Antioxidant activity improvement of identified pine nut peptides by pulsed electric field (PEF) and the mechanism exploration

Quality evaluation of house cricket flour processed by electrohydrodynamic drying and pulsed electric fields treatment

House crickets are expected to play a significant role in the future food sector. Electrohydrodynamic (EHD) drying offers an environmentally friendly alternative to conventional drying methods. Pulsed electric fields (PEF) is a non-thermal process that facilitates conventional processes. EHD was applied to house crickets with and without PEF pretreatment, and the effect of PEF and EHD on the quality of the insects was evaluated. PEF pretreatment positively affected the oven drying at 60 °C by reducing its duration and thus decreasing the energy consumption by 14.22%. Moisture removal of EHD was not sufficient to replace oven drying, but when combined with oven drying, the overall energy consumption was reduced by >50%. PEF processing also increased the protein solubility (53.07% higher than the respective control) and antioxidant activity (24.05% higher than the respective control) of the oven-dried samples and reduced the histamine content of the EHD-dried samples (25.87% lower than the respective control).

Plant Protein-Derived Active Peptides: A Comprehensive Review

Active peptides are a class of physiologically active protein fragments, which can be prepared from different sources. In the past few decades, the production of peptides with various effects from different plant proteins continues to receive academic attention. With advances in extraction, purification, and characterization techniques, plant protein-derived active peptides continue to be discovered. They have been proven to have various functional activities such as antioxidant, antihypertensive, immunomodulatory, antimicrobial, anti-inflammatory, antidiabetic, antithrombotic, and so on. In this review, we searched Web of Science and China National Knowledge Infrastructure for relevant articles published in recent years. There are 184 articles included in this manuscript. The current status of plant protein-derived active peptides is systematically introduced, including their sources, preparation, purification and identification methods, physiological activities, and applications in the food industry. Special emphasis has been placed on the problems of active peptide exploration and the future trend. Based on these, it is expected to provide theoretical reference for the further exploitation of plant protein-derived active peptides, and promote the healthy and rapid development of active peptide industry.

Recent and novel processing technologies coupled with enzymatic hydrolysis to enhance the production of antioxidant peptides from food proteins: A review

Antioxidant peptides obtained through enzymatic hydrolysis of food proteins exhibit a broad range of bioactivities both in vitro and in vivo models. The antioxidant peptides showed the potential to fight against the reactive oxygen species, free radicals and other pro-oxidative substances which are considered the source of various chronic diseases for humans. Both animals and plants have been recognized as natural protein sources and attracted much research interest over the synthetic ones in terms of safety. However, the main challenge remains to increase the antioxidant peptides yield, reduce the enzyme quantity and the reaction time. Consequently, different efficient and innovative food processing technologies such as thermal, ultrasound, microwave, high hydrostatic pressure, pulsed electric field, etc. have been developed and currently used to treat food proteins before (pretreatment) or during the enzymatic hydrolysis (assisted). Those technologies were found to significantly enhance the degree of hydrolysis and the production of substantial antioxidant peptides. These emerging technologies enhance the enzymatic hydrolysis by inducing protein denaturation/unfolding, and the enzymatic activation without altering their functional and nutritional properties. This review discusses the state of the art of thermal, ultrasound, high hydrostatic pressure, microwave, and pulsed electric field techniques, their applications while coupled with enzymatic hydrolysis, their comparison and potential challenges for the production of antioxidant peptides from food proteins.

Production of Food-Derived Bioactive Peptides with Potential Application in the Management of Diabetes and Obesity: A Review

The prevalence of diabetes mellitus and obesity is increasing worldwide. Bioactive peptides are naturally present in foods or in food-derived proteins. Recent research has shown that these bioactive peptides have an array of possible health benefits in the management of diabetes and obesity. First, this review will summarize the top-down and bottom-up production methods of the bioactive peptides from different protein sources. Second, the digestibility, bioavailability, and metabolic fate of the bioactive peptides are discussed. Last, the present review will discuss and explore the mechanisms by which these bioactive peptides help against obesity and diabetes based on in vitro and in vivo studies. Although several clinical studies have demonstrated that bioactive peptides are beneficial in alleviating diabetes and obesity, more double-blind randomized controlled trials are needed in the future. This review has provided novel insights into the potential of food-derived bioactive peptides as functional foods or nutraceuticals to manage obesity and diabetes.

Impact of Non-Thermal Technologies on the Quality of Nuts: A Review

Nuts are widely consumed worldwide, mainly due to their characteristic flavor and texture, ease of consumption, and their functional properties. In addition, consumers increasingly demand natural or slightly processed foods with high quality. Consequently, non-thermal treatments are a viable alternative to thermal treatments used to guarantee safety and long shelf life, which produce undesirable changes that affect the sensory quality of nuts. Non-thermal treatments can achieve results similar to those of the traditional (thermal) ones in terms of food safety, while ensuring minimal loss of bioactive compounds and sensory properties, thus obtaining a product as similar as possible to the fresh one. This article focuses on a review of the main non-thermal treatments currently available for nuts (cold plasma, high pressure, irradiation, pulsed electric field, pulsed light, ultrasound and ultraviolet light) in relation to their effects on the quality and safety of nuts. All the treatments studied have shown promise with regard to the inhibition of the main microorganisms affecting nuts (e.g., Aspergillus, Salmonella, and E. coli). Furthermore, by optimizing the treatment, it is possible to maintain the organoleptic and functional properties of these products.

Enhancing the Biological Activities of Food Protein-Derived Peptides Using Non-Thermal Technologies: A Review

Bioactive peptides (BPs) derived from animal and plant proteins are important food functional ingredients with many promising health-promoting properties. In the food industry, enzymatic hydrolysis is the most common technique employed for the liberation of BPs from proteins in which conventional heat treatment is used as pre-treatment to enhance hydrolytic action. In recent years, application of non-thermal food processing technologies such as ultrasound (US), high-pressure processing (HPP), and pulsed electric field (PEF) as pre-treatment methods has gained considerable research attention owing to the enhancement in yield and bioactivity of resulting peptides. This review provides an overview of bioactivities of peptides obtained from animal and plant proteins and an insight into the impact of US, HPP, and PEF as non-thermal treatment prior to enzymolysis on the generation of food-derived BPs and resulting bioactivities. US, HPP, and PEF were reported to improve antioxidant, angiotensin-converting enzyme (ACE)-inhibitory, antimicrobial, and antidiabetic properties of the food-derived BPs. The primary modes of action are due to conformational changes of food proteins caused by US, HPP, and PEF, improving the susceptibility of proteins to protease cleavage and subsequent proteolysis. However, the use of other non-thermal techniques such as cold plasma, radiofrequency electric field, dense phase carbon dioxide, and oscillating magnetic fields has not been examined in the generation of BPs from food proteins.

Production, Purification, and Potential Health Applications of Edible Seeds' Bioactive Peptides: A Concise Review

Edible seeds play a significant role in contributing essential nutritional needs and impart several health benefits to improve the quality of human life. Previous literature evidence has confirmed that edible seed proteins, their enzymatic hydrolysates, and bioactive peptides (BAPs) have proven and potential attributes to ameliorate numerous chronic disorders through the modulation of activities of several molecular markers. Edible seed-derived proteins and peptides have gained much interest from researchers worldwide as ingredients to formulate therapeutic functional foods and nutraceuticals. In this review, four main methods are discussed (enzymatic hydrolysis, gastrointestinal digestion, fermentation, and genetic engineering) that are used for the production of BAPs, including their purification and characterization. This article’s main aim is to provide current knowledge regarding several health-promoting properties of edible seed BAPs in terms of antihypertensive, anti-cancer, antioxidative, anti-inflammatory, and hypoglycemic activities.

Effect of Supercritical Extract from Black Poplar and Basket Willow on the Quality of Natural and Probiotic Drinkable Yogurt

Yogurt is a fermented milk drink produced by Streptococcus thermophilus, Lactobacillus delbrüeckii ssp. bulgaricus, or Lactobacillus rhamnosus, which can be enriched with polyphenolic compounds to enhance its antioxidant properties. Supercritical (scCO2/H2O) extracts obtained from the mixture of bark and wood of black poplar (Populus nigra) and basket willow (Salix viminalis) are the source of bioactive compounds. The aim of the study was to assess the effect of supercritical extracts from the P. nigra and S. viminalis on the fermentation, quality, and bioactive properties of drinkable natural and probiotic yogurts. The incorporation of scCO2/H2O extracts at a dose of 0.01% (w/v) into milk for the production of natural and probiotic yogurts increases their functional properties by enhancing the antioxidant activity without causing negative effects on the physicochemical and organoleptic properties of products. The antioxidant activity of yogurt with scCO2/H2O extract from P. nigra and S. viminalis was higher than control yogurts by 1.3-13.2% and 4.4-37.5%, respectively. The addition of a supercritical S. viminalis extract reduced the time of natural and probiotic yogurt fermentation. Natural and probiotic yogurt with scCO2/H2O extracts added was characterised by a bacterial population size of over 7 log cfu/g, and the microflora was active throughout the cold storage period. FTIR analysis confirmed the presence of scCO2/H2O extracts from P. nigra or S. viminalis in both types of yogurt. A secondary structure analysis confirmed interactions between compounds of scCO2/H2O extract from P. nigra and S. viminalis extract with milk proteins. These interactions affect the compounds' structural and functional properties by changing, e.g., their digestibility and antioxidant properties.

Study on the domain selective inhibition of angiotensin-converting enzyme (ACE) by food-derived tyrosine-containing dipeptides

In this article, the selective inhibition of several tyrosine-containing dipeptides on N and C domain of ACE (angiotensin-converting enzyme) was studied, and the interaction mode of ACE and inhibitors was simulated by molecular docking. MTT assay was used to detect the effect of dipeptide on human umbilical vein endothelial cells (HUVEC). The results showed that the food-derived dipeptides AY (Ala-Tyr), LY (Leu-Tyr), and IY (Ile-Tyr) containing tyrosine at the C-terminal were favorable structures for selective inhibition of ACE C-domain. These dipeptides showed competitive and mixed inhibition patterns, while the dipeptides EY (Glu-Tyr), RY (Arg-Tyr), FY (Phe-Tyr), and SY (Ser-Tyr) showed noncompetitive inhibition. Food-derived dipeptides containing tyrosine have no cytotoxicity on HUVEC cells, which provides a basis for the application of food-derived tyrosine dipeptides as antihypertensive peptides. This study provides a theoretical basis for exploring the selective inhibition mechanism of ACE inhibitory peptides containing tyrosine residue. PRACTICAL APPLICATIONS: Angiotensin-converting enzyme (ACE) is a two-domain dipeptidyl carboxypeptidase, which is a key enzyme to regulate blood pressure. ACE has two active sites, C- and N-domain, which have high catalytic activity. Although the amino acid sequences of the two active sites have 60% similarity, there are some differences in structure and function. The action mechanism of ACE domain should be clarified, and the structure-activity relationship between inhibitors and ACE domain has not been systematically studied. The aim of this study was to identify the selective inhibitory effect of food-derived tyrosine dipeptides on the domain of ACE. This provides a new idea for finding new antihypertensive drugs with less side effects.

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.

Electric field effects on proteins - Novel perspectives on food and potential health implications

Electric fields (EF) technologies have been establishing a solid position in emergent food processing and have seen as serious alternatives to traditional thermal processing. During the last decades, research has been devoted to elucidation of technological and safety issues but also fundamental aspects related with interaction of electric fields (EF) with important macromolecules, such as proteins. Proteins are building blocks for the development of functional networks that can encompass health benefits (i.e. nutritional and bioactive properties) but may be also linked with adverse effects such as neurodegenerative diseases (amyloid fibrils) and immunological responses. The biological function of a protein depends on its tridimensional structure/conformation, and latest research evidences that EF can promote disturbances on protein conformation, change their unfolding mechanisms, aggregation and interaction patterns. This review aims at bringing together these recent findings as well as providing novel perspectives about how EF can shape the behavior of proteins towards the development of innovative foods, aiming at consumers' health and wellbeing.

Production and processing of antioxidant bioactive peptides: A driving force for the functional food market

Recently, the demand for functional foods in the global market has increased rapidly due to the increasing occurrences of non-communicable diseases and technological advancement. Antioxidant peptides have been suggested as ingredients used to produce health-promoting foods. These peptides are encrypted from various food derived protein sources by chemical and enzymatic hydrolysis, and microbial fermentation. However, the industrial-scale production of antioxidant peptides is hampered by different problems such as high production cost, and low yield and bioactivity. Accordingly, novel processing technologies, such as high pressure, microwave and pulsed electric field, have been recently emerged to overcome the problems associated with the conventional hydrolysis methods. This particular review, therefore, discussed the current processing technologies used to produce antioxidant peptides. The review also suggested further perspectives that should be addressed in the future.

Advances on Food-Derived Peptidic Antioxidants-A Review

The oxidation process is considered to be the main reason behind human aging, human degenerative diseases and food quality degradation. Food-derived peptidic antioxidants (PAs) have wide sources and great activity, and have broad application prospects in removing excess reactive oxygen species in the body, anti-aging and preventing and treating diseases related to oxidative stress. On the other hand, PAs are expected to inhibit the lipid peroxidation of foods and increase the stability of the food system in the food industry. However, the production pathways and action mechanism of food-derived PAs are diverse, which makes it is difficult to evaluate the performance of PAs which is why the commercial application of PAs is still in its infancy. This article focuses on reviewing the preparation, purification, and characterization methods of food-derived PAs, and expounds the latest progress in performance evaluation and potential applications, in order to provide an effective reference for subsequent related research of PAs.

High-Pressure Carbon Dioxide Used for Pasteurization in Food Industry

The demand for safe, high-quality food has greatly increased, in recent times. As traditional thermal pasteurization can significantly impact the nutritional value and the color of fresh food, an increasing number of nonthermal pasteurization technologies have attracted attention. The bactericidal effect of high-pressure carbon dioxide has been known for many years, and its effect on food-related enzymes has been studied. This novel technology has many merits, owing to its use of relatively low pressures and temperatures, which make it a potentially valuable future method for nonthermal pasteurization. For example, the inactivation of polyphenol oxidase can be achieved with relatively low temperature and pressure, and this can contribute to food quality and better preserve nutrients, such as vitamin C. However, this novel technology has yet to be developed on an industrial scale due to insufficient test data. In order to support the further development of this application, on an industrial scale, we have reviewed the existing information on high-pressure carbon dioxide pasteurization technology. We include its bactericidal effects and its influence on food quality. We also pave the way for future studies, by highlighting key areas.

Use of a combination of the MD simulations and NMR spectroscopy to determine the regulatory mechanism of pulsed electric field (PEF) targeting at C-terminal histidine of VNAVLH

In this study, the targeted regulatory mechanism of pulsed electric field (PEF) was explored for antioxidant activity improvement in four peptides, RGAVIH, RGAVLH, VNAVIH, and VNAVLH, of the pine nut (Pinus koraiensis Sieb. et Zucc). The VNAVLH peptide exhibited the best antioxidant activity and the β-sheet content decreased to a minimum value at 40 kV/cm. Moreover, the chemical shifts of hydrogen atoms of 2-H Asn and 6-H His shifted to a higher magnetic field. The connectivity between N_αH (3.62 ppm) and C_αH (8.10 ppm) of 6-His residue disappeared in PEF-treated peptide. Molecule dynamics (MD) simulation verified that the distances of N_α(H₇₈)-C_α(H₈₀) and H₈₂-O₉₄ increased, whereas -OH and -C_β(H₈₃) got closer in histidine residue after applying the electric field force. Therefore, the antioxidant activity enhancement of VNAVLH might due to the targeted regulation of PEF treatment on N_αH-C_αH and imidazole group in histidine.

Green and Sustainable Valorization of Bioactive Phenolic Compounds from Pinus By-Products

In Europe, pine forests are one of the most extended forests formations, making pine residues and by-products an important source of compounds with high industrial interest as well as for bioenergy production. Moreover, the valorization of lumber industry residues is desirable from a circular economy perspective. Different extraction methods and solvents have been used, resulting in extracts with different constituents and consequently with different bioactivities. Recently, emerging and green technologies as ultrasounds, microwaves, supercritical fluids, pressurized liquids, and electric fields have appeared as promising tools for bioactive compounds extraction in alignment with the Green Chemistry principles. Pine extracts have attracted the researchers’ attention because of the positive bioproperties, such as anti-inflammatory, antimicrobial, anti-neurodegenerative, antitumoral, cardioprotective, etc., and potential industrial applications as functional foods, food additives as preservatives, nutraceuticals, pharmaceuticals, and cosmetics. Phenolic compounds are responsible for many of these bioactivities. However, there is not much information in the literature about the individual phenolic compounds of extracts from the pine species. The present review is about the reutilization of residues and by-products from the pine species, using ecofriendly technologies to obtain added-value bioactive compounds for industrial applications.

Effects of induced electric field (IEF) on the reduction of Saccharomyces cerevisiae and quality of fresh apple juice

The non-conventional technologies about continuous sterilization of liquid food were focused on recently, which is benefits for industrialization. In this study, the machine with an induced electric field was used to sterilize S. cerevisiae in apple juice and the juice quality also was researched. The optimal condition is 800 V, 400 Hz, 5 rpm and 2 mm. Furthermore, the sterilization of the IEF was attributed to non-thermal and thermal effects. The IEF treatment group has a reduction of about 4.6 logs (CFU/mL) in S. cerevisiae at 400 Hz, 800 V, and 2 mm, while the non-thermal group is nearly 2 logs (CFU/mL). The improvement of conductivity and the reduction of pH value imply that IEF might destroy the cell structure. Meanwhile, polyphenol compounds and amino acids in the IEF group were protected well than other groups. Generally, IEF is a potential technology for industrial sterilization of liquid beverages.

Tryptophan targeted pulsed electric field treatment for enhanced immune activity in pine nut peptides

To investigate immune activity of pine nut peptides treated by PEF technology and mechanism of targeting immunoactive sitesits, immune regulatory active was evaluated by RAW 264.7 cells model and the structures of pine nut peptides were researched by fluorescence, CD, and 1D/2D NMR spectrum. These consequences showed the ability of macrophages to phagocytosis neutral red and the production of nitric oxide (NO) were improved after PEF treatment. KWFCT treated by PEF treatment with 40 kV/cm obtained the best immunocompetence. The CD spectroscopy showed that PEF could transform the secondary structures of pine nut peptides. The short-range correlation between C_γ H (1.65 ppm) and C_α H (3.35 ppm), and long-range correlation between C_α H (3.37 ppm) and N_α H (8.07 ppm) were enhanced by PEF treatment. PEF treatment of tryptophan in the pine nut peptides enhanced the immunological activity of the pine nut peptides. PRACTICAL APPLICATIONS: Bioactive peptides derived from food proteins have been extensively studied in recent years. However, little research has been done on the immunoactive peptide of pine nut source. PEF treatment is promising for improving certain properties of foods while maintaining the flavor, color, taste, and nutritional value of the food. This research demonstrated that PEF treatment increased the immunological activity of KWFCT and KWFM. The primary structure of KWFCT and KWFM did not change after PEF treatment, but the secondary structure was transformed into each other. A new perspective on the PEF action site is proposed, which is beneficial to the application of PEF technology.

A biotechnological approach for the production of branched chain amino acid containing bioactive peptides to improve human health: A review

Improper nutrition provokes many types of chronic diseases and health problems, which consequently are associated with particularly high costs of treatments. Nowadays, consumer's interest in healthy eating is shifting towards specific foods or food ingredients. As a consequence, bioactive peptides as a promising source of health promoting food additives are currently an intensely debated topic in research. Process design is still on its early stages and is significantly influenced by important preliminary decisions. Thus, parameters like peptide bioactivity within the product, selection of the protein source, enzyme selection for hydrolysis, peptide enrichment method, as well as stability of the peptides within the food matrix and bioavailability are sensitive decision points, which have to be purposefully coordinated, as they are directly linked to amino acid content and structure properties of the peptides. Branched chain amino acids (BCAA) are essential components for humans, possessing various important physiologic functions within the body. Incorporated within peptide sequences, they may induce dual functions, when used as nutraceuticals in functional food, thus preserving the foodstuff and prevent several widespread diseases. Furthermore, there is evidence that consuming this peptide-class can be a nutritional support for elderly people or improve human health to prevent diseases caused by incorrect nutrition. Based on the knowledge about the role of BCAA within various peptide functions, discussed in the review, special attention is given to different approaches for systematic selection of the protein source and enzymes used in hydrolysis, as well as suitable peptide enrichment methods, thereby showing current trends in research.

Immunomodulatory Activity Improvement of Pine Nut Peptides by a Pulsed Electric Field and Their Structure-Activity Relationships

In this study, Alg-Gly-Ala-Val-Leu-His (RGAVLH) obtained from pine nut ( Pinus koraiensis Sieb. et Zucc.) protein was chosen to investigate the phenomenon of immunomodulatory activity improvement upon pulsed electric field (PEF) processing. The influence of electric field intensity on immunomodulatory activity of RGAVLH was evaluated using RAW 264.7 cells. It was found that RGAVLH can not only significantly ( p < 0.05) improve the capability of macrophage phagocytosis but also promote the production of nitric oxide. RGAVLH treated under an electric field intensity of 40 kV/cm exhibited the best immunomodulatory activity. The primary and secondary structures of PEF-treated peptides were analyzed by mid-infrared (MIR) spectroscopy, Raman spectroscopy, circular dichroism spectroscopy, and one-dimensional/two-dimensional nuclear magnetic resonance spectroscopy. After PEF treatment, the primary structure of RGAVLH was not influenced, as evaluated by MIR and Raman spectra. In addition, the content of β-sheet was decreased and active hydrogen was changed in PEF-treated RGAVLH solution. Moreover, the long-range connectivity between C_αH (3.39 ppm) and N_αH (8.24 ppm) was enhanced by PEF. Therefore, the improvement of the immunomodulatory activity of RGAVLH might result from the changes of the spatial state and spatial force in the peptide solution system.

Intracellular antioxidant activity and apoptosis inhibition capacity of PEF-treated KDHCH in HepG2 cells

The effect of pulsed electric field (PEF) treatment on the intracellular antioxidant and apoptotic activity of the peptide Lys-Asp-His-Cys-His (KDHCH) was examined using model HepG2 cells. First, PEF treatment conditions specific for the antioxidant peptide were optimized, and it was found that PEF treatment could enhance DPPH, ABTS and hydroxyl radical scavenging capacity of KDHCH. Second, KDHCH subjected to PEF treatment at 1800 Hz and 15 kV/cm was investigated using various intracellular antioxidant assays. PEF treatment decreased the EC50 value and increased the protective ability of oxidative stress inhibition and reactive oxygen species (ROS) scavenging activity of KDHCH. Furthermore, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH-PX) and glutathione reductase (GR) activities of KDHCH-pre-treated HepG2 cells increased significantly compared with those of the H₂O₂ damaged group, whereas lactate dehydrogenase (LDH) and malonaldehyde (MDA) content were decreased. PEF-treated KDHCH exhibited an increased capacity to maintain the stability of mitochondrial membrane potential (MMP) and reduced the level of caspase-3. These results indicate that PEF treatment can enhance the intracellular antioxidant activity of KDHCH, which can inhibit the effect of H₂O₂ oxidation on HepG2 cells by inhibiting the accumulation of intracellular ROS, regulating antioxidant related enzymes, and blocking the apoptotic mitochondrial pathways activated by ROS.

The purification, identification and bioactivity study of a novel calcium-binding peptide from casein hydrolysate

In this study, a novel calcium-binding peptide from casein hydrolysate was purified using reversed-phase high performance liquid chromatography and sequenced by high-performance liquid chromatography-mass spectrometry (MS)/MS.

A possible mechanism for enhancing the antioxidant activity by pulsed electric field on pine nut peptide Glutamine-Tryptophan-Phenylalanine-Histidine

The aim of this study was to investigate the possible mechanism for increasing the antioxidant activity on peptide Glutamine-Tryptophan-Phenylalanine-Histidine (QWFH) from pine nut (Pinus koraiensis) protein by a pulsed electric field (PEF). The antioxidant capacity of PEF-treated QWFH increased significantly (p < 0.05) through 1,1-diphenyl-2-pycryl-hydrazyl radical scavenging and oxygen radical absorbance capacity assays. A series of mechanism exploration methods, including reversed-phase high-performance liquid chromatography, ultraviolet absorption spectroscopy, intrinsic fluorescence spectra, circular dichroism spectroscopy, and 1D and 2D nuclear magnetic resonance spectroscopies, were applied. QWFH chain was not cleaved by the PEF treatment, while more aromatic amino acids (Trp and Phe) were exposed to the polar solvent. In addition, the content of random coil of QWFH in solution was increased and its active hydrogen was changed after the PEF treatment. Moreover, the long-range connectivity between OH (14.234 ppm) on 4-H His, N_α H (7.295 ppm) on 3-H Phe, and N_α H₂ (6.801 ppm) on 1-H Gln disappeared due to the PEF. PRACTICAL APPLICATIONS: Antioxidants have been extensively explored as a potential drug to decrease the risk of certain chronic diseases. Food-derived bioactive compounds are safer than synthetic antioxidants for human health and well-being. And the PEF technology is one of the promising processes for improving the biological activity of food components. Currently, the activity of the antioxidant peptide QWFH increased after a PEF treatment. The basic structure of QWFH did not change, but the unfolding of the secondary structure on the peptide chain and the displacement of the active hydrogen increased the antioxidant activity of the peptide. Thus, the range of application of a PEF has been expanded and it also benefited the development of more functional factors in the functional food industry.

Exploration of the molecular interactions between angiotensin-I-converting enzyme (ACE) and the inhibitory peptides derived from hazelnut (Corylus heterophylla Fisch.)

The mechanism of action of food-derived angiotensin-I-converting enzyme (ACE) inhibitory peptides has not been completely elucidated. In the present study, ion-exchange chromatography, gel filtration chromatography, reverse phase-high performance liquid chromatography, and liquid chromatography-electrospray ionization-tandem mass (LC-ESI-MS/MS) were employed for purifying and identifying the ACE inhibitory peptides from hazelnut. To understand the mode of action of these peptides, ACE inhibition kinetics, in vitro and in vivo bioavailability assays, active site analysis, and interaction between the inhibitory peptides and ACE were investigated. The results identified novel ACE inhibitory peptides Ala-Val-Lys-Val-Leu (AVKVL), Tyr-Leu-Val-Arg (YLVR), and Thr-Leu-Val-Gly-Arg (TLVGR) with IC₅₀ values of 73.06, 15.42, and 249.3 μM, respectively. All peptides inhibited the ACE activity via a non-competitive mode. The binding free energies of AVKVL, YLVR, and TLVGR for ACE were -3.46, -6.48, and -7.37 kcal/mol, respectively. The strong inhibition of ACE by YLVR may be attributed to the formation of cation-pi interactions.

Effects of pulsed electric field on intracellular antioxidant activity and antioxidant enzyme regulating capacities of pine nut (Pinus koraiensis) peptide QDHCH in HepG2 cells

Effects of pulse electric field (PEF) on antioxidant activity of pine nut (Pinus koraiensis) peptide were discussed using H₂O₂-induced HepG2 cells and changes of peptide structures were measured by MIR, NMR and CD spectra. Using HPLC-MS/MS, a novel peptide was identified as QDHCH. After PEF treatment the DPPH and ABTS radical inhibition, and CAA values of QDHCH were increased to 85.13%±0.17%, 95.45%±0.12%, and 4670.10μmol of quercetin equivalents/100g. The PEF-treated QDHCH has better protective oxidative stress inhibitory of 74.22±3.70%, and the T-SOD, CAT, GSH-Px and GSH-Rx activities in cells were significantly increased by 91.92, 7.98, 18.5 and 18.79U/mg prot, while the MDA content was decreased to 8.45±0.71U/mg prot compared with H₂O₂ damaged group. In addition, the hydroxyl radical scavenging activity of QDHCH was increased by 10.53%; the basic structure was not changed by PEF, while the influenced secondary structures may induce the antioxidant activity improvement in HepG2 cells.

Bioactive Peptides

The increased consumer awareness of the health promoting effects of functional foods and nutraceuticals is the driving force of the functional food and nutraceutical market. Bioactive peptides are known for their high tissue affinity, specificity and efficiency in promoting health. For this reason, the search for food-derived bioactive peptides has increased exponentially. Over the years, many potential bioactive peptides from food have been documented; yet, obstacles such as the need to establish optimal conditions for industrial scale production and the absence of well-designed clinical trials to provide robust evidence for proving health claims continue to exist. Other important factors such as the possibility of allergenicity, cytotoxicity and the stability of the peptides during gastrointestinal digestion would need to be addressed. This review discusses our current knowledge on the health effects of food-derived bioactive peptides, their processing methods and challenges in their development.

Formation of crystalline nanoparticles by iron binding to pentapeptide (Asp-His-Thr-Lys-Glu) from egg white hydrolysates

A novel peptide (DHTKE) from egg white hydrolysates could bind iron ions in a 1 : 2 ratioviaits amide and carboxyl groups, forming the DHTKE-iron complex which belongs to crystalline nanoparticles.