Impact of ultrasound on egg white proteins as a pretreatment for functional hydrolysates production

Thermal gelation and digestion properties of hen egg white: Study on the effect of neutral and alkaline salts addition

In this study, the thermal gelation and digestion properties of hen egg white (hen EW) proteins with different salts were investigated. Results show that the addition of neutral salt - sodium chloride (NaCl) decreased the gel hardness/resilience, increased gel lightness, aggregated particle size and digestibility of hen EW proteins significantly. In contrast, alkaline salts - phosphate and carbonate addition increased the gel resilience and strain tolerance as well as reduced the aggregated particle size and gel lightness of hen EW proteins due to the increase of solution pH and negative charge. Correlation analysis shows that the digestibility of hen EW gels was affected by gel viscoelasticity, molecule forces and texture. In conclusion, thermal gelation properties of hen EW proteins could be modulated by salts with different pH/ionic strength, and thus affected the protein digestion and peptide released.

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.

Impact of Different Enzymatic Processes on Antioxidant, Nutritional and Functional Properties of Soy Protein Hydrolysates Incorporated into Novel Cookies

Soy protein concentrate (SPC) was hydrolyzed using several commercial food-grade proteases (Alcalase, Neutrase, papain, Everlase, Umamizyme, Flavourzyme) and their combination to obtain promising ingredients in the manufacture of functional bakery products. In all cases, the hydrolysis caused nutritional, sensory, and rheological changes in SPC, as well as protein structural changes like increased surface hydrophobicity and content of exposed SH groups with the magnitude of these changes depending on enzyme specificity. The hydrolysis with the combination of Neutrase and Flavourzyme (NeuFlav) increased essential amino acid content by 9.8% and that of Lys by 32.6% compared to SPC. This hydrolysate showed also significant antioxidant activities including ABTS and superoxide anion scavenging activity and metal-chelating ability. The addition of all hydrolysates in wheat flour decreased water adsorption and increased development time to some extent due to gluten network weakening, but also decreased the rate of starch retrogradation, contributing to the increase of the shelf-life of bakery products. The NeuFlav tasted less bitter than other hydrolysates, while E-nose provided a discrimination index of 93 between control and hydrolysates. It appeared that the addition of the NeuFlav hydrolysate in a cookie formulation improved protein content and nutritional quality and directed to its higher general consumer acceptability than cookies formulated with only wheat flour.

Ultrasound-assisted alkaline proteinase extraction enhances the yield of pecan protein and modifies its functional properties

To enhance the extraction yield of pecan protein and modify its functional properties, this study investigated whether both ultrasound and enzyme have a synergistic impact on the extraction of pecan (Carya illinoinensis (Wangenh.) K. Koch) protein. The highest protein extraction rate (25.51%) was obtained under the conditions of 1415.43 W.cm-2, 15 min, pH 10.0, 50 °C, and 1% (w/w) alkaline proteinase. Owing to its high shear, mechanical energy and cavitation, the ultrasound process increased the solubility of the substrate making it readily accessible to the enzyme, thereby accelerating the chemical reaction and improving the yield of the protein. The optimized ultrasound-assisted enzymatic method (400 W, 20 kHz, 5 s/3s) effectively changed the secondary and tertiary structure of the pecan protein. The results of surface hydrophobicity, intrinsic fluorescence spectra, sulfhydryl content and scanning electron microscopy all indicated the unfolding of protein and exposure of hydrophobic groups and sulfhydryl groups. Moreover, the protein obtained by this method showed higher solubility (70.77%), higher emulsifying activity (120.56 m2/g), smaller particle size (326.7 nm), and better dispersion (0.305) than single ultrasound and non-ultrasound methods (p < 0.05). To conclude, ultrasound-assisted enzymatic method could be an appropriate technique to improve the yield and quality of the pecan protein. The study also provides a theoretical basis for the application of pecan protein in food processing.

Whey protein isolate-gum Acacia Maillard conjugates as emulsifiers for nutraceutical emulsions: Impact of glycation methods on physicochemical stability and in vitro bioaccessibility of β-carotene emulsions

The physicochemical stability and in vitro bioaccessibility of β-carotene emulsions stabilized by the whey protein isolate (WPI)-gum Acacia (GA) conjugates prepared by dry-heating (Con WPI (D)) and ultrasound (Con WPI (U)) Maillard reaction were investigated in this study. The conjugate-stabilized emulsions have a larger mean size than the WPI-stabilized emulsion. The stability of emulsions under freeze-thaw treatment, high ionic strength conditions, thermal treatment and pH conditions near the isoelectric point of WPI were improved by glycation. The chemical stability of β-carotene in emulsions was also enhanced by WPI-GA conjugates. The WPI-GA conjugate-stabilized emulsions have better stability for droplet aggregation during in vitro simulated gastrointestinal digestion, which increased β-carotene bioaccessibility. However, the Con WPI (U)-stabilized emulsion shows poor thermal stability and lower β-carotene bioaccessibility than the Con WPI (D)-stabilized emulsion, which may be attributed to ultrasound-induced structural changes during the process of glycation.

Preparation and in vitro bioactive evaluation of cashew-nut proteins hydrolysate as a potential source of anti-allergy peptides

This work proposes a novel potential source of antiallergens based on bioactive peptides. Cashew-nut protein hydrolysate with antiallergic activity was prepared from cashew nuts through protease treatment. The change in the antiallergic activity of cashew-nut protein hydrolysate during in vitro simulated digestion was investigated. Cashew-nut protein hydrolysates were prepared through treatment using five different enzymes, namely, Alcalase, Protamex, Neutrase, papain, and bromelin. According to the results of molecular weight distribution, more small molecular weight peptides could be obtained by selecting Alcalase protease than other proteases, and the degree of hydrolysis, trichloroacetic acid-soluble peptide yield and hyaluronidase inhibitory rate of the hydrolysate were 17.0 ± 61.52%, 26.28 ± 0.13% and 62.06% ± 5.07%, which were significantly higher than those of other proteases. Therefore, Alcalase is the most suitable protease for the preparation of cashew-nut hydrolysates. Cashew-nut protein hydrolysates prepared with Alcalase under optimum conditions were fractionated through ultrafiltration. Fractions with low molecular weight exhibited the highest hyaluronidase inhibitory rate (90.57%) among all fractions. The inhibition of hyaluronidase activity during digestion showed that cashew-nut protein hydrolysate III (CPH III) has persistent antiallergic activity. Therefore, CPH III could serve as a potential source of functional peptides with health-promoting effects.

Synergistic Effect of Enzyme Hydrolysis and Microwave Reactor Pretreatment as an Efficient Procedure for Gluten Content Reduction

In this study, we assessed the effects of microwave irradiation of wheat gluten proteins as a pretreatment performed in a microwave reactor that could accurately control process parameters as a function of power and temperature, as well as comparing it with conventional heat treatment. The aim was to identify suitable combinations of partial enzymatic hydrolysis and microwave pretreatment parameters to produce gluten hydrolysates with reduced allergenicity and conserved techno-functional features for food application. FTIR analysis, and total and reactive SH group contents confirmed that the microwave-controlled heating can significantly change the secondary structure and conformation of gluten protein. The microwave treatment had the largest effect at 200 W and 100 °C, at which the content of gluten has been reduced by about 2.5-fold. The microwave pretreatment also accelerated the enzymatic hydrolysis of gluten, changing the kinetic profile. The apparent hydrolysis rate constants (k₂) were 1.00, 3.68, 3.48, 4.64 and 4.17 min⁻¹ for untreated gluten, and those pretreated with microwave power of 200, 400, 600 and 800 W, respectively. Compared to the heat treatment, it appeared that microwave specific non-thermal effects had a significant influence on the gluten structure and allergenicity and, in combination with the enzymatic hydrolysis, ultimately yielded protein hydrolysates with enhanced antioxidant and functional properties.

Degree of hydrolysis, functional and antioxidant properties of protein hydrolysates from Grass Turtle (Chinemys reevesii) as influenced by enzymatic hydrolysis conditions

Grass turtle muscle was hydrolyzed with papain enzyme to produce protein hydrolysate (PH) and the degree of hydrolysis (DH) was determined. Under optimal conditions, the highest DH was 19.52% and the yield was recorded as 17.26%. Protein content of the hydrolysates was ranged from 73.35% to 76.63%. Total amino acids were more than 96.77% for each PH. The PH obtained at DH 19.52% achieved excellent solubility and emulsifying activity which were 95.56% and 108.76 m2/g, respectively at pH 6. Foam capacity amounted 100% in PH of DH 19.52% at pH 2, and water-holding capacity was 4.38 g/g. The antioxidant activity showed the strongest hydroxyl radical scavenging activity (95.25%), ABTS (84.88%), DPPH (75.89%), iron chelating (63.25%), and cupper chelating (66.90%) at DH 11.96%, whereas reducing power (0.88) at DH 19.52%. Thus, the findings indicated that utilization of grass turtle muscle protein hydrolysate is a potential alternative protein resource to improve the nutritional and functional properties in food ingredients and product formulations.

Processes for reducing egg allergenicity: Advances and different approaches

Egg is a versatile ingredient and ubiquitous food. Nevertheless, egg proteins are a common cause of allergy mainly in childhood. Until now, egg eviction has been the best way to prevent this disorder, however, processed food can contribute to mitigate allergies and to guarantee life quality of allergic individuals. This review focuses on discussing and highlighting recent advances in processes to reduce egg allergenicity as well as new approaches to egg allergy management. In recent times, different methods have been developed to reduce egg allergies, by hiding the epitopes or changing the native or conformational structure of the proteins. Despite processing food has not yet been a solution to completely remove the allergenic potential of egg proteins, innovative strategies, such as addition of phenolic compounds, have been developed with promising results.

Immobilized Alcalase on Micron- and Submicron-Sized Alginate Beads as a Potential Biocatalyst for Hydrolysis of Food Proteins

Enzymatic hydrolysis of food proteins is convenient method to improve their functional properties and physiological activity. Herein, the successful covalent attachment of alcalase on alginate micron and submicron beads using the carbodiimide based chemistry reaction and the subsequent application of the beads for egg white and soy proteins hydrolysis were studied. In addition to the electrostatic extrusion technique (EE) previously used by others, the potential utilization of a novel ultrasonic spray atomization technique without drying (UA) and with drying (UAD) for alginate submicron beads production has been attempted. The immobilization parameters were optimized on microbeads obtained by EE technique (803 ± 23 µm) with respect to enzyme loading and alcalase activity. UA and UAD techniques resulted in much smaller particles (607 ± 103 nm and 394 ± 51 nm in diameter, respectively), enabling even higher enzyme loading of 671.6 ± 4 mg g−1 on the carrier and the highest immobilized alcalase activity of 2716.1 IU g−1 in the standard reaction. The UAD biocatalyst exhibited also better performances in the real food system based on egg white or soy proteins. It has been shown that the immobilized alcalase can be reused in seven successive soy protein hydrolysis cycles with a little decrease in the activity.

Chicken Egg Proteins and Derived Peptides with Antioxidant Properties

In addition to their high nutritional value, some chicken egg proteins and derivatives such as protein hydrolysates, peptides and amino acids show antioxidant properties which make them prominent candidates for the development of functional foods, drawing attention to both the food and biopharmaceutical industries. This review summarizes current knowledge on antioxidant activity of chicken egg proteins and their derived peptides. Some egg proteins such as ovalbumin, ovotransferrin and lysozyme from egg white or phosvitin from yolk have shown antioxidant properties, although derived peptides have higher bioactive potential. The main process for obtaining egg bioactive peptides is enzymatic hydrolysis of its proteins using enzymes and/or processing technologies such as heating, sonication or high-intensity-pulsed electric field. Different in vitro assays such as determination of reducing power, DPPH and ABTS radical-scavenging activity tests or oxygen radical absorbance capacity assay have been used to evaluate the diverse antioxidant mechanisms of proteins and peptides. Similarly, different cell lines and animal models including zebrafish, mice and rats have also been used. In summary, this review collects all the knowledge described so far regarding egg proteins and derived peptides with antioxidant functions.

Double enzyme hydrolysis for producing antioxidant peptide from egg white: Optimization, evaluation, and potential allergenicity

Egg white is a good source of high-quality proteins in food products and an excellent source of antioxidant active peptides through hydrolysis. The hydrolysis conditions for the preparation of potent antioxidant peptides from egg white with chymotrypsin and pepsin were optimized by the response surface methodology. The antioxidant activity and potential allergenicity of the prepared peptides were evaluated by the oxidative damage model and IgE-binding capability, respectively. After ultrafiltration, the peptide produced using the optimized parameters (preheating time of 3.16 hr, hydrolysis time of 3 hr, a sample/solution ratio of 10%, multiple enzymes ratio (E1/E2) of 1.7:1, and E/S of 0.4%) showed antioxidant activity of was 30.86 μmol AAE/g DW and with low potential for allergenicity. The optimized method is efficient and economical and may be applied to the industrial production of antioxidant peptides to obtain nutraceutical and pharmaceutical agents with low sensitivity. However, further in vivo studies must be conducted. PRACTICAL APPLICATIONS: Egg is consumed as an excellent source of protein. Antioxidant peptides released from egg white is considered to be used in food preservation and human health. Few researches on the optimization of egg peptides were aimed to obtain practical techniques used in the food industry. In this paper, egg white hydrolysis peptide with high antioxidant property and low potential allergenicity was prepared after the optimization of double enzyme hydrolysis. The products could be a natural health care products derived from a dietary source and considered using in additive during food production and health food. And the methods used are economical and energy-saving and could be developed to utilize in the food industry.

Fabrication of (-)-epigallocatechin-3-gallate carrier based on glycosylated whey protein isolate obtained by ultrasound Maillard reaction

This study investigated the effect of glycation on the binding of whey protein isolate (WPI) with (-)-epigallocatechin-3-gallate (EGCG), and the physicochemical stability and bioaccessibility of the formed complex. The WPI-gum Acacia (GA) conjugate was prepared by ultrasound-assisted Maillard reaction. Results indicated that conjugated WPI showed stronger binding and entrapping ability to EGCG than that of WPI. The protein aggregation induced by EGCG was partly inhibited by glycosylation, presumably due to the steric hindrance of polysaccharide chains. The greatest protection of EGCG and its antioxidant activity were also obtained by complexing it with WPI-GA conjugate. The in vitro bioaccessibility analysis demonstrated that the bioaccessibility of EGCG cloud be significantly (p < 0.05) enhanced by complexing it with WPI, especially WPI-GA conjugate. These findings are important to design promising and effective EGCG carriers for its wide application in food industry.

Techno-functional attribute and antioxidative capacity of edible insect protein preparations and hydrolysates thereof: Effect of multiple mode sonochemical action

Hermetia illucens (edible insect) larvae protein, and hydrolysates were prepared using three pretreatment modes (conventional, fixed-frequency ultrasonic, and sweep-frequency). Protein subunit scores, microstructure, antioxidative activity, and techno-functional property of the respective isolates and hydrolysates were investigated. Alkaline protease hydrolysis significantly enhanced protein solubility, but impaired the emulsifying property and foaming stability. Isolates and hydrolysates treated by ultrasound exhibited highest antioxidative effect, and showed excellent solubility and foam expansion over wide (2-12) pH, likened the conventional. Ultrasonic, particularly sweep-frequency, treated hydrolysates overall showed superior solubility, foam, and antioxidative (ABTS, Superoxide scavenging, and Ferric-reducing) capacity than the remaining modes and isolates (p < 0.05). Treatment type influenced microstructure, functional attributes and antioxidative capacity of hydrolysates and isolates. Thus, functional/antioxidative property could be improved or modified for different food applications based on elected treatment. H. illucens isolate and hydrolysate preparations thereof could suitably be used in development of novel food formulations.

Modifying the Functional Properties of Egg Proteins Using Novel Processing Techniques: A Review

Egg proteins can be used in a wide range of food products, owing to their excellent foaming, emulsifying, and gelling properties. Another important functional property is the susceptibility of egg proteins to enzymatic hydrolysis, as protein digestion is closely related to its nutritional value. These functional properties of egg proteins are likely to be changed during food processing. Conventional thermal processing can easily induce protein denaturation and aggregation and consequently reduce the functionality of egg proteins due to the presence of heat-labile proteins. Accordingly, there is interest from the food industry in seeking novel nonthermal or low-thermal techniques that sustain protein functionality. To understand how novel processing techniques, including high hydrostatic pressure, pulsed electric fields, ionizing radiation, ultraviolet light, pulsed light, ultrasound, ozone, and high pressure homogenization, affect protein functionality, this review introduces the mechanisms involved in protein structure modification and describes the structure-functionality relationships. Novel techniques differ in their mechanisms of protein structure modification and some have been shown to improve protein functionality for particular treatment conditions and product forms. Although there is considerable industrial potential for the use of novel techniques, further studies are required to make them a practical reality, as the processing of egg proteins often involves other influencing factors, such as different pH and the presence of other food additives (for example, salts, sugar, and polysaccharides).

Effects of slit divergent ultrasound and enzymatic treatment on the structure and antioxidant activity of arrowhead protein

The arrowhead has attracted great research interest for their potential applications in pharmacy, food and biomedical areas. However, no information is reported about the nature and structure of the arrowhead protein (AP). Herein, effects of slit divergent ultrasound (28, 33, 40 KHz frequencies at 30-50 °C) and enzymatic (pepsin, trypsin, and alcalase) treatment on structure of AP were studied. In addition, changes in antioxidant activity of AP treated with ultrasound and enzymes were measured by chemical and cellular-based assays. The results showed that ultrasound treatment had considerable impact on the structure of AP and increased the susceptibility of AP to pepsin, trypsin and alcalase proteolysis. The changes in UV-Vis spectra, free sulfhydryl (SH) and disulfide bonds (SS) groups indicated that the structure of AP unfolded after ultrasound treatment. Besides, intrinsic fluorescence intensity of AP was increased by ultrasound treatment and then decreased after following enzymatic treatment. The circular dichroism (CD) analysis showed that ultrasound and enzymatic treatment decreased α-helix, β-turn of content of AP. However, the β-sheet and random coil content of AP increased. Interestingly, the AP after ultrasound and enzymatic treatment showed significant higher anti-oxidative activity in RAW 264.7 cells (p < 0.05) in comparison with control. In conclusion, the slit divergent ultrasonic provides a powerful endorsement for increasing the proteolysis of AP. Moreover, the improvement of the antioxidant activity of AP enzymatic hydrolysates provides a foundation of developing new type of plant-derived antioxidant peptides application.

Characterization of heat-stable whey protein: Impact of ultrasound on rheological, thermal, structural and morphological properties

Ultrasound, an emerging non-thermal technique, has potential to modify the functionality of bio-molecules like protein. In the present study, the impact of ultrasound on whey protein (WP) was assessed with functional, rheological, heat coagulation and transition temperature, SDS-PAGE, FTIR spectra, scanning electron microscopy and transmission electron microscopy. The results of this study showed that the raw WP had broad bimodal particle size distribution while after ultrasonication, modified WP exhibited narrower distribution along with smaller particle size (0.683 ± 0.225 μm) compared to untreated WP (2.453 ± 0.717 μm). The solubility of WP also increased after ultrasonication (72.22 ± 0.68% to 79.21 ± 1.08%). During the rheological evaluation, both the samples exhibited Newtonian behaviour but, the modified WP exhibited dramatically higher storage modulus (G') throughout the temperature profile compared to raw WP mainly due to enhanced proteins aggregation during heating which revealed more elastic and stronger gel. The modified WP exhibited significantly higher (about 6-times) heat stability compared to raw WP which signified that after ultrasonication the WP can withstand higher temperature during processing for longer time. The results were also confirmed by higher transition temperature (T_peak) of modified WP (93.32°) compared to untreated WP (81.93 °C). The SDS-PAGE profile of raw and modified WP showed that the ultrasound significantly decreased the bands density of low molecular weight molecules (β-lactoglobulin and α-lactalbumin). FTIR spectra also showed noticeable difference between the secondary structure component of raw and modified WP. Finally, the structural micrographs of raw and modified WP from SEM and TEM analysis also confirmed the adequacy of modification of WP employing non-thermal techniques. The modified WP revealed smaller, regular and more homogenous and ordered structures compared to untreated sample.

Production of egg white protein hydrolysates with improved antioxidant capacity in a continuous enzymatic membrane reactor: optimization of operating parameters by statistical design

This study focuses on the influence of operating conditions on Alcalase-catalyzed egg white protein hydrolysis performed in a continuously stirred tank reactor coupled with ultrafiltration module (10 kDa). The permeate flow rate did not significantly affect the degree of hydrolysis (DH), but a significant increase in process productivity was apparent above flow rate of 1.9 cm³ min^-1. By contrast, an increase in enzyme/substrate (E/S) ratio provided an increase in DH, but a negative correlation was observed between E/S ratio and productivity. The relationship between operating conditions and antioxidant properties of the hydrolysates, measured by three methods, was studied using Box-Behnken experimental design and response surface methodology. The statistical analysis showed that each variable (impeller speed, E/S ratio, and permeate flow rate) had a significant effect on the antioxidant capacity of all tested systems. Nevertheless, obtained response functions revealed that antioxidative activity measured by DPPH, ABTS and FRAP methods were affected differently by the same operating conditions. High impeller speeds and low permeate flow rates favor ABTS while high impeller speeds and high permeate flow rates had a positive effect on the DPPH scavenging activity. On the other hand, the best results obtained with FRAP method were achieved under moderate operating conditions. The integration of the reaction and ultrafiltration membrane separation in a continuous manner appears to be a right approach to improve and intensify the enzymatic process, enabling the production of peptides with desired antioxidant activity.

Thermal and single frequency counter-current ultrasound pretreatments of sodium caseinate: enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution and antioxidant peptides

BACKGROUND

Due to the disadvantages of traditional enzymolysis, pretreatments are crucial to enhance protein enzymolysis. Enzymolysis kinetics and thermodynamics, amino acids composition, molecular weight distribution, fluorescence spectroscopy and antioxidant activity of thermal (HT) and single frequency counter-current ultrasound (SCFU) pretreated sodium caseinate (NaCas) were studied.

RESULTS

Enzymolysis of untreated NaCas (control) improved significantly (P < 0.05) by SFCU and followed by HT. Values of the Michaelis-Menten constant (K_M ) of SFCU and HT were 0.0212 and 0.0250, respectively. HT and SFCU increased (P < 0.05) the reaction rate constant (k) by 38.64 and 90.91%, respectively at 298 K. k values decreased with increasing temperature. The initial activation energy (46.39 kJ mol^-1 ) reduced (P < 0.05) by HT (39.66 kJ mol^-1 ) and further by SFCU (33.42 kJ mol^-1 ). SFCU-pretreated NaCas hydrolysates had the highest contents of hydrophobic, aromatic, positively and negatively charged amino acids. Medium-sized peptides (5000-1000 Da) are higher in SFCU (78.11%) than HT and the control. SFCU induced molecular unfolding of NaCas proteins. Accordingly, SFCU-pretreated NaCas hydrolysate exhibited the highest scavenging activity on DPPH and hydroxyl radicals, reducing power, and iron chelating ability.

CONCLUSION

SFCU pretreatment would be a useful tool for production of bioactive peptides from NaCas hydrolysate. © 2016 Society of Chemical Industry.

Hen Egg as an Antioxidant Food Commodity: A Review

Intake of antioxidants through diet is known to be important in reducing oxidative damage in cells and improving human health. Although eggs are known for their exceptional, nutritional quality, they are not generally considered as antioxidant foods. This review aims to establish the importance of eggs as an antioxidant food by summarizing the current knowledge on egg-derived antioxidants. Eggs have various natural occurring compounds including the proteins ovalbumin, ovotransferrin and lysozyme in egg white, as well as phosvitin, carotenoids and free aromatic amino acids in egg yolk. Some lipophilic antioxidants such as vitamin E, carotenoids, selenium, iodine and others can be transferred from feed into egg yolk to produce antioxidant-enriched eggs. The bioactivity of egg antioxidants can be affected by food processing, storage and gastrointestinal digestion. Generally thermal processing methods can promote loss of antioxidant properties in eggs due to oxidation and degradation, whereas gastrointestinal digestion enhances the antioxidant properties, due to the formation of new antioxidants (free amino acids and peptides). In summary, in addition to its well-known nutritional contribution to our diet, this review emphasizes the role of eggs as an important antioxidant food.