Preparation, characterization and calcium release evaluation in vitro of casein phosphopeptides-soluble dietary fibers copolymers as calcium delivery system

Construction and characterization of Zn-WPH-COS complex nanoparticles with improved zinc bioavailability

Precipitation was an important obstacle to improving zinc's bioavailability. Therefore, zinc-whey protein hydrolysate-chitosan oligosaccharide (Zn-WPH-COS) complexes (167 nm) were prepared by linking Zn-WPH (zinc: 18.4%) with COS (1:1, 2 h) to enhance zinc's bioaccessibility. Fourier-transform infrared showed Zn-WPH formed with zinc replaced hydrogen (from 3274 to 3279 cm-1) and reacted with COO- (C-N: from 1394 to 1402 cm-1), a new peak at 1025 cm-1 proved COS can be successful cross-linked (Zn-WPH-COS). Fluorescence spectra showed zinc and COS reduced WPH hydrophobicity (28.0 and 39.0%, respectively). Circular dichroism showed zinc decreased WPH α-helix (from 13.7 to 11.5%), in contrast with COS to Zn-WPH. Zinc solubility and dialyzability were increased (64.5/ 54.2% vs 50.2/ 41.2% vs 29.5/ 21.7%) in Zn-WPH-COS, compared with Zn-WPH and ZnSO4·7H2O, respectively, due to the smallest size (167 nm) and COS protection on Zn-WPH (gastric digestion). These results indicate Zn-WPH-COS could significantly improve the digestion and absorption of zinc.

Characterization and in vitro calcium release of the novel calcium-loaded complexes using Antarctic krill protein and pectin: Effect of different blending sequences

Food-grade biopolymer-based complexes are of particular interest in the field of biologic ingredient delivery owing to unique controlled-release properties. Herein, three calcium-loaded complexes using Antarctic krill protein (P) and pectin (HMP) with different blending sequences were designed, named P + Ca + HMP, P + HMP + Ca and HMP + Ca + P, respectively. The calcium-loaded capacity, structural properties, and in vitro gastrointestinal calcium release of the complexes were investigated. The results demonstrated that the calcium binding rate and content of the P + Ca + HMP complex were the highest, reaching to 90.3 % and 39.0 mg/g, respectively. Particularly, the P + Ca + HMP complex exhibited a more stable fruit tree-like structure. Furthermore, the structural analysis confirmed that the primary interaction forces involved hydrogen bond, electrostatic, hydrophobic and ionic bond interaction. Ultimately, the P + Ca + HMP complex demonstrated superior calcium delivery. In conclusion, a novel calcium delivery system was successfully developed based on optimized the self-assembly sequence, which held significant importance in promoting the high-value utilization of Antarctic krill protein and enhancing the in vitro bioaccessibility of calcium.

The application of ferritin in transporting and binding diverse metal ions

The ferritin cage can not only load iron ions in its inner cavity, but also has the capacity to carry other metal ions, thus constructing a new biological nano-transport system. The nanoparticles formed by ferritin and minerals can be used as ingredients of mineral supplements, which overcome the shortcomings of traditional mineral ingredients such as low bioavailability. Moreover, ferritin can be used to remove heavy metal ions from contaminated food. Silver and palladium nanoparticles formed by ferritin are also applied as anticancer agents. Ferritin combined with metal ions can be also used to detect harmful substances. This review aims to provide a comprehensive overview of ferritin's function in transporting and binding metal ions, and discusses the limitations and future prospects, which offers valuable insights for the application of ferritin in mineral supplements, food detoxifiers, anticancer agents, and food detections.

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.

Characteristics and osteogenic mechanism of glycosylated peptides-calcium chelate

Finding effective practical components to promote bone mineralization from the diet has become an effective method to regulate bone mass. In this study, peptides-calcium chelate derived from Crimson Snapper scales protein hydrolysates (CSPHs), and xylooligosaccharide (XOS)-peptides-calcium chelate prepared by transglutaminase (TGase) pathway, named CSPHs-Ca and XOS-CSPHs-Ca-TG, were used to explore the effects of glycosylation on their structural properties and osteogenic activity in vitro. Results showed that XOS-CSPHs-Ca-TG had better calcium phosphate crystallization inhibition activity with more unified structures than CSPHs-Ca, and could effectively maintain a stable calcium content in the gastrointestinal tract. Meanwhile, the glycosylated peptide-calcium chelate could accelerate the calcium transport efficiency in the Caco-2 cell monolayer, up to 3.54 folds of the control group. Moreover, XOS-CSPHs-Ca-TG exhibited prominent osteogenic effects by promoting the proliferation of MC3T3-E1 cells, increasing the secretion of osteogenic related factors, and accelerating the formation of intracellular mineralized nodules. RT-qPCR results further confirmed that this beneficial effect of XOS-CSPHs-Ca-TG was achieved by activating the Wnt/β-catenin signaling pathway. These results suggested that glycosylation might be a promising method for optimizing structural properties and osteogenic activity of peptide-calcium chelate.

Casein phosphopeptide-calcium chelate: Preparation, calcium holding capacity and simulated digestion in vitro

In this work, CPP-Ca chelate was synthesized by chelating casein phosphopeptide (CPP) and calcium and characterized by Fourier transform infrared spectroscopy (FTIR), Scanning electron microscopy (SEM) Energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The antioxidant activity and calcium holding capacity of CPP-Ca were evaluated and its secondary structure transition was monitored during gastrointestinal digestion by in situ Raman spectroscopy. The results demonstrated that calcium chelating rate reached 40 % and calcium ion was bound to CPP mainly through the interaction of carboxyl and amino groups. The result of calcium holding capacity confirmed the formation of calcium phosphate precipitates could be delayed by 10-15 min with increasing CPP concentration. In vitro simulated digestion revealed CPP-Ca exhibited excellent calcium solubility and its secondary structural changes occurred, especially α-helix and β-sheet content. These findings provided significant insights into enhancing bioavailability of calcium supplements and developing of calcium functional foods for human and animals.

A comprehensive review on preparation, structure-activities relationship, and calcium bioavailability of casein phosphopeptides

Calcium is one of the important elements for human health. Calcium deficiencies can lead to numerous diseases. Calcium chelating peptides have shown potential application in the management of calcium deficiencies. Casein phosphopeptides (CPP) are phosphoseryl-containing fragments of casein by enzymatic hydrolysis or fermentation during manufacture of milk products as well as during intestinal digestion. An increasing number of CPP with the ability to facilitate and enhance the bioavailability of calcium are being discovered and identified. In this review, 249 reported CPP derived from four types of bovine casein (αs1, αs2, β and κ) were collected, and the amino acid sequence and phosphoserine group information were sorted out. This review outlines the current enzyme hydrolysis, detection methods, purification, structure-activity relationship and mechanism of intestinal calcium absorption in vitro and in vivo as well as application of CPP.

Antidiabetic bio-peptides of soft and hard wheat glutens

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Effect of enzyme purification techniques on kiwifruit extract and gluten peptides were investigated.

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Ammonium sulfate was the most efficient kiwifruit enzyme purification method.

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Ammonium sulfate based purified enzyme produced bio-active peptides (<1 kDa).

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The highest in vitro inhibitory activities was observed on gliadin based peptides.

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High Pro, Ser, and Asp contents of sub-fraction (P3) explain the inhibitory effects.

The effects of various purification techniques on kiwifruit enzyme characteristics (protease activity, kinetic parameters, and protein patterns) and production of wheat gluten bio-active peptides were investigated. The enzyme extract purified by ammonium sulfate precipitation method exhibited the highest protease activity (26), K_m (0.04 ± 0.002 mM), K_cat/K_m (40), and yield (96%). Using actinidin, the hard and soft wheat gluten subunit proteins produced antidiabetic inhibitory (α-glucosidase and α-amylase) peptides. The smallest M_w fraction of soft wheat gliadin peptide (<1 kDa) showed the highest inhibitory capacity against α-glucosidase (18.4 ± 0.7%) and α-amylase (53.3 ± 1.9%). The presence of high levels of amino acids with hydroxyl groups and proline in P3 sub-fraction had a critical role on α-glucosidase (47.2%) and α-amylase (71.2%) inhibitory activities. In conclusion, wheat gluten subunit peptides showed significant metabolic effects relevant to glucose and insulin control in vitro.

Preparation of corn ACE inhibitory peptide-ferrous chelate by dual-frequency ultrasound and its structure and stability analyses

In order to improve iron chelating ability and retain the activity of functional peptide, corn peptide was chelated with iron to form corn ACE inhibitory peptide-ferrous chelate (CP-Fe) treated by dual-frequency ultrasound. Furthermore, the chelating mechanism was revealed by analyzing various structural changes, and the stability was further evaluated. Under this study condition, the iron-binding capacity of corn ACE inhibitory peptide (CP) and chelate yield reached 66.39% and 82.87%, respectively. Ultrasound-treated CP exhibited a high iron chelating ability, meanwhile, chelation reaction had no significant effect on the ACE inhibition activity (82.21%) of the peptide. CP-Fe was formed by binding the peptides amino, carbonyl and carboxyl groups with Fe²⁺ demonstrated by Ultra-violet spectroscopy, Fourier transform infrared characterization, X-ray diffraction, energy dispersion spectrum, zeta potential, amino acid composition and other multi-angle analyses. Moreover, ultrasound-treated CP-Fe chelate exhibited porous surface and uniform nanoparticle shape. Furthermore, ultrasound-treated CP-Fe chelate exhibited an excellent stability towards various pH (retention rate ≥ 95.47% at pH 6-10), temperatures (retention rate ≥ 85.10% at 25-70 °C), and gastrointestinal digestion (retention rate 79.18%). Overall, ultrasound-treated CP-Fe chelate possessed high iron-chelating ability, ACE inhibition activity and stability. This study provides a novel synthesis method of the iron-chelating corn ACE inhibitory peptide, which is promising to be applied as iron supplements with high efficiency, bioactivity, and stability.

Sources, chemical synthesis, functional improvement and applications of food-derived protein/peptide-saccharide covalent conjugates: a review

Proteins/peptides and saccharides are two kinds of bioactive substances in nature. Recently, increasing attention has been paid in understanding and utilizing covalent interactions between proteins/peptides and saccharides. The products obtained through covalent conjugation of proteins/peptides to saccharides are shown to have enhanced functional attributes, such as better gelling property, thermostability, and water-holding capacity. Additionally, food-derived protein/peptide-saccharide covalent conjugates (PSCCs) also have biological activities, such as antibacterial, antidiabetic, anti-osteoporosis, anti-inflammatory, anti-cancer, immune regulatory, and other activities that are widely used in the functional food industry. Moreover, PSCCs can be used as packaging or delivery materials to improve the bioavailability of bioactive substances, which expands the development of food-derived protein and saccharide resources. Thus, this review was aimed to first summarize the current status of sources, classification structures of natural PSCCs. Second, the methods of chemical synthesis, reaction conditions, characterization and reagent formulations that improve the desired functional characteristics of food-derived PSCCs were introduced. Third, functional properties such as emulsion, edible films/coatings, and delivery of active substance, bio-activities such as antioxidant, anti-osteoporosis, antidiabetic, antimicrobial of food-derived PSCCs were extensively discussed.

Fabrication of a ferritin-casein phosphopeptide-calcium shell-core composite as a novel calcium delivery strategy

Plant ferritin has a natural cage-like nanospace for carrying bioactive ingredients. By taking advantage of the calcium binding ability of casein phosphopeptide (CPP) and the cage-like conformation of plant ferritin, a ferritin-CPP shell-core complex (FC) was fabricated with the reversible self-assembly character of ferritin induced by a pH 2.0/7.0 transition strategy. The FC-calcium composite (FCC) was further fabricated by binding of the FC with calcium ions. When the same amount of calcium was loaded, the calcium binding capacity of the FCC was 28.13 ± 1.65%, which was significantly higher than that of ferritin and CPP alone. Fluorescence and Fourier transform infrared analysis indicated that the CPP encapsulation and the calcium binding in the FCC influenced the ferritin structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) results showed that the spherical morphology and the 12 nm-diameter size were sustained in the FC and FCC. Moreover, the FCC as a transport carrier could increase the precipitation time of calcium phosphate, and the encapsulated calcium could be released in a more sustained manner as compared with ferritin and CPP under simulated in vitro gastrointestinal conditions. This study presents a novel calcium delivery strategy based on the ferritin cage and CPP, which will improve the applicability of ferritin and CPP and enhance the bioavailability of calcium ions.

Preparation of dextran-casein phosphopeptide conjugates, evaluation of its calcium binding capacity and digestion in vitro

In order to construct a novel and efficient calcium delivery system, a dextran- casein phosphopeptide (CPP) conjugates as calcium carrier was prepared by Maillard reaction of CPP and dextran. The preparation of the conjugates, construction of calcium delivery system and digestion in vitro were studied. The grafting rate of conjugates, which was confirmed by migration and intensity changes in the characteristic peaks using ultraviolet-visible and Fourier transform infrared spectroscopy, reached 48.88%. The microscopy showed CPP was coated with dextran, the conjugates with a kind of "shell-core" structure had excellent stability. Compared with CPP, the chelating rate of conjugates increased from 6.0% to 13.87%, and the calcium retention rate improved from 1.09% to 7.90% in vitro digestion. The calcium binding capacity and effect of controlled release of the conjugates were superior to those of CPP. Therefore, the conjugates could be used as an effective carrier for new calcium supplements.

Chicken foot broth byproduct: A new source for highly effective peptide-calcium chelate

As a means of adding value, chicken foot broth byproduct can be processed to obtain calcium and bioactive peptides from the separated bones and meat residues. In this study, cleaned, dried, and powdered bones yielded 31.4 ± 0.6% calcium content. The meat residues were hydrolyzed to obtain over a hundred distinctive peptides, which were analyzed using LC-MS/MS and the SpirPep web-based tool. The peptides were rich in Glu, Asp, Lys, Gly and Leu, and also exhibited diverse bioactivities, among them primarily inhibition of dipeptidyl peptidase IV and angiotensin-converting enzyme. Calcium chelation assay determined the peptides to bind calcium at 235.7 ± 20.0 mg/g peptide-calcium chelate. Caco-2 cells treated with the chelate at calcium concentrations of 0-10 mM exhibited enhanced absorption relative to CaCl₂. This demonstrates that calcium and chelating peptides generated from the same byproduct can produce peptide-calcium chelate, a potential ingredient in functional foods.

Bioavailability of nanotechnology-based bioactives and nutraceuticals

Bioaccessibility and bioavailability of some hydrophobic bioactives (e.g., carotenoids, polyphenols, fat-soluble vitamins, phytosterols and fatty acids) are limited due to their low water solubility, and in some instances low chemical stability. Nanotechnology involving nanometric (r<500nm) delivery systems, can be used to improve the solubility and thus enhance the bioaccessibility and bioavailability of hydrophobic compounds. Nanometric delivery systems, derived from food grade phospholipids and biopolymers adopt many forms, including liposomes, micelles, micro/nanoemulsions, particles, polyelectrolyte complexes, and hydrogels. The small particle sizes and customized materials used to create delivery systems confer their unique properties such as higher stability and/or resistance to enzymatic activity in the gastrointestinal tract. This chapter provides an overview of bioaccessibility and bioavailability of different classes of hydrophobic bioactive compounds, focusing on nanometric delivery systems and methods of evaluation.

Role of polysaccharide conjugation in physicochemical and emulsifying properties of egg phosvitin and the calcium binding capacity of its phosphopeptides

Glycosylation with pectin simultaneously improved the emulsifying properties of egg phosvitin and the calcium binding capacity of its phosphopeptides.