The preparation of Fe-glycine complexes by a novel method (pulsed electric fields)

Preparation, structural and morphological characterization of cartilage type II collagen peptide assemblies from sturgeon head

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.

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.

Carbon Quantum Dots from Roasted Coffee Beans: Their Degree and Mechanism of Cytotoxicity and Their Rapid Removal Using a Pulsed Electric Field

Carbon quantum dots (CQDs) from heat-treated foods show toxicity, but the mechanisms of toxicity and removal of CQDs have not been elucidated. In this study, CQDs were purified from roasted coffee beans through a process of concentration, dialysis and lyophilization. The physical properties of CQDs, the degree and mechanism of toxicity and the removal method were studied. Our results showed that the size of CQDs roasted for 5 min, 10 min and 20 min were about 5.69 ± 1.10 nm, 2.44 ± 1.08 nm and 1.58 ± 0.48 nm, respectively. The rate of apoptosis increased with increasing roasting time and concentration of CQDs. The longer the roasting time of coffee beans, the greater the toxicity of CQDs. However, the caspase inhibitor Z-VAD-FMK was not able to inhibit CQDs-induced apoptosis. Moreover, CQDs affected the pH value of lysosomes, causing the accumulation of RIPK1 and RIPK3 in lysosomes. Treatment of coffee beans with a pulsed electric field (PEF) significantly reduced the yield of CQDs. This indicates that CQDs induced lysosomal-dependent cell death and increased the rate of cell death through necroptosis. PEF is an effective way to remove CQDs from roasted coffee beans.

Combination with litchi procyanidins under PEF treatment alters the physicochemical and processing properties of inulin

A novel alternative to prepare the inulin-procyanidin complex assisted by pulsed electric field (PEF) treatment was explored in this study. Results showed that the optimal condition of PEF treatment enhanced the adsorption rate of procyanidins to inulin from 78.56 to 103.46 μg/mg. Based on well fitted by Redlich-Peterson model and spectral analysis including UV and FT-IR, the interaction between inulin and procyanidin was evidenced to be dominated by hydrogen bonds. The DSC curve and the SEM spectrum displayed better stability of the PEF-treated inulin-procyanidin complex than the untreated complex. The PEF-treated complex had lower solubility but higher water-holding capacity than inulin, which exhibited stronger shear-thinning property and more stable flow behavior referring to rheological analysis. Furthermore, the gel formed from the PEF-treated complex possessed greater hardness, chewiness and viscosity, with no significant effects noted in terms of springiness, cohesiveness and resilience.

Advances in pulsed electric stimuli as a physical method for treating liquid foods

There is a need for alternative technologies that can deliver safe and nutritious foods at lower costs as compared to conventional processes. Pulsed electric field (PEF) technology has been utilised for a plethora of different applications in the life and physical sciences, such as gene/drug delivery in medicine and extraction of bioactive compounds in food science and technology. PEF technology for treating liquid foods involves engineering principles to develop the equipment, and quantitative biochemistry and microbiology techniques to validate the process. There are numerous challenges to address for its application in liquid foods such as the 5-log pathogen reduction target in food safety, maintaining the food quality, and scale up of this physical approach for industrial integration. Here, we present the engineering principles associated with pulsed electric fields, related inactivation models of microorganisms, electroporation and electropermeabilization theory, to increase the quality and safety of liquid foods; including water, milk, beer, wine, fruit juices, cider, and liquid eggs. Ultimately, we discuss the outlook of the field and emphasise research gaps.

Are Citric Acid-Iron II Complexes True Chelates or Just Physical Mixtures and How to Prove This?

Although mineral chelates are widely produced to be used as food fortifiers, the proof that these complexes are chelates is still missing. In our present work, iron II complexes using citric acid in different ratios are produced, and the occurrence of chelation is investigated along with its behavior according to a molar ratio between the ligand and the mineral. High performance liquid chromatography (HPLC), flame atomic absorption spectroscopy (FAAS), ultraviolet-visible spectroscopy (UV-Vis), Fourier-transform infrared (FTIR), and near infrared spectroscopy (NIR) were used for a non-structural characterization of these complexes. In contrast to published work, our findings show that the chelation of citric acid is achieved in the liquid form and at a low pH and that the molar ratio is very important in setting the direction of the reaction, either toward chelation or dimer formation. The ratio citric acid:iron 1:4 seems to be the most convenient ratio in which no free citric acid remains in the solution, while the 1:3 ratio behaves differently, requiring further investigations by such techniques as extended X-ray absorption fine structure spectroscopy (EXAFS), among others, in order to deeply identify the structural organization occurring in this ratio. NIR, extensively used in industries, proved to be very useful in the demonstration and characterization of chelates. These findings are particularly advantageous for pharmaceutical and food industries in offering an innovative competent fortifying agent to be used in combatting iron deficiency.

Potential applications of pulsed electric field in the fermented wine industry

Fermented wine refers to alcoholic beverages with complex flavor substances directly produced by raw materials (fruit or rice) through microbial fermentation (yeast and bacteria). Its production steps usually include saccharification, fermentation, filtration, sterilization, aging, etc., which is a complicated and time-consuming process. Pulsed electric field (PEF) is a promising non-thermal food processing technology. Researchers have made tremendous progress in the potential application of PEF in the fermented wine industry over the past few years. The objective of this paper is to systematically review the achievements of PEF technology applied to the winemaking and aging process of fermented wine. Research on the application of PEF in fermented wine suggests that PEF treatment has the following advantages: (1) shortening the maceration time of brewing materials; (2) promoting the extraction of main functional components; (3) enhancing the color of fermented wine; (4) inactivating spoilage microorganisms; and (5) accelerating the formation of aroma substances. These are mainly related to PEF-induced electroporation of biomembranes, changes in molecular structure and the occurrence of chemical reactions. In addition, the key points of PEF treatments for fermented wine are discussed and some negative impacts and research directions are proposed.

The Pulsed Electric Field Assisted-Extraction Enhanced the Yield and the Physicochemical Properties of Soluble Dietary Fiber From Orange Peel

The study aimed to investigate the effects of pulsed electric field (PEF)-assisted extraction on the yield, physicochemical properties, and structure of soluble dietary fiber (SDF) from orange peel. The results showed that the optinal parameters of PEF assisted extraction SDF was temperature of 45^oC with the electric field intensity of 6.0 kV/cm, pulses number of 30, and time of 20min and SDF treated with PEF showed the higher water solubility, water-holding and oil-holding capacity, swelling capacity, emulsifying activity, emulsion stability, foam stability and higher binding capacity for Pb²⁺, As³⁺, Cu²⁺, and higher which resulted from the higher viscosity due to PEF treatment. Compared with the untreated orange peel, the SDF obtained with PEF exhibited stronger antioxidant activities, which was due to its smaller molecular weight (189 vs. 512 kDa). In addition, scanning electron micrograph images demonstrated that the surface of PEF-SDF was rough and collapsed. Overall, it was suggested that PEF treatment could improve the physicochemical properties of SDF from the orange peel and would be the potential extraction technology with high efficiency.

Extensible and self-recoverable proteinaceous materials derived from scallop byssal thread

Biologically derived and biologically inspired fibers with outstanding mechanical properties have found attractive technical applications across diverse fields. Despite recent advances, few fibers can simultaneously possess high-extensibility and self-recovery properties especially under wet conditions. Here, we report protein-based fibers made from recombinant scallop byssal proteins with outstanding extensibility and self-recovery properties. We initially investigated the mechanical properties of the native byssal thread taken from scallop Chlamys farreri and reveal its high extensibility (327 ± 32%) that outperforms most natural biological fibers. Combining transcriptome and proteomics, we select the most abundant scallop byssal protein type 5-2 (Sbp5-2) in the thread region, and produce a recombinant protein consisting of 7 tandem repeat motifs (rTRM7) of the Sbp5-2 protein. Applying an organic solvent-enabled drawing process, we produce bio-inspired extensible rTRM7 fiber with high-extensibility (234 ± 35%) and self-recovery capability in wet condition, recapitulating the hierarchical structure and mechanical properties of the native scallop byssal thread. We further show that the mechanical properties of rTRM7 fiber are highly regulated by hydrogen bonding and intermolecular crosslinking formed through disulfide bond and metal-carboxyl coordination. With its outstanding mechanical properties, rTRM7 fiber can also be seamlessly integrated with graphene to create motion sensors and electrophysiological signal transmission electrode.

Bio-inspired materials are an intense area of study as researchers try to adapt biomaterials for other applications. Here, the authors report on the processing of protein materials derived from the byssal thread of scallops to create high-extensibility materials with self-recovery under wet conditions.

Tuning the p-Orbital Electron Structure of s-Block Metal Ca Enables a High-Performance Electrocatalyst for Oxygen Reduction

Most previous efforts are devoted to developing transition metals as electrocatalysts guided by the d-band center model. The metals of the s-block of the periodic table have so far received little attention in the application of oxygen reduction reactions (ORR). Herein, a carbon catalyst with calcium (Ca) single atom coordinated with N and O is reported, which displays exceptional ORR activities in both acidic condition (E_1/2  = 0.77 V, 0.1 m HClO₄ ) and alkaline condition (E_1/2  = 0.90 V, 0.1 m KOH). The CaN, O/C exhibits remarkable performance in zinc-air battery with a maximum power density of 218 mW cm^-2 , superior to a series of catalysts reported so far. X-ray absorption near-edge structure (XANES) characterization confirms the formation of N- and O-atom-coordinated Ca in the carbon matrix. Density functional theory (DFT) calculations reveal that the high catalytic activity of main-group Ca is ascribed to the fact that its p-orbital electron structure is regulated by N and O coordination so that the highest peak (E_P ) of the projected density of states (PDOS) for the Ca atom is moved close to the Fermi level, thereby facilitating the adsorption of ORR intermediates and electron transfer.

Non-thermal Technologies for Food Processing

Food is subjected to various thermal treatments during processes to enhance its shelf-life. But these thermal treatments may result in deterioration of the nutritional and sensory qualities of food. With the change in the lifestyle of people around the globe, their food needs have changed as well. Today's consumer demand is for clean and safe food without compromising the nutritional and sensory qualities of food. This directed the attention of food professionals toward the development of non-thermal technologies that are green, safe, and environment-friendly. In non-thermal processing, food is processed at near room temperature, so there is no damage to food because heat-sensitive nutritious materials are intact in the food, contrary to thermal processing of food. These non-thermal technologies can be utilized for treating all kinds of food like fruits, vegetables, pulses, spices, meat, fish, etc. Non-thermal technologies have emerged largely in the last few decades in food sector.

Enhanced synthesis of succinylated whey protein isolate by pulsed electric field pretreatment

The objective of this study was to investigate the feasibility of pulse electric field (PEF) as a pretreatment for whey protein isolate (WPI) before its succinylation. The degree of succinylation (DS) of WPI increased from 88.31% for native WPI to 93.45% for PEF-pretreated WPI (PWPI, initial pH 10.0) for the same succinic anhydride (SA) to WPI ratio (1:1). Fourier transform infrared spectroscopy and scanning electron microscopy analysis proved the successful succinylation of WPI. For PWPIs, the surface hydrophobicity, exposed sulphydryl, and total sulphydryl decreased, which indicates the occurrence of changes in protein structures with more hydrophilic groups and better protein dispersion. Moreover, PEF may expose more amino acid residues binding sites that are present inside the protein, which is more suitable for succinylation. Therefore, the PEF pretreatment of proteins can improve their efficient use that is expected to play a critical role in succinylation industry.

The application of PEF technology in food processing and human nutrition

During the last decades, many novel techniques of food processing have been developed in response to growing demand for safe and high quality food products. Nowadays, consumers have high expectations regarding the sensory quality, functionality and nutritional value of products. They also attach great importance to the use of environmentally-friendly technologies of food production. The aim of this review is to summarize the applications of PEF in food technology and, potentially, in production of functional food. The examples of process parameters and obtained effects for each application have been presented.

Review of the application of pulsed electric fields (PEF) technology for food processing in China

With the improvement of living standards, growing consumer demand for high-quality and natural foods has led to the development of new mild processes to enhance or replace conventional thermal and chemical methods for food processing. Pulsed electric fields (PEF) is an emerging and promising non-thermal food processing technology, which is ongoing from laboratory and pilot plant level to the industrial level. Chinese researchers have made tremendous advances in the potential applications of PEF for processing a wide range of food commodities over the last few years, which contributes to the current understanding and development of PEF technology. The objective of this paper is to conduct a systematic review on the achievements of PEF technology used for food processing in China and the corresponding processing principles. Research on the applicability of PEF in food processing suggests that PEF can be used alone or in combination with other methods, not only to inactivate microorganisms and extract active constituents, but also to modify biomacromolecules, enhance chemical reactions and accelerate the aging of fermented foods, which are mainly related to permeabilization of biomembranes, occurrence of electrochemical and electrolytic reactions, polarization and realignment of molecules, and reduction of activation energy of chemical reactions induced by PEF treatments. In addition, some of the most important challenges for the successful implementation of large-scale industrial applications of PEF technology in the food industry are discussed. The results bring out the benefits of both researchers and the industry.

Preparation of sheep bone collagen peptide-calcium chelate using enzymolysis-fermentation methodology and its structural characterization and stability analysis

In this study, enzymatic hydrolysis and Lactobacillus fermentation were used in combination to prepare collagen peptide with high free calcium content, followed by the addition of anhydrous ethanol to obtain peptide-calcium chelate. The optimal conditions for the fermentation of enzymatic hydrolysate (glucose 3%, inoculum size 6%, 24.5 h, 37 °C and pH 6.5) were determined by response surface methodology (RSM), under which a free calcium content of 2212.58 mg/100 g was obtained. The calcium-chelating capacity was 42.57 ± 0.09%. The results of ultraviolet absorption spectrum, Fourier transform infrared (FT-IR) spectra, differential scanning calorimeter (DSC), X-ray diffraction and amino acid analysis indicated that calcium could be chelated through carboxyl oxygen and amino nitrogen atoms of collagen peptides, forming peptide-calcium chelate. The chelate is stable at 30-80 °C of temperatures and during in simulated gastrointestinal digestion, which could promote calcium absorption in human. The test intended to provide a basis for developing a novel calcium supplement and promoting utilization of sheep bone.

Effect of Pulsed Electric Field Pretreatment of Date Palm Fruits on Free Amino Acids, Bioactive Components, and Physicochemical Characteristics of the Alcoholic Beverage

This research is aimed to observe the impact of pulsed electric field (PEF) application on the free amino acids, physicochemical characteristics, and bioactive components of alcoholic beverages processed from date palm fruits. The fruits were treated by PEF (frequency: 10 Hz, treatment time: 100 µs, pulses number: 40 µs for electric field: 1.38, 2.02, and 2.92 kV/cm, respectively). A significant increase (P < 0.05) in the total free amino acids and phenolic and flavonoid contents (2.92 > 2.02 > 1.38 kV/cm) was observed. There was a minor significant difference among the treated samples in the total soluble solid, alcohol, and total sugar contents, while there were no significant changes in the other parameters, including the color attributes. PRACTICAL APPLICATION: This study observed whether PEF treatment has a positive impact on the processing of alcoholic beverages of date palm fruits. PEF was found to improve the bioactive components and nutritional value of alcoholic beverages processed from date palm fruits. This finding suggests that PEF can be a better technique to enhance the quality characteristics of date palm fruit alcoholic beverages.

Quality characteristics of the processed dates vinegar under influence of ultrasound and pulsed electric field treatments

This research aimed to evaluate the influences of the pulsed electric field (PEF), ultrasound (US), and combination between them (PEF + US) on the quality of vinegar processed from date palm fruits compared with untreated vinegar (UT). Physicochemical properties, free amino acids (FAA), volatile components, organic acids, total phenolics and flavonoids, and sensory analysis were determined. The results showed that there were no significant differences in pH, total titratable acidity, ethanol content, and total sugar in all treated vinegar compared with UT. However, the values were found to be decreased (PEF + US < PEF < US < UT). Twenty-eight compounds were identified in the vinegar treated by PEF + US as the highest number of components, followed by PEF and US (23 and 22 components, respectively), compared with 19 compounds identified in UT. Compared with UT, there was a significant increase (p < 0.05) in the total FAA in dates vinegar among all treated samples (UT < US < PEF < PEF + US). Total phenolic and flavonoids contents results indicated that there was a significant increase (p < 0.05) in the treated vinegar compared with UT. Sensory analysis results indicated that no significant difference (p < 0.05) in all the parameters, except for a quite significant difference (p < 0.05) in the overall acceptability between the treated vinegar. In this study, vinegar was successfully produced from date palm fruits. Therefore, PEF + US are capable not only in enhancing the extraction process but also in the production of vinegar with good quality.

Impact of pulsed electric field treatment on drying kinetics, mass transfer, colour parameters and microstructure of plum

The aim of the present study was to scrutiny the impact of pulsed electric field (PEF) as a pre-treatment method on the convective drying kinetics, cell disintegration, colours and microstructural changes of fresh plums. In this study, the PEF intensities of 1-3 kV/cm, pulses number 30 and 70 °C drying temperature was applied to detect the drying kinetics. The specific energy consumption generated by PEF treatment was 10-90 kJ/kg. It was explored that the cell disintegration index increased from 0.147 to 0.572 with increased electric field intensity from 1 to 3 kV/cm. Further, we found that high cell disintegration leads to increase in drying rate and shorten drying time. The rates of water diffusion coefficient also increase with increasing PEF intensity from 0.27 to 16.47 × 10^-9 m²/s. PEF pre-treatment followed by convective drying results in enhanced lightness and chroma as compared to untreated plum. Furthermore, the microscopic analysis by scanning electron microscopy at 200 × revealed that the PEF treatment at 3 kV/cm had caused shrinkage in the plum tissues which might be responsible for higher diffusion rate of water in the plum. In this work was investigated that drying kinetics and mass transfer after PEF treatment to improve quality of dried plum.

Isolation and identification of calcium-chelating peptides from Pacific cod skin gelatin and their binding properties with calcium

Two novel calcium-chelating peptides have been identified from Pacific cod skin gelatin, and the binding mode of the two peptides with calcium has been elucidated.