Effects of rice protein hydrolysates prepared by microbial proteases and ultrafiltration on free radicals and meat lipid oxidation

Non-animal protein hydrolysates from agro-industrial wastes: A prospect of alternative inputs for cultured meat

In light of the growing demand for alternative protein sources, laboratory-grown meat has been proposed as a potential solution to the challenges posed by conventional meat production. Cultured meat does not require animal slaughter and uses sustainable production methods, contributing to animal welfare, human health, and environmental sustainability. However, some challenges still need to be addressed in cultured meat production, such as the use of fetal bovine serum for medium supplementation. This ingredient has limited availability, increases production costs, and raises ethical concerns. This review explores the potential of non-animal protein hydrolysates derived from agro-industrial wastes as substitutes for critical components of fetal bovine serum in cultured meat production. Despite the lack of standardization of hydrolysate composition, the potential benefits of this alternative protein source may outweigh its disadvantages. Future research holds promise for increasing the accessibility of cultured meat.

Protein hydrolysates of Moringa oleifera seed: Antioxidant and antihyperglycaemic potential as ingredient for the management of type-2 diabetes

New plant proteins with high nutritional quality and biological properties are actively searched worldwide. Moringa oleifera seed protein isolate was prepared from defatted flour and hydrolyzed using four proteases namely trypsin, pepsin, Alcalase, and thermolysin. Then, antioxidant activity and cellular glucose uptake properties of the hydrolysates were assessed. A high degree of hydrolysis was obtained for hydrolysate prepared using trypsin (60.07%), followed by pepsin (57.14%), Alcalase (50.68%), and thermolysin (45.45%). Thermolysin hydrolysate was the most antioxidant efficient (IC50 0.15 and 0.74 mg/mL for 2,2'-azino-bis(acide 3-ethylbenzothiazoline-6-sulfonique) diammonium salt (ABTS) and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging activity, respectively). Trypsin hydrolysate stimulated high glucose uptake by yeast cells (12.34-35.28%). In the absence of insulin, Alcalase hydrolysate was the most efficient for glucose uptake by the muscle, with the rate ranging from 22.03% to 29.93% after 30 min, then from 29.55% to 34.6% after 60 min. The four hydrolysates improved glucose uptake by the muscle in the presence of insulin with the rate ranging from 46.88% to 58.03% after 30 min, and from 50% to 58.18% after 60 min. Therefore, Moringa oleifera seed proteins could be used to prepare peptides as components of functional foods for the management of type-2 diabetes.

Modification and Solubility Enhancement of Rice Protein and Its Application in Food Processing: A Review

Rice protein is a high-quality plant-based protein source that is gluten-free, with high biological value and low allergenicity. However, the low solubility of rice protein not only affects its functional properties such as emulsification, gelling, and water-holding capacity but also greatly limits its applications in the food industry. Therefore, it is crucial to modify and improve the solubility of rice protein. In summary, this article discusses the underlying causes of the low solubility of rice protein, including the presence of high contents of hydrophobic amino acid residues, disulfide bonds, and intermolecular hydrogen bonds. Additionally, it covers the shortcomings of traditional modification methods and the latest compound improvement methods, compares various modification methods, and puts forward the best sustainable, economical, and environmentally friendly method. Finally, this article lists the uses of modified rice protein in dairy, meat, and baked goods, providing a reference for the extensive application of rice protein in the food industry.

Dynamic alterations in protein, sensory, chemical, and oxidative properties occurring in meat during thermal and non-thermal processing techniques: A comprehensive review

Meat processing represents an inevitable part of meat and meat products preparation for human consumption. Both thermal and non-thermal processing techniques, both commercial and domestic, are able to induce chemical and muscle's proteins modification which can have implication on oxidative and sensory meat characteristics. Consumers' necessity for minimally processed foods has paved a successful way to unprecedented exploration into various novel non-thermal food processing techniques. Processing of meat can have serious implications on its nutritional profile and digestibility of meat proteins in the digestive system. A plethora of food processing techniques can potentially induce alterations in the protein structure, palatability, bioavailability and digestibility via various phenomena predominantly denaturation and Maillard reaction. Apart from these, sensory attributes such as color, crispness, hardness, and total acceptance get adversely affected during various thermal treatments in meat. A major incentive in the adoption of non-thermal food processing is its energy efficiency. Considering this, several non-thermal processing techniques have been developed for evading the effects of conventional thermal treatments on food materials with respect to Maillard reactions, color changes, and off-flavor development. Few significant non-thermal processing techniques, such as microwave heating, comminution, and enzyme addition can positively affect protein digestibility as well as enhance the value of the final product. Furthermore, ultrasound, irradiation, high-pressure processing, and pulsed electric fields are other pivotal non-thermal food processing technologies in meat and meat-related products. The present review examines how different thermal and non-thermal processing techniques, such as sous-vide, microwave, stewing, roasting, boiling, frying, grilling, and steam cooking, affect meat proteins, chemical composition, oxidation, and sensory profile.

Synergistic inhibition of Pseudomonas fluorescens growth and proteases activities via sodium chlorite-based oxyhalogen

Pseudomonas fluorescens is considered among the main spoilage microorganisms due to its ability to produce proteases. Food deterioration caused by spoilage microorganisms has a major impact on food quality and the environment. The inactivation of Pseudomonas fluorescens growth and protease production was intensively investigated with the use of Salmide®, A Sodium Chlorite-Based Oxy-halogen Disinfectant. A unique M9 media was also developed to assure sufficient protease productions with different mutants of Pseudomonas fluorescens as a microbioreactor. Mutations were induced by classical whole-cell mutagenesis using N-methyl-N'- nitro-N-nitrosoguanidine (NTG). A dramatic decrease occurred in protease activity when different Salmide concentrations (5, 10, and 15 ppm) were added to the growth culture followed by a complete inhibition concentration (20, 25, 50, and 100 ppm) of Salmide. However, no significant inhibition occurred once it is secreted out of cells. Some mutants were resistant and remains highly stable with high protease production under stressful conditions of Sodium Chlorite-Based Oxy-halogen. The production of the protease showed a linear correlation with the increase in incubation time using a continuous culture bioreactor system and recorded maximum protease activity after 40 h. Our findings would offer alternative antimicrobial procedures for food and industrial sectors.

Recent application of protein hydrolysates in food texture modification

The demand for clean labels has increased the importance of natural texture modifying ingredients. Proteins are unique compounds that can impart unique textural and structural changes in food. However, lack of solubility and extensive aggregability of proteins have increased the demand for enzymatically hydrolyzed proteins, to impart functional and structural modifications to food products. The review elaborates the recent application of various proteins, protein hydrolysates, and their role in texture modification. The impact of protein hydrolysates interaction with other food macromolecules, the effect of pretreatments, and dependence of various protein functionalities on textural and structural modification of food products with controlled enzymatic hydrolysis are explained in detail. Many researchers have acknowledged the positive effect of enzymatically hydrolyzed proteins on texture modification over natural protein. With enzymatic hydrolysis, various textural properties including foaming, gelling, emulsifying, water holding capacity have been effectively improved. It is evident that each protein is unique and imparts exceptional structural changes to different food products. Thus, selection of protein requires a fundamental understanding of its structure-substrate property relation. For wider applicability in the industrial sector, more studies on interactions at the molecular level, dosage, functionality changes, and sensorial attributes of protein hydrolysates in food systems are required.

Altering functional properties of rice protein hydrolysates by covalent conjugation with chlorogenic acid

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Rice protein hydrolysate was covalently conjugated to chlorogenic acid by three methods.

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Covalent conjugation resulted in an unfolded structure of rice protein hydrolysate.

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LYS might be the binding sites for chlorogenic acid grafted on rice protein hydrolysate.

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Conjugates formed by alkaline method exhibited highest functional property.

Proteins and phenolic compounds are common components in foods that readily interact with each other to yield complexes, leading to changes in the functional properties. In this study, we investigated the effect of covalent conjugation of rice protein hydrolysates (RPH) with chlorogenic acid (CA) on the structural and functional properties of RPH. Three RPH-CA conjugates were prepared by the alkaline, enzyme, and free radical methods, respectively. Covalent conjugation decreased the content of free amino, thiol, and tyrosine groups, and increased in the amount of CA bounds from 15.23 to 21.11 nmol/mg. Moreover, the circular dichroism analysis revealed that covalent conjugation resulted in an increase of random coils. The emulsifying activity and antioxidant capacity of RPH were also improved by the covalent conjugation with CA. This work provides a better understanding of the formation of hydrolysates-chlorogenic acid conjugates, contributing to improving the functional properties of foods.

Enzymatic Hydrolysis of Broken Rice Protein: Antioxidant Activities by Chemical and Cellular Antioxidant Methods

Excessive reactive oxygen species (ROS) is an important cause of aging, and supplementing antioxidants through diet is one of the important ways to delay aging. Some studies have confirmed that rice protease hydrolysate has antioxidant activity, but was rarely been investigated on cells. Thus, commercial enzymes, alkaline enzyme, neutral enzyme, pepsin, chymotrypsin, and trypsin were selected to hydrolyze broken rice protein (BRP) to obtain the corresponding hydrolysates, which were A-broken rice protein hydrolysate (BRPH), N-BRPH, P-BRPH, C-BRPH, and T-BRPH, respectively. Then the antioxidant properties of BRPHs were evaluated by different chemical and cellular antioxidation. Molecular weight, peptide length distribution, and amino acid sequence were detected to insight into the antioxidant properties. Among BRPHs, the A-BRPH displayed the strongest hydroxyl radical scavenging activity (IC50 = 1.159 mg/ml) and metal ion-chelating activities (IC50 = 0.391 mg/ml). Furthermore, cellular antioxidation confirmed that A-BRPH significantly increased cell viability and inhibited the intracellular ROS release in both aging cells and cell-aging processes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results revealed that peptides with molecular weight <14.5 KDa were produced by enzymatic hydrolysis. Additionally, A-BRPH rich in low molecular weight (<3 kDa) and short-length peptides with some specific amino acids, such as aromatic and hydrophobic amino acids, contributes to the antioxidant properties. This study provided theoretical to the utilization of broken rice and confirmed that A-BRPH could be used in new anti-aging food and health products for human consumption.

Effects of temperature and pH on the structure of a metalloprotease from Lactobacillus fermentum R6 isolated from Harbin dry sausages and molecular docking between protease and meat protein

BACKGROUND

Microbial protease can interact with meat protein in fermented meat products at a certain pH and temperature. To investigate the effects of various pH values and temperatures on the structural characteristics of Lactobacillus fermentum R6 protease, which was isolated from Harbin dry sausages, spectroscopy techniques and molecular dynamics were utilized to evaluate structural changes.

RESULTS

The protease exhibited a stable spatial structure at pH 7 and 40 °C, and the extension of the protease structure was also promoted. Although the structure of the protease could be changed or destroyed by pH 8 and 70 °C, it was mainly determined by the changes of secondary and tertiary structures such as α-helix, β-sheet, β-turn and random coil. In addition, carbonyl vibration, -NH vibration, C-H stretching vibration and disulphide bonds were present in L. fermentum R6 protease under various pH and temperature conditions. Molecular docking showed that the protease can interact with myosin light chain, myosin heavy chain, actin and myoglobin.

CONCLUSION

The protease can maintain stable structure and interact with meat protein, which reflected certain application prospects in the fermentation of Harbin dry sausages. © 2021 Society of Chemical Industry.

Evaluating the Antioxidants, Whitening and Antiaging Properties of Rice Protein Hydrolysates

Plant-derived protein hydrolysates have potential applications in nutrition. Rice protein hydrolysates (RPHs), an excellent source of proteins, have attracted attention for the development of cosmeceuticals. However, few studies have reported the potential application of RPH in analysis, and this study examined their antioxidant activities and the inhibitory activities of skin aging enzymes. The results indicated that the total phenolic and flavonoid concentrations were 2.06 ± 0.13 mg gallic acid equivalent/g RPHs and 25.96 ± 0.52 µg quercetin equivalent/g RPHs, respectively. RPHs demonstrated dose-dependent activity for scavenging free radicals from 1,1-diphenyl-2-picrylhydrazyl [half-maximal inhibitory concentration (IC50) = 42.58 ± 2.1 mg/g RPHs] and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (IC50 = 2.11 ± 0.88 mg/g RPHs), dose-dependent reduction capacity (6.95 ± 1.40 mg vitamin C equivalent/g RPHs) and oxygen radical absorbance capacity (473 µmol Trolox equivalent/g RPHs). The concentrations of the RPH solution required to achieve 50% inhibition of hyaluronidase and tyrosinase activities were determined to be 8.91 and 107.6 mg/mL, respectively. This study demonstrated that RPHs have antioxidant, antihyaluronidase, and antityrosinase activities for future cosmetic applications.

Exploring Molecular Insights of Cereal Peptidic Antioxidants in Metabolic Syndrome Prevention

The prevalence of metabolic syndrome (MetS) is presently an alarming public health problem globally. Oxidative stress has been postulated to be strongly correlated with MetS, such as type 2 diabetes, obesity, hypertension, cardiovascular diseases, and certain cancers. Cereals are important staple foods which account for a huge proportion of the human diet. However, owing to recent growing demand and the search for natural antioxidants for the prevention and management of MetS, cereal peptides have gained increasing attention for developing functional ingredients or foods with substantial antioxidant properties. This review explores the current production techniques for cereal peptidic antioxidants and their potential mechanism of action in the prevention and management of MetS.

Applications and analysis of hydrolysates in animal cell culture

Animal cells are used in the manufacturing of complex biotherapeutic products since the 1980s. From its initial uses in biological research to its current importance in the biopharmaceutical industry, many types of culture media were developed: from serum-based media to serum-free to protein-free chemically defined media. The cultivation of animal cells economically has become the ultimate goal in the field of biomanufacturing. Serum serves as a source of amino acids, lipids, proteins and most importantly growth factors and hormones, which are essential for many cell types. However, the use of serum is unfavorable due to its high price tag, increased lot-to-lot variations and potential risk of microbial contamination. Efforts are progressively being made to replace serum with recombinant proteins such as growth factors, cytokines and hormones, as well as supplementation with lipids, vitamins, trace elements and hydrolysates. While hydrolysates are more complex, they provide a diverse source of nutrients to animal cells, with potential beneficial effects beyond the nutritional value. In this review, we discuss the use of hydrolysates in animal cell culture and briefly cover the composition of hydrolysates, mode of action and potential contaminants with some perspectives on its potential role in animal cell culture media formulations in the future.

An overview on antioxidant peptides from rice bran proteins: extraction, identification, and applications

Rice by-products, generated through the milling processes, have recently been recognized as a potential source of bioactive compounds, such as proteins, essential amino acids, and phenolics. Owing to their antioxidant capacity (which improve the storage stability of foods), these compounds have gained much attention because of their beneficial impacts on human health. It has to be noted that large quantities of rice by-products are not efficiently utilized, which may result in industrial wastes and environmental consequences. Thence, the aim of this review is to provide a comprehensive insight on the antioxidant capabilities, extraction, identification, functional attributes, and applications of bioactive hydrolysates and peptides derived from rice bran protein. This overview would provide an insight on rice bran proteins, which are abundant in bioactive peptides, and could be used as value-added products in food and pharmaceutical applications. Inclusion of bioactive peptides to prevent food spoilage while maintaining food safety has also been highlighted.

Production and Characterization of Antioxidative Hydrolysates and Peptides from Corn Gluten Meal Using Papain, Ficin, and Bromelain

There has been a growing interest in developing natural antioxidants with high efficiency and low cost. Bioactive protein hydrolysates could be a potential source of natural and safer antioxidants. The objectives of this study were to hydrolyze corn gluten meal using three plant-derived proteases, namely papain, ficin, and bromelain, to produce antioxidative hydrolysates and peptides and to characterize the antioxidant performances using both chemical assays and a ground meat model. The optimum hydrolysis time for papain was 3 h, and for ficin and bromelain was 4 h. The hydrolysates were further separated by sequential ultrafiltration to 5 hydrolysate fractions named F1 to F5 from low molecular weight (MW) (<1 kDa) to high MW range (>10 kDa), which were further characterized for TPC, free radical scavenging capacity against DPPH and ABTS, and metal chelating activity. The fraction F4 produced by papain (CH-P4), F1 produced by ficin (CH-F1), and F3 produced by bromelain (CH-B3) showed the strongest antioxidant activity and yield, respectively. These three fractions were incorporated into ground pork to determine their inhibition effects on lipid oxidation during a 16-day storage period. The inhibition effect was enhanced with the addition of higher amount of hydrolysate (e.g., 1000 vs. 500 mg/kg). The CH-P4 reduced lipid oxidation in ground meat by as much as 30.45%, and CH-B3 reduced oxidation by 27.2% at the same level, but the inhibition was only 13.83% with 1000 mg/kg of CH-F1. The study demonstrated that CGM protein hydrolysates and peptides could be used as naturally derived antioxidant in retarding lipid oxidation and improving product storage stability.

Microbial Fermentation of Industrial Rice-Starch Byproduct as Valuable Source of Peptide Fractions with Health-Related Activity

The rice-starch processing industry produces large amounts of a protein-rich byproducts during the conversion of broken rice to powder and crystal starch. Given the poor protein solubility, this material is currently discarded or used as animal feed. To fully exploit rice's nutritional properties and reduce this waste, a biotechnological approach was adopted, inducing fermentation with selected microorganisms capable of converting the substrate into peptide fractions with health-related bioactivity. Lactic acid bacteria were preferred to other microorganisms for their safety, efficient proteolytic system, and adaptability to different environments. Peptide fractions with different molecular weight ranges were recovered from the fermented substrate by means of cross-flow membrane filtration. The fractions displayed in vitro antioxidant, antihypertensive, and anti-tyrosinase activities as well as cell-based anti-inflammatory and anti-aging effects. In the future, the peptide fractions isolated from this rice byproduct could be directly exploited as health-promoting functional foods, dietary supplements, and pharmaceutical preparations. The suggested biotechnological process harnessing microbial bioconversion may represent a potential solution for many different protein-containing substrates currently treated as byproducts (or worse, waste) by the food industry.

Chromium and arsenic speciation analysis in meats by HPLC-ICP-MS in the presence of hydrolyzed oat proteins with radical scavenging activities

Transition metals play an important role in a wide variety of biological processes, but their functions are dependent on the quantity and the type of species present. Specific forms of arsenic (As) and chromium (Cr) are associated with oxidative stress, cellular damage and inflammation. The aim of this research was to test in a food system whether, in the presence of hydrolyzed oat proteins, arsenic or chromium will exist predominantly in a specific oxidative state, and to evaluate the potential implication of promoting or decreasing oxidative stress. Eight hydrolyzed proteins with different degrees of radical scavenging activities were produced by combining two extraction methods and four proteases. The addition of hydrolysates to ground chicken meat decreased lipid hydroperoxides by up to 50% when stored at 4 °C but had no effect at -20 °C. The ratio of pentavalent arsenic (As(V)) to arsenobetaine (AsB) in meat was about 2:1 but in the presence of the hydrolysates, meanwhile, the amount of AsB detected was 3-fold higher depending on the storage condition. This was due to better extraction of AsB in the presence of hydrolysates rather than to the conversion of other species. Data on chromium showed that Cr(VI) contents decreased from 14.3 ± 0.1 to 6.3 ± 0.5 μg/g while concentrations of Cr(III) increased from 2.8 ± 0. 2 to 8.6 ± 0.7 μg/g. In summary, the addition of hydrolyzed oat proteins to chicken meat enhanced the extraction of AsB, and had little effect on arsenic speciation during storage meanwhile, there was a reduction of Cr(VI) to Cr(III) which was in part due to the relative content of thiol groups. Additionally, there was a reduction of lipid oxidation in meats that contained the oat protein hydrolysates.

Antioxidant properties and potential mechanisms of hydrolyzed proteins and peptides from cereals

Cereals like wheat, rice, corn, barley, rye, oat, and millet are staple foods in many regions around the world and contribute to more than half of human energy requirements. Scientific publications contain evidence showing that apart from energy, the regular consumption of whole grains is useful for the prevention of many chronic diseases associated with oxidative stress. Biological activities have mostly been attributed to the presence of glucans and polyphenols. In recent years however, food proteins have been investigated as sources of peptides that can exert biological functions, promote health and prevent oxidative stress. This review focuses on the role of hydrolyzed proteins and peptides with antioxidant properties in various models and their mechanisms which include hydrogen or electron transfer, metal chelating, and regulation of enzymes involved in the oxidation-reduction process.

Structural and functional properties of food protein-derived antioxidant peptides

The aim of this work is to provide a timely examination of the structure-activity relationship of antioxidative peptides. The main production approach involves enzymatic hydrolysis of animal and plant proteins to produce protein hydrolyzates, which can be further processed by membrane ultrafiltration into size-based peptide fractions. The hydrolyzates and peptide fractions can also be subjected to separation by column chromatography to obtain pure peptides. Although the structural basis for enhanced antioxidant activity varies, protein hydrolyzates and peptide fractions that contain largely low molecular weight peptides have generally been shown to be potent antioxidants. In addition to having hydrophobic amino acids such as Leu or Val in their N-terminal regions, protein hydrolyzates, and peptides containing the nucleophilic sulfur-containing amino acid residues (Cys and Met), aromatic amino acid residues (Phe, Trp, and Tyr) and/or the imidazole ring-containing His have been generally found to possess strong antioxidant properties. PRACTICAL APPLICATIONS: High levels of reactive oxygen species (ROS) in addition to the presence of metal cations can lead to oxidative stress, which promotes reactions that cause destruction of critical cellular biopolymers, such as proteins, lipids, and nucleic acids. Oxidative stress could be due to insufficient levels of natural cellular antioxidants, which enables accumulation of ROS to toxic levels. A proposed approach to ameliorating oxidative stress is the provision of exogenous peptides that can be consumed to complement cellular antioxidants. Food protein-derived peptides consist of amino acids joined by peptides bonds just like glutathione, a very powerful natural cellular antioxidant. Therefore, this review provides a timely summary of the in vitro and in vivo reactions impacted by antioxidant peptides and the postulated mechanisms of action, which could aid development of potent antioxidant agents. The review also serves as a resource material for identifying novel antioxidant peptide sources for the formulation of functional foods and nutraceuticals.

Optimization of the enzymatic hydrolysis of rice protein by different enzymes using the response surface methodology

The optimization of the enzymatic hydrolysis of rice protein was determined using an experimental design tool. The semi-purified protease of Bacillus licheniformis LBA 46 and commercial protease Alcalase 2.4 L were used to produce rice hydrolysates using pH values ranging from 6 to 10 and enzyme concentrations varying from 50 to 150 U/mL. The optimized conditions were validated, and using the chosen conditions (pH 10 and 100 U/mL of protease), it was possible to confirm that the model was predictive for oxygen radical absorbance capacity (ORAC) and ferric reducing antioxidant power (FRAP) responses. The experimental values for the ORAC and FRAP responses were 940 and 18.78 TE µmol/g for the rice protein hydrolysates prepared with LBA protease and 1001.94 and 19.31 TE µmol/g for the rice protein hydrolysates prepared with Alcalase 2.4 L. After optimization of the enzymatic hydrolysis conditions, the antioxidant activity values increased when compared to the values for the intact rice protein: 324.97 TE µmol/g (ORAC) and 6.14 TE µmol/g (FRAP). It was also observed that the LBA protease had an action similar to the commercial protease, showing its potential for application in protein hydrolysis.

Fractionation and antioxidant properties of rice bran protein hydrolysates stimulated by in vitro gastrointestinal digestion

Rice bran was used as a starting material to prepare protein concentrate through enzyme-assisted extraction. The hydrolysis of protein concentrate under in vitro gastrointestinal digestion (pepsin-trypsin system) greatly improved the antioxidant properties. Rice bran protein hydrolysate was further fractionated by membrane ultrafiltration (UF, F1: molecular weight (MW) <3kDa, F2: MW 3-5kDa, and F3: MW 5-10kDa). Peptides with smaller MW possessed higher antioxidant activities (P<0.05). UF showed a great efficacy to selectively separate the metal-chelating peptides. Tyrosine and phenylalanine had positive correlations with their DPPH & ABTS radicals scavenging activities and ferric reducing antioxidant power (r>0.831). A major peptide fragment was detected at m/z 1088 by a MALDI-TOF mass spectrometry. There is high potential that antioxidative peptides from rice bran might also be produced in the gastrointestinal tract of the human body.

In Vitro Antioxidant Activity and In Vivo Anti-Fatigue Effect of Sea Horse (Hippocampus) Peptides

This study investigated changes the in vitro antioxidant activity of Hippocampus polypeptides during enzymatic hydrolysis, including the effects of enzyme species, enzyme concentration, material-liquid ratio, hydrolysis time, pH, and temperature of the reaction system. Its in vivo anti-fatigue activity was also studied. Hippocampus peptide prepared by papain digestion exhibited the highest 1,1-diphenyl-2-picryl-hydrazyl free radical scavenging rate (71.89% ± 1.50%) and strong hydroxyl radical scavenging rate (75.53% ± 0.98%), compared to those prepared by five other commonly used enzymes (i.e., trypsin, neutral protease, compound protease, flavorzyme, and alkaline protease). Additionally, maximum antioxidant activity of Hippocampus polypeptide prepared by papain digestion was reached after hydrolysis for 40 min at pH 6.0 and 60 °C of the reaction system by using 2000 U/g enzyme and a material-liquid ratio of 1:15. Moreover, compared with the control group, Hippocampus peptide prolonged the swimming time by 33%-40%, stabilized the blood glucose concentration, increased liver glycogen levels, and decreased blood lactate levels and blood urea nitrogen levels in mice (p < 0.01). In conclusion, these results indicated that Hippocampus polypeptide prepared by papain digestion under optimal conditions exhibited high degrees of antioxidant and anti-fatigue activity.

Protective effects of rice dreg protein hydrolysates against hydrogen peroxide-induced oxidative stress in HepG-2 cells

In this paper, the effects of rice dreg protein hydrolysates (RDPHs) obtained by various proteases on hydrogen peroxide-induced oxidative stress in HepG-2 cells were investigated.

Biologically active peptides: Processes for their generation, purification and identification and applications as natural additives in the food and pharmaceutical industries

Recent technological advances have created great interest in the use of biologically active peptides. Bioactive peptides can be defined as specific portions of proteins with 2 to 20 amino acids that have desirable biological activities, including antioxidant, anti-hypertensive, antithrombotic, anti-adipogenic, antimicrobial and anti-inflammatory effects. Specific characteristics, including low toxicity and high specificity, make these molecules of particular interest to the food and pharmaceutical industries. This review focuses on the production of bioactive peptides, with special emphasis on fermentation and enzymatic hydrolysis. The combination of different technologies and the use of auxiliary processes are also addressed. A survey of isolation, purification and peptide characterization methods was conducted to identify the major techniques used to determine the structures of bioactive peptides. Finally, the antioxidant, antimicrobial, anti-hypertensive, anti-adipogenic activities and probiotic-bacterial growth-promoting aspects of various peptides are discussed.

Amaranth peptides from simulated gastrointestinal digestion: antioxidant activity against reactive species

We evaluated the capacity of simulated gastrointestinal digests or alcalase hydrolysates of protein isolates from amaranth to scavenge diverse physiologically relevant reactive species. The more active hydrolysate was obtained with the former method. Moreover, a prior alcalase treatment of the isolate followed by the same simulated gastrointestinal digestion did not improve the antioxidant capacity in any of the assays performed and even produced a negative effect under some conditions. Gastrointestinal digestion produced a strong increment in the scavenging capacity against peroxyl radicals (ORAC assay), hydroxyl radicals (ESR-OH assay), and peroxynitrites; thus decreasing the IC50 values to approximately 20, 25, and 20%, respectively, of the levels attained with the nonhydrolyzed proteins. Metal chelation (HORAC assay) also enhanced respect to isolate levels, but to a lesser extent (decreasing IC50 values to only 50%). The nitric-oxide- and superoxide-scavenging capacities of the digests were not relevant with respect to the methodologies used. The gastrointestinal digests from amaranth proteins acted against reactive species by different mechanisms, thus indicating the protein isolate to be a potential polyfunctional antioxidant ingredient.

Radical Scavenging Activities and Lipid Peroxidation Inhibition of Okara Protein Hydrolysates Prepared with Proteases and Sequential UF

Okara protein isolate was hydrolyzed by two stages enzyme hydrolysis (Protamex+Flavourzyme, Pro+Fla ) and further separated by sequential ultrafiltration (UF) to four fractions (P1~P4). The 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity of the P3 fraction (1kDa < MW < 3kDa) is 24.6 mmol trolox equivalent (TE)/g peptide and the inhibitory activity is 84.2% at 10 mg/mL. The hydroxyl radical scavenging activity is 85.4% at the same concentration. Pro+Fla-P3 was incorporated into ground beef to determine their effect on lipid oxidation during a 15-day storage period. Pro+Fla-P3 fraction at 500 μg/g significantly inhibited lipid oxidation by 20.8% and 18.2% at day 8 and 15 of storage. The concentration at 250 μg/g could not significantly inhibit lipid oxidation at 15 day. It suggests that okara protein hydrolysates could be developed and used to improve shelf-life of meat products.

Role of oxidative stress in infectious diseases. A review

Oxidative stress plays a dual role in infections. Free radicals protect against invading microorganisms, and they can also cause tissue damage during the resulting inflammation. In the process of infection, there is generation of reactive species by myeloperoxidase, NADPH oxidase, and nitric oxide synthase. On the other hand, reactive species can be generated among others, by cytochrome P450, some metals, and xanthine oxidase. Some pathologies arising during infection can be attributed to oxidative stress and generation of reactive species in infection can even have fatal consequences. This article reviews the basic pathways in which reactive species can accumulate during infectious diseases and discusses the related health consequences.