Comparison of the changes of the antigenicities of a hen's egg albumin by a gamma and an electron beam irradiation

Variation in the Allergenicity of Scrambled, Boiled, Short-Baked and Long-Baked Egg White Proteins

BACKGROUND

Hen's egg white (HEW) is the most common cause of food allergy in children which induces mild to fatal reactions. The consultation for a proper restriction is important in HEW allergy. We aimed to identify the changes in HEW allergenicity using diverse cooking methods commonly used in Korean dishes.

METHODS

Crude extract of raw and 4 types of cooked HEW extracts were produced and used for sodium dodecyl-sulfate polyacrylamide gel electrophoresis (SDS-PAGE), enzyme-linked immunosorbent assay (ELISA), and ELISA inhibition assays using 45 serum samples from HEW allergic and tolerant children. Extracts were prepared; scrambled without oil for 20-30 seconds in frying pan without oil, boiled at 100°C for 15 minutes, short-baked at 180°C for 20 minutes, and long-baked at 45°C for 12 hours with a gradual increase in temperature up to 110°C for additional 12 hours, respectively.

RESULTS

In SDS-PAGE, the intensity of bands of 50-54 kDa decreased by boiling and baking. All bands almost disappeared in long-baked eggs. The intensity of the ovalbumin (OVA) immunoglobulin E (IgE) bands did not change after scrambling; however, an evident decrease was observed in boiled egg white (EW). In contrast, ovomucoid (OM) IgE bands were darker and wider after scrambling and boiling. The IgE binding reactivity to all EW allergens were weakened in short-baked EW and considerably diminished in long-baked EW. In individual ELISA analysis using OVA+OM+ serum samples, the median of specific IgE optical density values was 0.435 in raw EW, 0.476 in scrambled EW, and 0.487 in boiled EW. Conversely, it was significantly decreased in short-baked (0.406) and long-baked EW (0.012). Significant inhibition was observed by four inhibitors such as raw, scrambled, boiled and short-baked HEW, but there was no significant inhibition by long-baked HEW (IC50 > 100 mg/mL).

CONCLUSION

We identified minimally reduced allergenicity in scrambled EW and extensively decreased allergenicity in long-baked EW comparing to boiled and short-baked EW as well as raw EW. By applying the results of this study, we would be able to provide safer dietary guidence with higher quality to egg allergic children.

Research advance of non-thermal processing technologies on ovalbumin properties: The gelation, foaming, emulsification, allergenicity, immunoregulation and its delivery system application

Ovalbumin (OVA) is the most abundant protein in egg white, with excellent functional properties (e.g., gelling, foaming, emulsifying properties). Nevertheless, OVA has strong allergenicity, which is usually mediated by specific IgE thus results in gut microbiota dysbiosis and causes atopic dermatitis, asthma, and other inflammation actions. Processing technologies and the interactions with other active ingredients can influence the functional properties and allergic epitopes of OVA. This review focuses on the non-thermal processing technologies effects on the functional properties and allergenicity of OVA. Moreover, the research advance about immunomodulatory mechanisms of OVA-mediated food allergy and the role of gut microbiota in OVA allergy was summarized. Finally, the interactions between OVA and active ingredients (such as polyphenols and polysaccharides) and OVA-based delivery systems construction are summarized. Compared with traditional thermal processing technologies, novel non-thermal processing techniques have less damage to OVA nutritional value, which also improve OVA properties. OVA can interact with various active ingredients by covalent and non-covalent interactions during processing, which can alter the structure or allergic epitopes to affect OVA/active components properties. The interactions can promote OVA-based delivery systems construction, such as emulsions, hydrogels, microencapsulation, nanoparticles to encapsulate bioactive components and monitor freshness for improving foods quality and safety.

Food irradiation: a promising technology to produce hypoallergenic food with high quality

The increasing incidence of food allergy cases is a public health problem of global concern. Producing hypoallergenic foods with high quality, low cost, and eco-friendly is a new trend for the food industry in the coming decades. Food irradiation, a non-thermal food processing technology, is a powerful tool to reduce the allergenicity with the above advantages. This review presents a summary of recent studies about food irradiation to reduce the allergenicity of food, including shellfish, soy, peanut, milk, tree nut, egg, wheat and fish. Principles of food irradiation, including mechanisms of allergenicity-reduction, irradiation types and characteristics, are discussed. Specific effects of food irradiation are also evaluated, involving microbial decontamination, improvement or preservation of nutritional value, harmful substances reduction of food products. Furthermore, the advantages, disadvantages and limitations of food irradiation are analyzed. It is concluded that food irradiation is a safety tool to reduce the allergenicity of food effectively, with high nutritional value and long shelf-life, making it a competitive alternative technology to traditional techniques such as heating treatments. Of note, a combination of irradiation with additional processing may be a trend for food irradiation.

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).

The Mechanism of Decreased IgG/IgE-Binding of Ovalbumin by Preheating Treatment Combined with Glycation Identified by Liquid Chromatography and High-Resolution Mass Spectrometry

Ovalbumin is one of the most important sensitizing ingredients in allergens of egg albumin, which restricts the application of egg in the field of food processing. Previous research has indicated that glycation could cause the protein to partially expand, which may bring about the destruction of the structural IgG and IgE epitopes and induce the decline of the IgG- and IgE-binding ability of ovalbumin. In this research, the effect of a preheating treatment integrated with glycation on the IgG- and IgE-binding capability and the conformation changes of ovalbumin was studied by detecting the glycated sites and the values of degree of substitution per peptide (DSP) by liquid chromatography and high-resolution mass spectrometry (LC-HRMS). Interestingly, we found that a glycation site (K227) attached by two ribose molecules was detected in glycated ovalbumin with preheating treatment. In addition, a new glycation site (K323) appeared in G-60. The results displayed that preheating treament could strengthen the changes in the secondary and tertiary structure of ovalbumin by enhancing glycation and further reduce the IgG/IgE-binding ability by integrating with glycation because of the cover of IgG and IgE epitopes. Therefore, preheating treatment integrated with glycation may offer a way for ovalbumin to reduce sensitization.

Glycation of ovalbumin after high-intensity ultrasound pretreatment: effects on conformation, immunoglobulin (Ig)G/IgE binding ability and antioxidant activity

BACKGROUND

Ovalbumin (OVA), a protein with excellent nutritional and processing properties, is the major allergen of hen egg white. High-intensity ultrasound treatment increases the immunoglobulin (Ig)G and IgE binding abilities by unfolding the conformational structure of OVA. This may allow a modification of the IgG and IgE binding of OVA by combining high-intensity ultrasound with other methods, such as glycation, thus representing a promising method for the improvement of protein properties.

RESULTS

Glycation with mannose (M) after ultrasound pretreatment at 0-600 W significantly reduced the IgG and IgE binding abilities and dramatically enhanced the antioxidant activity of OVA-M conjugates, with the lowest values of IgG and IgE binding and highest values of antioxidant capacity observed at 600 W. Polyacrylamide gel electrophoresis showed that the molecular weight of OVA-M conjugates with ultrasound pretreatment increased more than non-pretreatment sample, implying that ultrasound pretreatment promoted glycation. The α-helix content and ultraviolet absorption of OVA were observably increased, whereas β-sheet content, intrinsic fluorescence and surface hydrophobicity were notably decreased, indicating that the tertiary and secondary structures of OVA were markedly changed.

CONCLUSION

High-intensity ultrasound pretreatment can be conducive to reducing the binding abilities of IgG and IgE and enhancing the antioxidant activity of OVA-M conjugates. Therefore, glycation combined with high-intensity ultrasound pretreatment might be a promising method for producing hypo-allergenic and high-antioxidant OVA products. © 2018 Society of Chemical Industry.

High-intensity ultrasound enhances the immunoglobulin (Ig)G and IgE binding of ovalbumin

BACKGROUND

Hen eggs are widely used in food industry as a result of their excellent nutritional and processing properties and ovalbumin (OVA) is the major allergen of hen egg whites. Ultrasound has been widely used in the food processing industry, although the effect of high-intensity ultrasound on the immunoglobulin (Ig)G binding, IgE binding and conformational structure of OVA remains unclear.

RESULTS

Ultrasound treatment at 600-800 W dramatically increased the IgG and IgE binding of OVA, with the highest values observed at 600 W. The free sulfhydryl content, surface hydrophobicity and ultraviolet absorption were gradually increased when the power was increased from 200 to 600 W, implying the occurrence of molecule unfolding. When the power was 800 W, the binding ability was slightly decreased and was associated with the aggregation of OVA molecules. Polyacrylamide gel electrophoresis analysis implied that ultrasound treatment at 800 W could induce the aggregation of OVA molecules via disulfide bonds and/or hydrophobic interactions.

CONCLUSION

High-intensity ultrasound can increase the potential allergenicity of OVA. Therefore, high-intensity ultrasound processing of some egg products alone may improve the risk of an allergenic reaction in egg allergy patients to some extent. © 2016 Society of Chemical Industry.

Food Allergy

Food allergy is receiving increased attention in recent years. Because there is currently no known cure for food allergy, avoiding the offending food is the best defense for sensitive individuals. Type I food allergy is mediated by food proteins, and thus, theoretically, any food protein is a potential allergen. Variability of an individual's immune system further complicates attempts to understand allergen-antibody interaction. In this article, we briefly review food allergy occurrence, prevalence, mechanisms, and detection. Efforts aimed at reducing/eliminating allergens through food processing are discussed. Future research needs are addressed.

Food processing and allergenicity

Food processing can have many beneficial effects. However, processing may also alter the allergenic properties of food proteins. A wide variety of processing methods is available and their use depends largely on the food to be processed. In this review the impact of processing (heat and non-heat treatment) on the allergenic potential of proteins, and on the antigenic (IgG-binding) and allergenic (IgE-binding) properties of proteins has been considered. A variety of allergenic foods (peanuts, tree nuts, cows' milk, hens' eggs, soy, wheat and mustard) have been reviewed. The overall conclusion drawn is that processing does not completely abolish the allergenic potential of allergens. Currently, only fermentation and hydrolysis may have potential to reduce allergenicity to such an extent that symptoms will not be elicited, while other methods might be promising but need more data. Literature on the effect of processing on allergenic potential and the ability to induce sensitisation is scarce. This is an important issue since processing may impact on the ability of proteins to cause the acquisition of allergic sensitisation, and the subject should be a focus of future research. Also, there remains a need to develop robust and integrated methods for the risk assessment of food allergenicity.