Effect of Different Heat Treatments on In Vitro Digestion of Egg White Proteins and Identification of Bioactive Peptides in Digested Products

Effect of MDA-mediated oxidation on the protein structure and digestive properties of golden pomfret

In this study, golden pomfret myofibrillar protein (MP) was used as the research object, and the oxidation system of malondialdehyde (MDA) as an inducer and the static digestion model in vitro was established for the analysis of the changes in protein structure and molecular morphology during oxidation and digestion. Subsequently, the effects of MDA-mediated oxidation on the structure and digestive properties of golden pomfret myofibrillar fibrillar protein were determined. The results showed that the hydrolysis degree and digestion rate of MP were inhibited with the increase in MDA concentration (0, 0.5, 1, 2, 5, 10 mmol/L), and the carbonyl group, surface hydrophobicity, irregular curling, and MDA content increased significantly (P < 0.05), whereas the total sulfhydryl groups, α-helices, free amino groups, hydrolysis degree, and MDA incorporation decreased significantly (P < 0.05), The molecular particle size was significantly reduced (P < 0.05), and the molecular morphology and molecular structure were analyzed (P >0.05). Finally, the molecular size and cross-linking degree gradually increased. In conclusion, MDA can alter the structure and morphology of proteins, resulting in a decrease in hydrolysis and digestion rate. This study can provide theoretical support and reference for the regulation of protein digestion.

Albumen and Yolk Plasma Peptidomics for the Identification and Quantitation of Bioactive Molecules and the Quality Control of Hen Egg Products

Hen eggs and the corresponding food products are essential components of human diet. In addition to supplying basic nutrients, they contain functional peptides that are released in vivo within the intact raw material following physiological proteolytic events affecting specific proteins or derive from technological processing of albumen and yolk fractions as a result of the dedicated use of proteases from plant and microbial sources. Besides their potential importance for functional applications, peptides released under physiological conditions in intact egg can be used as markers of product storage and deterioration. Therefore, characterization and quantitation of peptides in egg and egg-derived products can be used to implement evaluation of potential bioactivities as well as to assess food product qualitative characteristics. Here, we provide dedicated information on extraction, identification, and quantitative analysis of peptides from albumen and yolk plasma; nano-liquid chromatography-mass spectrometry combined with bioinformatic analysis of resulting raw data by different software tools allowed to assign molecules based on database searching and to evaluate their relative quantity in different samples.

The Impact of Processing and Extraction Methods on the Allergenicity of Targeted Protein Quantification as Well as Bioactive Peptides Derived from Egg

This review article discusses advanced extraction methods to enhance the functionality of egg-derived peptides while reducing their allergenicity. While eggs are considered a nutrient-dense food, some proteins can cause allergic reactions in susceptible individuals. Therefore, various methods have been developed to reduce the allergenicity of egg-derived proteins, such as enzymatic hydrolysis, heat treatment, and glycosylation. In addition to reducing allergenicity, advanced extraction methods can enhance the functionality of egg-derived peptides. Techniques such as membrane separation, chromatography, and electrodialysis can isolate and purify specific egg-derived peptides with desired functional properties, improving their bioactivity. Further, enzymatic hydrolysis can also break down polypeptide sequences and produce bioactive peptides with various health benefits. While liquid chromatography is the most commonly used method to obtain individual proteins for developing novel food products, several challenges are associated with optimizing extraction conditions to maximize functionality and allergenicity reduction. The article also highlights the challenges and future perspectives, including optimizing extraction conditions to maximize functionality and allergenicity reduction. The review concludes by highlighting the potential for future research in this area to improve the safety and efficacy of egg-derived peptides more broadly.

Unveiling and application of the chicken egg proteome: An overview on a two-decade achievement

Egg proteins are not only the most complete and ideal form of protein for human or embryo nutrition but also play the vital role in the food industry. Egg proteins are subjected to many potential changes under various conditions, which may further alter the nutritional value, physicochemical-properties, and bioactivities of proteins. Recent advances in our understanding of the proteome of raw egg matrix from different species and dynamic changes occurring during storage and incubation are developing rapidly. This review provides a comprehensive overview of the main characteristics of chicken egg proteome, covering all its components and applications under various conditions, such as markers detection, egg quality evaluation, genetic and biological unknown identification, and embryonic nutritional supplementation, which not only contributes to our in-depth understanding of each constituent functionality of proteome, but also provides information to increase the value to egg industry.

WeChat-Based Comprehensive Education on Egg White Protein Intake for Patients Undergoing Peritoneal Dialysis: A Combined Prospective and Retrospective Study

Protein malnutrition is a well-described complication of peritoneal dialysis (PD), a standard mode of treatment for end-stage renal disease (ESRD), and contributes to morbidity, treatment failure, and mortality. To assess the usefulness of WeChat-based education for ensuring optimal protein intake through the consumption of egg white protein, 140 young and middle-aged patients undergoing PD are assigned to either the intervention group or the control group. The results show that reinforcing comprehensive PD education using WeChat can improve nutritional parameters, clinical parameters, and quality of life.

Guided Gradual Egg-Tolerance Induction in Hen's Egg Allergic Children Tolerating Baked Egg: A Prospective Randomized Trial

Background

Over the last few years, studies have shown that the majority of egg allergic children tolerate baked egg (e.g., cake), and that consuming baked egg accelerates the resolution of egg allergy. However, few prospective studies demonstrate the step-wise reintroduction of egg at home after developing baked egg tolerance. Although this could have a positive impact on the children's quality of life and nutrition. Additionally, research supporting the theoretical concept that heating in the presence or absence of wheat causes reduced allergenicity of egg proteins is limited.

Objective

To investigate the clinically most favorable duration of gradual egg-tolerance induction in baked egg tolerant children at home, with regard to complete raw egg tolerance.

Methods

Baked egg tolerant children above 12 months of age were randomly assigned to a short- or long arm protocol. In the short arm, egg-tolerance induction was studied over 18 months compared to 30 months in the long arm. Children were guided through this protocol involving the step-wise introduction of increasingly allergenic forms of egg starting with baked egg offered as cake, followed by hard-boiled egg, omelet/waffle/pancake, soft-boiled egg, and finally raw egg. We hereby designed this protocol based on the influence of thermal processing in the presence or absence of wheat on egg proteins, as investigated by ELISA, SDS-PAGE, and immunoblotting. At inclusion, children either passed an in-hospital cake challenge or had ovomucoid sIgE ≤1.2 kUA/L, which was considered safe for introduction at home.

Results

Gel electrophoresis revealed that the ovalbumin band became weaker with heating, while the ovomucoid band remained stable. In accordance, the IgE-binding to ovalbumin decreased with extensive heating, as opposed to ovomucoid. However, heating in the presence of wheat led to a decreased IgE reactivity to ovomucoid. Of the 78 children in the intention-to-treat group, 39 were randomized to each arm. Fifty-eight children reached the raw egg tolerance endpoint, of which 80% were in the short arm and 69% in the long arm. Within the short arm, the median time to raw egg tolerance was 24 months (95% CI, 21–27 months) compared to 30 months (95% CI, 28–32 months) in the long arm (p = 0.005). No grade IV reactions or cases of eosinophilic esophagitis were observed. The short arm was considered to be non-inferior to the long arm.

Conclusion

Our gradual short arm protocol appears to be safe and allows clinicians to guide baked egg tolerant children toward raw egg tolerance at home. The allergenicity of the egg proteins was affected by heating temperature and duration, as well as the presence of wheat.

Effects of salt and heat treatment on the physicochemical properties, microstructure, secondary structure, and simulated in vitro gastrointestinal digestion of duck egg white

BACKGROUND

The texture and structure of the duck egg white (DEW) gel under salt and heat treatment are crucial to its digestibility. Specifically, the structural changes of food protein gels have been recognized for their potential to regulate in vitro digestion. In this study, the effects of gel characteristics and simulated in vitro gastrointestinal digestion of DEW under combined salt and heat treatment were investigated.

RESULTS

With the increase in salting time and temperature, a porous opaque gel with large particles was formed, the moisture content of DEW showed a downward trend, and the same was true for hardness changes. The microstructure suggested that, with the penetration of NaCl, DEW proteins were denatured, and the protein molecules gradually unfolded and then aggregated after 7 days. The secondary structure revealed that, as the salting time and temperature increased, the proportion of intermolecular β-sheets and α-helices decreased. In terms of in vitro digestion, the highest digestibility was obtained at 14 days of salting combined with 100 °C heat treatment, and the digestibility was the lowest when marinated for 7 days at 121 °C. Liquid chromatography and tandem mass spectrometry (LC-MS/MS) indicated that the number of different types of peptides and specific peptides was positively correlated with the salting time and temperature of the DEW at the end of gastric digestion.

CONCLUSIONS

Heat treatment at 100 °C has a higher in vitro digestibility than at 121 °C. Gels with low hardness, large pores, and rough textures are easier to digest by pepsin and release more peptides. © 2021 Society of Chemical Industry.

Effect of processing technologies on the digestibility of egg proteins

Egg and egg products are a rich source of highly bioavailable animal proteins. Several processing technologies can affect the structural and functional properties of these proteins differently and can influence their fate inside the gastrointestinal tract. The present review examines some of the processing technologies for improving egg protein digestibility and discusses how different processing conditions affect the digestibility of egg proteins under gastrointestinal digestion environments. To provide up-to-date information, most of the studies included in this review have been published in the last 5 years on different aspects of egg protein digestibility. Digestibility of egg proteins can be improved by employing some processing technologies that are able to improve the susceptibility of egg proteins to gastrointestinal proteases. Processing technologies, such as pulsed electric field, high-pressure, and ultrasound, can induce conformational and microstructural changes that lead to unfolding of the polypeptides and expose active sites for further interactions. These changes can enhance the accessibility of digestive proteases to cleavage sites. Some of these technologies may inactivate some egg proteins that are enzyme inhibitors, such as trypsin inhibitors. The underlying mechanisms of how different technologies mediate the egg protein digestibility have been discussed in detail. The proteolysis patterns and digestibility of the processed egg proteins are not always predictable and depends on the processing conditions. Empirical input is required to tailor the optimization of processing conditions for favorable effects on protein digestibility.

The pattern of peptides released from dairy and egg proteins is highly dependent on the simulated digestion scenario

Evaluating the gastrointestinal (GI) fate of proteins is part of the assessment to determine whether proteins are safe to consume. In vitro digestion tests are often used for screening purposes in the evaluation of potential allergenicity. However, the current pepsin resistant test used by the European Food Safety Authority, only corresponds to fasted gastric conditions representative of a late phase adult stomach. In addition, these tests are performed on isolated proteins and the effect of the food matrix and processing are not systematically considered. The aim of this research is to compare three different static in vitro GI scenarios that are physiologically relevant. Namely, an infant, early phase (fed state) adult and late phase (fasted state) adult model. These protocols are applied to well-characterised isolated dairy (β-lactoglobulin and β-casein) and egg (lysozyme and ovalbumin) proteins and the impact of food matrix/processing on their proteolysis is also investigated. A combination of SDS-PAGE, LC-MS/MS and spectrophotometric assay was used for the evaluation of the proteolysis. Results highlight differences across the three GI scenarios whether on isolated proteins or within food matrices. The infant model led to incomplete digestion, leaving intact egg proteins, either isolated or in the food matrix, and intact β-lactoglobulin in the milk. In addition, peptides greater than 9 amino acids were found throughout the intestinal phase for all proteins studied, regardless of the scenario. This reinforces the difficulty of linking protein digestibility to potential allergenicity because many other factors are involved that need further investigation.

Impact of Cooking Preparation on In Vitro Digestion of Eggs Simulating Some Gastrointestinal Alterations in Elders

This study aimed to in vitro assess the impact of the cooking process of eggs (hard-boiled, poached, and omelet) on nutrients digestibility and vitamins A and D3 bioaccessibility under elderly gastrointestinal (GI) conditions. Three elderly digestion models were mimicked: oral (E1); oral and gastric (E2); and oral, gastric, and intestinal (E3), and a healthy adult model (C). Proteolysis extent reduced after digestion of omelet under the E3 model (p < 0.05) (up to 37% of reduction). Thus, hard-boiled and poached were more recommendable to enhance protein digestibility in elders. Altered GI conditions negatively influence neither the absorbable lipid fraction nor the cholesterol stability. Finally, vitamin A bioaccessibility was not affected but D3 slightly decreased with the elderly (E3). Hence, the digestion of nutrients was dependent on the resulting matrix, poached being the greater supplier of protein and lipid end-digestion products. Poached and omelet, however, offer a high net supply of bioaccessible vitamin D3 for elders.

Comparison of the edible quality of liquid egg with different cooking methods and their antioxidant activity after in vitro digestion

The purpose of this study was to compare the edible quality of liquid egg after steaming, baking, frying and microwaving. Texture profile analysis (TPA) and color analysis were used to evaluate the sensory characteristics of cooked eggs. The fat, vitamin A and E, protein and amino acid content of cooked eggs and the antioxidant activity after in vitro digestion were determined to display the variations in nutritional value. TPA results demonstrate that baked egg exhibited a softer and more elasticity texture, with a significant lower hardness of 3234 g than fried and microwaved eggs (p < 0.05). This is also consistent with the results of cohesiveness and chewiness. Consequences from scanning electron microscope showed plentiful honeycomb structure in baked egg, which may be related to the soft and elasticity texture. However, significantly higher contents of fat, vitamins A and E, protein were determined in fried egg (p < 0.05), which may be related to its lower moisture content. The strongest free radical scavenging efficiency for the hydroxyl, the DPPH and the superoxide radical were found in the gastrointestinal digestion of fried egg, with the rate of 95.76%, 81.08%, and 91.08%, respectively. Overall, baked egg showed superior soft and elasticity taste characteristics due to its honeycomb structure, while fried egg exhibited better antioxidant activity because of its high contents in vitamins and amino acids. The above results provide potential approach for the manufacture of pre-cooked eggs and related products using liquid eggs as ingredients.

Effect of pH and Heat Treatment on the Antioxidant Activity of Egg White Protein-Derived Peptides after Simulated In-Vitro Gastrointestinal Digestion

The study aimed to analyze pH and heat treatment’s effect in modulating the release of peptides with antioxidant activity after simulated gastrointestinal (GI) digestion of Egg white powder (EWP). EWP samples with neutral (EWPN) and alkaline (EWPA) pH were heat-treated at 20, 60, and 90 °C and analyzed for protein aggregation, solubility, and GI digestibility. Heat treatment decreased solubility and induced protein aggregation, which was higher for EWPN as compared to EWPA. The unfolding of EWPA proteins at 60 °C exhibited a higher GI digestibility and antioxidant activity via Oxygen Radical Absorbance Capacity (ORAC) assay as compared to EWPN. Interestingly, a reverse trend was observed in the cellular antioxidant assay, and the GI-digest of EWPN exhibited a higher antioxidant activity. The LC-MS/MS analysis are in concordance with cellular antioxidant activity assay and showed a higher intensity for peptides with potential antioxidant activity in the GI-digest of EWPN. The results indicate that heat treatment but not the pH is a critical factor in improving the protein digestibility and releasing peptides with antioxidant activity after GI digestion.

Modulation of gut microbiota in rats fed whole egg diets by processing duck egg to preserved egg

Pidan, as the preserved duck egg, is a traditional alkaline-pickled food in China. Previous studies have suggested preserved egg white has an anti-inflammatory effect, though the mechanism of action was unclear. In this work, the difference of peptides distribution in the digestive products was identified from those of duck egg. The effects of preserved egg diet on the modulation of gut microbiota as well as the alteration in fecal metabolites were further investigated. Minor variations of gut microbiota in phylum level were observed between preserved and fresh duck egg diet groups, even though, preserved egg diet intake attributed to increases in the relative abundance of Prevotella and Phascolarctobacterium (p < 0.05), while Ruminococcaceae and Allobaculum were quantitatively decreased (p < 0.05). In terms of metabolites, the contents of acetic acid (p < 0.01) and propionic acid (p < 0.05) were significantly increased in the preserved egg diet group. It was speculated that the preserved egg diet might alter the proportion of short-chain fatty acids (SCFAs) in the gut of rats by modulating specific intestinal bacteria, and subsequently play an active role in anti-inflammatory effects. Compared to the fresh egg group, the bacterial produced SCFAs of preserved egg group were increased in abundance (p < 0.05), which may have potential anti-obesity and anti-inflammatory effects. The results provide a novel insight into the relationship between preserved egg intake, gut microbiota and potential positive effects on host health.

A multi-approach peptidomic analysis of hen egg white reveals novel putative bioactive molecules

Chicken egg white is a raw material broadly used as additive for the preparation of food and cosmetoceutical products. To describe its molecular properties, various proteomic investigations were performed in the last decade characterizing highly abundant components. No peptidomic counterparts were accomplished so far; scientific literature only reports on the characterization of specific bioactive peptides or preparations from egg white and its hydrolysates, which was performed through dedicated functional assays. In this study, a broad description of the egg white peptidome at 24, 336 and 672 h after laying was achieved using three peptide extraction procedures, which were combined with MALDI-TOF-TOF-MS and nanoLC-ESI-Q-Orbitrap-MS/MS analyses. In the whole, 506 peptides were characterized; they mostly resulted from the physiological degradation of intact proteins following the activity of endoprotease ArgC-, trypsin- and plasmin-like enzymes. Eventual detection of peptide post-translational modifications also provided structural information on parental proteins. When analyzed by bioinformatics and/or compared with literature data, identified peptides allowed recognizing a number of protein fragments associated with different hypothetical biological activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics. Finally, a comparative label-free peptidomic evaluation of samples stored for different times under refrigeration identified 31 peptides showing significant quantitative changes during storage. BIOLOGICAL SIGNIFICANCE: This study provided the largest inventory of peptides described in chicken egg while so far. In addition, it identified a number of protein fragments associated with hypothetical antihypertensive, antioxidant, antiinflammatory, antimicrobial, anticancer, antiviral, antibiofilm, calcium-binding, antidiabetic, antithrombotic, adipogenic differentiating, stimulating/immunostimulating, hormonal, lipid-binding and cell adhesion-affecting activities. These results confirmed previous observations regarding functional characteristics of egg white unfractionated preparations or purified molecules, emphasizing the useful application of this raw material in human nutrition and cosmetics.

Effects of Starch on the Digestibility of Gluten under Different Thermal Processing Conditions

Gluten and starch are the primary ingredients of wheat. The complex reaction between gluten and starch will occur during thermal food processing, which will affect digestibility. The effects of proteins on the digestibility of starch have been reported, but the effects of starch on the digestibility of proteins have not been well-researched. In this paper, the effects of starch on gluten digestion during the heating process were studied by the gluten-starch simulated system, and it was found that starch can enhance gluten digestion. When the complex of 1:1 gluten-starch is heated at 100 °C, the digestibility of gluten is higher and more low-molecular-weight peptides are produced. Results from the digestibility and digestion peptide mapping of the gluten-starch complex at different conditions showed that the addition of starch during processing enhanced the digestion performance of gluten. Meanwhile, the secondary structure, intrinsic fluorescence, and microscopic structure of the gluten-starch complex were investigated to understand the mechanism of the enhancement. The digestion performance is related to the secondary structure variation during the thermal processing caused by the hydration increase and disulfide bond reduction. The gluten-starch complex spatial structure is looser than gluten after heating, which could expose more protease cleavage sites. These results suggest that starch can protect gluten from aggregation in water and destroy the spatial structure of gluten with the assistance of heating, exposing more cleavage sites and enhancing gluten digestion.

The Golden Egg: Nutritional Value, Bioactivities, and Emerging Benefits for Human Health

Egg is an encapsulated source of macro and micronutrients that meet all requirements to support embryonic development until hatching. The perfect balance and diversity in its nutrients along with its high digestibility and its affordable price has put the egg in the spotlight as a basic food for humans. However, egg still has to face many years of nutritionist recommendations aiming at restricting egg consumption to limit cardiovascular diseases incidence. Most experimental, clinical, and epidemiologic studies concluded that there was no evidence of a correlation between dietary cholesterol brought by eggs and an increase in plasma total-cholesterol. Egg remains a food product of high nutritional quality for adults including elderly people and children and is extensively consumed worldwide. In parallel, there is compelling evidence that egg also contains many and still-unexplored bioactive compounds, which may be of high interest in preventing/curing diseases. This review will give an overview of (1) the main nutritional characteristics of chicken egg, (2) emerging data related to egg bioactive compounds, and (3) some factors affecting egg composition including a comparison of nutritional value between eggs from various domestic species.