed through the PI3K/Akt/mTOR pathway and NF-κB pathway to repair and protect the skeletal muscle injury?

Muscle injury is defined as an overuse injury or traumatic distraction of a muscle, which is latent in any sport event, from amateur to large events. Based on previous numbers of muscle injuries and time spent to the athletes' recovery, the use of dietary functional factors intervention strategies is essential to enhance the recovery process and health. In recent years, there has been increasing evidence that biologically active peptides played an important role in sports nutrition and muscle injure recovery. Food-derived bioactive peptides were physiologically active peptides mostly derived from proteins following hydrolysis, which could be resorbed in intact form to reduce muscle damage following exercise and induce beneficial adaptions within the connective tissue. However, the complexity of the histoarchitectural considerations for skeletal muscle injuries and the repair mechanism of damaged skeletal muscle were not well known. In the following overview, the potential mechanisms and possible limitations regarding the damaged skeletal muscle metabolism were summarized, which aimed to present an overview of the nutritional strategies and recommendations after a muscular sports injury, emphasizing the use of main bioactive peptides. In addition, this review will provide implications for the studies of dietary bioactive peptides in the future.

Effects of ultrasound on the structural and functional properties of sheep bone collagen

The study evaluated the effect of an ultrasound-assisted treatment on the structural and functional properties of sheep bone collagen (SBC). The type and distribution of SBC were analyzed by proteome (shotgun) technology combined with liquid chromatography-tandem mass spectrometry. Compared with pepsin extraction, the ultrasound-assisted treatment significantly increased the collagen extraction rate by 17.4 pp (P < 0.05). The characteristic functional groups and structural integrity of collagen extracted by both methods were determined via Fourier transform infrared spectroscopy, ultraviolet absorption spectroscopy, and fluorescence spectroscopy. Circular dichroism spectra revealed that the ultrasound-assisted pretreatment reduced α-helix content by 1.6 pp, β-sheet content by 21.9 pp, and random coils content by 28.4 pp, whereas it increased β-turn content by 51.9 pp (P < 0.05), compared with pepsin extraction. Moreover, ultrasound-assisted treatment collagen had superior functional properties (e.g., solubility, water absorption, and oil absorption capacity) and foaming and emulsion properties, compared with pepsin extraction. Furthermore, the relative content of type I collagen in ultrasound-assisted extracted SBC was highest at 79.66%; only small proportions of type II, VI, X, and XI collagen were present. Peptide activity analysis showed that SBC had potential antioxidant activity, dipeptidyl peptidase 4 inhibitory activity, and angiotensin-converting enzyme inhibitory activity; it also had anticancer, antihypertensive, anti-inflammatory, and immunomodulatory effects.

Process Optimization, Structural Characterization, and Calcium Release Rate Evaluation of Mung Bean Peptides-Calcium Chelate

To reduce grievous ecological environment pollution and protein resource waste during mung bean starch production, mung bean peptides-calcium chelate (MBP-Ca) was synthesized as a novel and efficient calcium supplement. Under the optimal conditions (pH = 6, temperature = 45 °C, mass ratio of mung bean peptides (MBP)/CaCl₂ = 4:1, MBP concentration = 20 mg/mL, time = 60 min), the obtained MBP-Ca achieved a calcium chelating rate of 86.26%. MBP-Ca, different from MBP, was a new compound rich in glutamic acid (32.74%) and aspartic acid (15.10%). Calcium ions could bind to MBP mainly through carboxyl oxygen, carbonyl oxygen, and amino nitrogen atoms to form MBP-Ca. Calcium ions-induced intra- and intermolecular interactions caused the folding and aggregation of MBP. After the chelation reaction between calcium ions and MBP, the percentage of β-sheet in the secondary structure of MBP increased by 1.90%, the size of the peptides increased by 124.42 nm, and the dense and smooth surface structure of MBP was transformed into fragmented and coarse blocks. Under different temperatures, pH, and gastrointestinal simulated digestion conditions, MBP-Ca exhibited an increased calcium release rate compared with the conventional calcium supplement CaCl₂. Overall, MBP-Ca showed promise as an alternative dietary calcium supplement with good calcium absorption and bioavailability.