Structural changes of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) treated shrimp tropomyosin decrease allergenicity

Glycation of β-Lactoglobulin with different lengths sugar chains: Impacts on structure, allergenicity and flavor profile

This study aims to perform a comparative study on the structure, allergenicity and flavor profile of β-lactoglobulin (BLG)-galacto-oligosaccharides, maltose, maltotriose and maltopentaose conjugates formed by glycation. Glycation increased BLG's molecular weight, altered the conformational structures and secondary structure from α-helix and β-sheet to β-turn and unordered forms. K47, K83, K91, K135, K138 and K141 of BLG were glycated, destructing the antigen epitopes, leading to reducing the IgE/IgG binding capacity and the release of histamine and interleukin-6 in KU812 cells, with BLG-galacto-oligosaccharides and BLG-maltose showed the lowest allergenicity. Meanwhile, 36 volatile organic compounds (VOCs) were identified in the conjugates, among which 11 were key VOCs, including 2,3-Butanedione and 2-propanol-M, which were the most abundant in BLG-galacto-oligosaccharides and BLG-maltose and positively correlated with glycation levels. Overall, glycation of proteins by different lengths sugar chains influenced the epitope structures and glycation levels, altering allergenicity and the release of flavor compounds.

Research Progress on Shrimp Allergens and Allergenicity Reduction Methods

Shrimp are highly favored by consumers for their delicious taste and rich nutritional value. However, reports of allergic reactions caused by shrimp and its derivatives have been increasing, significantly impacting consumer health and posing a growing global food safety concern. This article introduces the structure and biochemical characteristics of major allergenic proteins in shrimp, including tropomyosin (TM), arginine kinase, sarcoplasmic calcium-binding protein, myosin light chain, troponin C, and hemocyanin. Currently, there is no effective treatment for shrimp allergies, and prevention is mainly achieved by avoiding consumption. The study of shrimp allergen sensitization reduction technology is of great significance to the development of hypoallergenic or desensitized products. The article provides a detailed overview of the effects of common processing techniques, including physical, chemical, biological, and combined methods, on the allergenicity of shrimp allergens; for instance, the binding rate to immunoglobulin E (IgE) was reduced by 73.59% after treating TM with high pressure (500 MPa) at 55 °C for 10 min and the recognition rate of TM to IgE decreased by 89.4% on average after treating TM with pepsin (30 μg/mL, pH 2) for 2 h. These techniques provide references for the development of hypoallergenic aquatic products or desensitized foods.

Recent Advances of Processing and Detection Techniques on Crustacean Allergens: A Review

Crustaceans are delicious and highly nutritional food. However, crustaceans are one of the main food allergens, causing severe public health issues. Thus, it is important to increase the knowledge on crustacean allergens and protect the health of sensitized individuals. This review systematically summarizes the basic information on major crustacean allergens' characteristics, structures, and function. It also summarizes the latest evaluation and detection methods of crustacean allergens. In addition, various processing techniques to alleviate crustacean's allergenicity are discussed and compared. A host of multiplex approaches as innovative research is attractive to decrease crustacean allergenicity. In addition, the strategies to address the risk of crustacean allergens are also reviewed and discussed in detail. This review provides updates and new findings on crustacean allergens, which helps better understand crustacean allergy and provide novel strategies for its prevention and management.

Insight into the allergenicity and structure changes of parvalbumin from Trachinotus ovatus induced by dense-phase carbon dioxide

Parvalbumin (PV) is a major allergen in fish, and traditional treatments cannot reduce its sensitization. The effects of dense-phase carbon dioxide (DPCD) treatment on the sensitization and spatial structure of PV in Trachinotus ovatus were evaluated in this study. Western blotting and indirect ELISA were used to determine the allergenicity changes and spatial conformations of PV treated by DPCD. Tris-tricine-SDS-PAGE, circular dichroism, surface hydrophobicity, endogenous fluorescence, UV spectrophotometry, free amino group, total sulfhydryl group and SEM analyses were applied to characterize PV structure. The results showed that DPCD treatment (15 MPa, 30 min, 50 °C) could reduce PV-induced allergic reactions by 39-41 %, which destroyed the normal conformational epitopes and reduced the risk of PV-induced allergy. The secondary structure changed from ordered to disordered with a decreased content of α-helical groups, while the internal hydrophobic groups were exposed. The total sulfhydryl group content decreased significantly (P < 0.05). The surface hydrophobicity and ultraviolet absorption spectrum were enhanced, and the endogenous fluorescence peak shifted to a long wavelength. Meanwhile, the content of free amino groups increased significantly (P < 0.05). This study could provide a theoretical basis and a promising technical approach for reduction of PV allergenicities.

Genomics of Shrimp Allergens and Beyond

Allergy to shellfishes, including mollusks and crustaceans, is a growing health concern worldwide. Crustacean shellfish is one of the "Big Eight" allergens designated by the U.S. Food and Drug Administration and is the major cause of food-induced anaphylaxis. Shrimp is one of the most consumed crustaceans triggering immunoglobulin E (IgE)-mediated allergic reactions. Over the past decades, the allergen repertoire of shrimp has been unveiled based on conventional immunodetection methods. With the availability of genomic data for penaeid shrimp and other technological advancements like transcriptomic approaches, new shrimp allergens have been identified and directed new insights into their expression levels, cross-reactivity, and functional impact. In this review paper, we summarize the current knowledge on shrimp allergens, as well as allergens from other crustaceans and mollusks. Specific emphasis is put on the genomic information of the shrimp allergens, their protein characteristics, and cross-reactivity among shrimp and other organisms.

Mechanism of Cold Plasma Combined with Glycation in Altering IgE-Binding Capacity and Digestion Stability of Tropomyosin from Shrimp

Tropomyosin (TM) is a major crustacean allergen, and the present studies have tried to reduce its allergenicity by processing technologies. However, most research stopped on the allergenicity and structure of allergens, while information about epitopes was less. In this study, we first investigated the effects of cold plasma (CP) combined with glycation (CP-G) treatment on the processing and trypsin cleavage sites of TM from shrimp (Penaeus chinensis). The results showed a significant reduction in the IgE-binding capacity of TM after CP-G treatment, with a maximum reduction of 30%. This reduction was associated with the combined effects: modification induced by CP destroyed the core helical structure (D137 and E218) and occupied the potential glycation sites, leading to sequent glycation on conserved areas of TM, especially the epitope L130-Q147. Additionally, CP-G treatment decreased the digestion stability of TM by increasing the number of cleavage sites of trypsin and improving the efficiency of some sites, including K5, K6, K30, and R133, resulting in a lower IgE-binding capacity of digestion products, which fell to a maximum of 20%. Thus, CP-G is a valuable and reliable processing technology for the desensitization of aquatic products.

Modulating the allergenicity and functional properties of peanut protein by covalent conjugation with polyphenols

Peanut protein is a common food allergen. Our previous study demonstrated that the allergenicity of Ara h1 declines after covalent conjugation with polyphenols in vitro; however, how polyphenols affect the structure, function, and allergenicity of peanut protein extract (PPE) after covalent conjugating needs clarifying. Here, we assessed how the structure, function, and allergenicity of PPE changed after covalent conjugation with epigallocatechin-3-gallate (PPE-EGCG) and chlorogenic acid (PPE-CA). PPE covalently conjugated with EGCG and CA using the alkali treatment method. Multi-spectroscopy showed that the structure of PPE-EGCG/CA conjugate changed, becoming less folded. In contrast, the functional properties of PPE significantly improved. The allergenicity of PPE-EGCG/CA significantly declined in vitro and in vivo experiments. Our findings confirm that covalent conjugation of PPE with EGCG and CA reduces the allergenicity and improves the functional properties of PPE by changing the structure of the protein.

Insight into the conformational and allergenicity alterations of shrimp tropomyosin induced by Sargassum fusiforme polyphenol

Tropomyosin (TM) is the main allergen in shrimp food. Algae polyphenol reportedly could affect the structures and allergenicity of shrimp TM. In this study, the alterations of conformational structures and allergenicity of TM induced by Sargassum fusiforme polyphenol (SFP) were investigated. Compared to TM, the conjugation of SFP to TM induced conformational structure instability, the IgG-binding capacity and IgE-binding capacity of TM gradually decreased with more conjugation of SFP to TM, and the conjugation of SFP to TM could significantly reduce degranulation, histamine secretion and release of IL-4 and IL-13 from RBL-2H3 mast cells. Therefore, the conjugation of SFP to TM led to conformational instability, significantly decreased the IgG-binding capacity and IgE-binding capacity, weakened the allergic responses of TM-stimulated mast cell, and performed in vivo anti-allergic properties in BALB/c mouse model. Therefore, SFP could serve as candidate natural anti-allergic substances to reduce shrimp TM-induced food allergy.

Effects of methylglyoxal on shrimp tropomyosin structure and allergenicity during thermal processing

This study aimed to analyze the effect of methylglyoxal (MGO) on the structure and allergenicity of shrimp tropomyosin (TM) during thermal processing. The structural changes were determined by SDS-PAGE, intrinsic fluorescence, circular dichroism, and HPLC-MS/MS. The allergenicity was evaluated by in vitro and in vivo experiments. MGO could cause conformational structural changes in TM during thermal processing. Moreover, the Lys, Arg, Asp, and Gln residues of TM were modified by MGO, which could destroy and/or mask TM epitopes. In addition, TM-MGO samples could lead to lower mediators and cytokines released from RBL-2H3 cells. In vivo, TM-MGO caused a significant reduction in antibodies, histamine, and mast cell protease 1 levels in sera. These results indicate that MGO can modify the allergic epitopes and reduce the allergenicity of shrimp TM during thermal processing. The study will help to understand the changes in the allergenic properties of shrimp products during thermal processing.

Comprehensive Analysis of the Structure and Allergenicity Changes of Seafood Allergens Induced by Non-Thermal Processing: A Review

Seafood allergy, mainly induced by fish, shrimp, crab, and shellfish, is a food safety problem worldwide. The non-thermal processing technology provides a new method in reducing seafood allergenicity. Based on the structural and antigenic properties of allergenic proteins, this review introduces current methods for a comprehensive analysis of the allergenicity changes of seafood allergens induced by non-thermal processing. The IgE-binding capacities/immunoreactivity of seafood allergens are reduced by the loss of conformation during non-thermal processing. Concretely, the destruction of native structure includes degradation, aggregation, uncoiling, unfolding, folding, and exposure, leading to masking of the epitopes. Moreover, most studies rely on IgE-mediated assays to evaluate the allergenic potential of seafood protein. This is not convincing enough to assess the effect of novel food processing techniques. Thus, further studies must be conducted with functional assays, in vivo assays, animal trials, simulated digestion, and intestinal microflora to strengthen the evidence. It also enables us to better identify the effects of non-thermal processing treatment, which would help further analyze its mechanism.

Functional and Allergenic Properties Assessment of Conalbumin (Ovotransferrin) after Oxidation

Conalbumin (CA) is an iron-binding egg protein that has various bioactivities and causes major allergenicity in humans. This study investigated how oxidation affects the multiple functional properties of CA. The lipid peroxidation method was used to prepare treated CA [2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH)-CA and acrolein-CA] complexes. CA induced structural changes through oxidation. These changes enhanced the digestibility, rate of endocytosis in dendritic cells, and emulsifying and foaming properties of CA. ELISA and immunoblot analysis showed that the complexes reduced the IgE-binding ability of CA through lipid oxidation. KU812 cell assays showed that modification by AAPH and acrolein caused the release of IL-4 and histamine to decline. In conclusion, oxidation treatment modified the functional and structural properties of CA, reducing allergenicity during processing and preservation.

Two allergens from Scylla paramamosain share common epitopes showed different allergenic potential in Balb/c mice

Filamin C (FLN c) and triosephosphate isomerase (TIM) are novel allergens of crab (Scylla paramamosain) which are sharing common epitopes. This work aimed to assess their contributions to the induction and elicitation of allergenic responses. Balb/c mice were sensitized by intraperitoneal injections and challenged by intragastric gavage with purified proteins. Upon oral challenge, FLN c triggered more severe anaphylactic symptoms, higher levels of specific antibodies and histamine in serum than TIM, while TIM was a more active promotor of early specific antibody production and stimulated stronger Th2-biased responses. Combined with the results of in vitro assays, the data demonstrated that though with common epitopes, the two allergens showed a different allergenicity, TIM favored Th2 polarization in sensitization stage, while FLN c had a better ability to stimulate B cells and is highly immunogenic in oral challenge stage. The findings can help with the better understanding of allergenicity of crab allergens.

Effect of Peroxyl Radical-Induced Oxidation on Functional and Structural Characteristics of Walnut Protein Isolates Revealed by High-Resolution Mass Spectrometry

The present study aims to investigate the structural and functional properties of oxidated walnut protein isolates (WPI) by 2,2′-azobis (2-amidinopropane) dihydrochloride (AAPH). The oxidation degree, changes in structural characteristics, processing properties, and protein modifications of WPI were measured. The results showed that oxidation significantly induced structural changes, mainly reflected by the increasing carbonyl content, and decreasing sulfhydryl and free amino groups. Moreover, the secondary structure of WPI was altered in response to oxidation, and large aggregates formed through disulfide cross-linking and hydrophobic interactions. Almost all the property indicators were significantly decreased by oxidation except the foaming property and water/oil holding capacity. Mass spectrometry analysis showed that 16 different modifications occurred in amino acid side chains, and most of the protein groups with higher numbers of modifications were found to be associated with allergies, which was further confirmed by the reduction in antigenicity of the major allergen (Jug r 1) in WPI. Meanwhile, we used oxidation-related proteins for gene ontology (GO) enrichment analyses, and the results indicated that 115, 204 and 59 GO terms were enriched in terms of biological process, molecular function, and cellular component, respectively. In conclusion, oxidation altered the groups and conformation of WPI, which in turn caused modification in the functional properties correspondingly. These findings might provide a reference for processing and storage of walnut protein foods.

Effects of Superheated Steam Treatment on the Allergenicity and Structure of Chicken Egg Ovomucoid

The aim of this study was to explore the effects of an emerging and efficient heating technology, superheated steam (SS), on the allergenicity and molecular structure of ovomucoid (OVM). OVM was treated with 120–200 °C of SS for 2 to 10 min. The allergenicity (IgG/IgE binding abilities and cell degranulation assay) and molecular structure (main functional groups and amino acids modification) changes were investigated. The IgG-binding ability of OVM decreased and the releases of β-hex and TNF-γ were inhibited after SS treatment, indicating that the protein allergenicity was reduced. Significant increases in oxidation degree, free SH content and surface hydrophobicity were observed in SS-treated OVM. The protein dimer and trimer appeared after SS treatment. Meanwhile, obvious changes occurred in the primary structure. Specifically, serine can be readily modified by obtaining functional groups from other modification sites during SS treatment. Moreover, the natural OVM structure which showed resistance to trypsin digestion was disrupted, leading to increased protein digestibility. In conclusion, SS-induced OVM aggregation, functional groups and amino acids modifications as well as protein structure alteration led to reduced allergenicity and increased digestibility.

Mechanism of Reduction in Allergenicity and Altered Human Intestinal Microbiota of Digested β-Lactoglobulin Modified by Ultrasonic Pretreatment Combined with Glycation

The effects of ultrasound combined with glycation (UCG) on the allergenicity and human microbial community of β-Lg during in vitro digestion were studied by ELISA, cell experiments, and 16S rRNA high-throughput sequencing. UCG modification and subsequent digestion significantly reduced allergenicity. The decrease in the allergenicity of β-Lg depended not only on the low digestibility of glycated β-Lg, which led to the decrease of some peptides with complete immunogenicity, but also the masking effect of glycation on allergen epitopes of β-Lg. Meanwhile, UCG modification and subsequent digestion could alter the structures of intestinal microbiota and the community abundance at phylum, family, and genus levels, such as Bacteroidota, Fusobacteriota, Enterobacteriaceae, Bacteroidaceae, Ruminococcaceae, Bacteroides, and Faecalibacterium. These results show that simulated in vitro digestion of modified β-Lg reduces allergenicity and alters human intestinal microbiota, which could provide a theoretical basis for studying the relationship between intestinal dysbiosis and cow's milk allergy.

Effect of ultrasonic on the structure and quality characteristics of quinoa protein oxidation aggregates

Protein oxidation leads to covalent modification of structure and deterioration of functional properties of quinoa protein. The objective of this study was to investigate the effects of ultrasonic treatment on the functional and physicochemical properties of quinoa protein oxidation aggregates. In this concern, 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH) was selected as oxidative modification of quinoa protein. The microstructure of quinoa protein displayed by scanning electron microscope (SEM) indicated that oxidation induced extensive aggregation, leading to carbonylation and degradation of sulfhydryl groups. Aggregation induced by oxidation had a negative effect on the solubility, turbidity, emulsifying stability. However, according to the analysis of physicochemical properties, ultrasonic significantly improved the water solubility of quinoa protein. The quinoa protein treated by ultrasonic for 30 min exhibited the best dispersion stability in water, which corresponded to the highest ζ-potential, smallest particle size and most uniform distribution. Based on the FT-IR, SDS-PAGE and surface hydrophobicity analysis, the increase of α-helix, β-turn and surface hydrophobicity caused by cavitation effect appeared to be the main mechanism of quinoa protein solubilization. In addition, the hydrophobic region of the protein was re-buried by excessive ultrasonic treatment, and the protein molecules were reaggregated by disulfide bonds. Microstructural observations further confirmed that ultrasonic treatment effectively inhibited protein aggregation and improved the functional properties of quinoa protein.

Investigation into predominant peptide and potential allergenicity of ultrasonicated β-lactoglobulin digestion products

The effect of ultrasonicated β-lactoglobulin on the allergenic potential of predominant peptide was studied in vitro digestion. Gastrointestinal (GI) digestion of ultrasonicated β-lg was fractionated into four fractions, which have different molecular weight and allergenic potentials. The lowest allergenicity of fraction was produced by ultrasonicated β-Lg after GI digestion, depending on the changes in the structure of β-Lg by ultrasonic and the promotion of its proteolysis, resulting in the production of numerous small peptides with significantly reduced IgE activity and basophil histamine release. Mass spectrometry analysis showed that ultrasonic can promote the further hydrolysis of large intermediate peptides, Y42, L54, L57/L58, L95, L104/F105, L122 were target residues that became more available to protease by the pretreatment of ultrasonic, thus have a smaller molecular weight with reduced allergenic potential. Ultrasonic processing of milk products alone could reduce the risk of an allergenic reaction in milk allergy patients to some extent.

Dielectric-barrier discharge (DBD) plasma treatment reduces IgG binding capacity of β-lactoglobulin by inducing structural changes

The present study investigated the effects of dielectric-barrier-discharge (DBD) plasma treatment (12 kHz, 40 kV) at 1, 2, 3, and 4 min on the reduction of the immunoglobulin G (IgG) binding capacity of β-lactoglobulin (β-LG). The IgG binding capacity of β-LG was reduced by 58.21% following a plasma treatment time of 4 min, as confirmed by western-blot and ELISA analyses. The reduction in IgG binding capacity of β-LG was directly related to a stepwise change in its structure. The initial drop in the IgG binding capacity of β-LG was found to be caused by conformational alteration, free sulfhydryl exposure and cross-linkage of molecules induced by oxidation of NH-/NH₂- functional groups of peptide bonds and of sensitive amino acid residues (Tyr, Trp) as confirmed by SDS-PAGE, surface hydrophobicity and multi-spectroscopic analyses. Plasma treatment of more than 3 min resulted in cleavage of disulfidebonds and fragmentation of β-LG that was confirmed by LC-MS/MS analysis, which resulted a further decline in the IgG binding capacity of β-LG. Plasma treatment therefore has great potential as a substitute treatment for enzymatic hydrolysis for the production of hypoallergenic milk protein-based products.

Effect of MTGase on silver carp myofibrillar protein gelation behavior after peroxidation induced by peroxyl radicals

The objective of this study was to explore the oxidative modification induced by AAPH (2,2'-azobis (2-amidinopropane) dihydrochloride) on the microbial transglutaminase (MTGase) cross-linking reaction and gelling properties of silver carp myofibril protein (SCMP). Compared to AAPH treatment, MTGase addition resulted further changes of protein properties as evidenced by the decreasing free amino and thiol group content, the decreased secondary and tertiary structure, and the increasing storage modulus (G') and gel strength (P < 0.05). The proper oxidation induced by AAPH (5 mM) promoted the glutamine-lysine and disulfide cross-linking due to MTGase (10 U/g). Therefore, the quality of the SCMP gel was improved with a good water-holding capacity (WHC), gel strength and G'. This results could lay a theoretical foundation for the development of silver carp surimi products with good quality. Chemical compounds: (2,2'-azobis(2-amidinopropane)dihydrochloride (PubChem CID:76344); O-Phthalaldehyde (PubChem CID:4807); 5,5'-Dithiobis(2-Nitrobenzoic Acid) (PubChem CID:6254); 8-Anilino-1-naphthalenesulfonic acid (PubChem CID:1369); Acrylamide (PubChem CID: 6579); β-Mercaptoethanol (PubChem CID: 1567); Sodium dodecyl sulfate (PubChem CID:3423265).

Immunostimulatory and allergenic properties of emulsified and non-emulsified digestion products of parvalbumin (Scophthalmus maximus) in RBL-2H3 cells and BALB/c mouse models

In the present study, the influence of lipid emulsion on the allergenicity of digestion products of fish parvalbumin (PV) was investigated, which was initially subjected to simulated gastric/intestinal digestion both under emulsified and non-emulsified conditions. The release of β-hexosaminidase (β-hex), histamine (His), tryptase (TPS), interleukin 4 (IL-4), and IL-13 in RBL cells was decreased by 79.32, 26.19, 41.67, 53.95 and 54.40%, respectively, following stimulation with the gastric digestion products of PV. Whereas, lipid emulsified digestion products of PV (e-PV) significantly enhanced the release of active mediators and cytokines. The digestion products of emulsified PV at 180 min resulted in a higher release of β-hex (197.60%), His (12.18%), TPS (38.85%), IL-4 (48.19%) and IL-13 (59.40%), as compared to that of PV. However, no obvious differences in the release of active substances and cytokines were noted between intestinal digestion products of PV and intestinal digestion products of emulsified PV. In the mouse model studies, digested PV products reduced the anaphylactic scores, whereas e-PV manifested a higher level of allergic symptoms. Moreover, mice treated with 50% e-PV had significantly higher levels of specific IgE (32.56%), total IgE (16.67%) and total IgG1 (5.15%) than those treated with 50% PV. Mice treated with 50% e-PV had significantly higher levels of His (8.50%) and TPS (10.07%) compared with mice treated with 50% PV. Lipid emulsions altered the digestibility of PV in gastrointestinal digestion and enhanced the allergenicity of PV digestion products at the cellular levels, subsequently posing a higher risk of allergic reactions in susceptible individuals.

Comparison of digestibility and potential allergenicity of raw shrimp (Litopenaeus vannamei) extracts in static and dynamic digestion systems

In this work, a simplified dynamic digestion system was developed, and used for comparing the digestibility and potential allergenicity of raw shrimp extracts (RSE) in static and dynamic digestion systems. Protein hydrolysis was analyzed by electrophoresis, and the potential allergenicity was reflected in IgG/IgE binding ability and activation of basophils. In comparison with static digestion, protein hydrolysis indicated different kinetic behaviors, especially tropomyosin (TM) showed better digestion stability during dynamic digestion. The potential allergenicity of RSE exhibited different changing trends with digestion in the two systems. However, the apparent molecular weight (Mw) of immune fragments (>11 kDa) showed good approximation, and the IgE-binding fragment near 70 kDa revealed outstanding digestion stability than primordial protein in both systems. In conclusion, the dynamic conditions had a significant impact on the assessment of the persistence and potential allergenicity of digestion-resistant allergens, while the apparent Mw of IgG/IgE binding hydrolysate was not affected.

Azocompounds as generators of defined radical species: Contributions and challenges for free radical research

Peroxyl radicals participate in multiple processes involved in critical changes to cells, tissues, pharmacueticals and foods. Some of these reactions explain their association with degenerative pathologies, including cardiovascular and neurological diseases, as well as cancer development. Azocompounds, and particularly AAPH (2,2'-Azobis(2-methylpropionamidine) dihydrochloride), a cationic water-soluble derivative, have been employed extensively as sources of model peroxyl radicals. A considerable number of studies have reported mechanistic data on the oxidation of biologically-relevant targets, the scavenging activity of foods and natural products, and the reactions with, and responses of, cultured cells. However, despite the (supposed) experimental simplicity of using azocompounds, the chemistry of peroxyl radical production and subsequent reactions is complicated, and not always considered in sufficient depth when analyzing experimental data. The present work discusses the chemical aspects of azocompounds as generators of peroxyl (and other) radicals, together with their contribution to our understanding of biochemistry, pharmaceutical and food chemistry research. The evidence supporting a role for the formation of alkoxyl (RO•) and other radicals during thermal and photochemical decomposition of azocompounds is assessed, together with the potential influence of such species on the reactions under study.

Tyrosinase/caffeic acid cross-linking alleviated shrimp (Metapenaeus ensis) tropomyosin-induced allergic responses by modulating the Th1/Th2 immunobalance

In this study, the effect of enzymatic cross-linking of shrimp tropomyosin (TM) with tyrosinase and caffeic acid (TM-Tyr/CA) on the allergic response were assessed using in vitro and in vivo models. The RBL-2H3 and KU812 cell lines were employed to evaluate the changes in the stimulation abilities of TM-Tyr/CA that showed significant inhibition of mediators and cytokines. The digestibility of cross-linked TM was improved and the recognitions of IgG/IgE were markedly reduced, as revealed by western blotting. TM-Tyr/CA decreased anaphylactic symptoms, and hindered the levels of IgG1, IgE, histamine, tryptase and mouse mast-cell protease-1 (mMCP-1) in mice sera. Cross-linked TM downregulated the production of interleukin (IL)-4, IL-5, and IL-13 by 51.36, 12.24 and 20.55%, respectively, whereas, IL-10 and IFN-γ were upregulated by 20.71 and 19.0%. TM-Tyr/CA showed reduced allergenicity and may have preventive effect in relieving TM induced allergic response via immunosuppression and positive modulation of T-helper (Th)1/Th2 immunobalance.

Glycation of β-lactoglobulin combined by sonication pretreatment reduce its allergenic potential

β-lactoglobulin (β-Lg) was treated through different ultrasonic power and subsequently glycated with galactose to investigate its structural changes and immunological properties, and then evaluated by high-resolution mass spectrometry, enzyme-linked immunosorbent assay and basophil histamine release test. Ultrasonication combined with glycation (UCG) modification significantly reduced the IgE/IgG-binding capacity, and the release of β-hexosaminidase, histamine and interleukin-6, accompanied with changes in the secondary and tertiary structures. The decrease in the allergenicity of β-Lg depended not only on the glycation of K47, 60, 83, 91 and 135 within the linear epitopes, but also on the denaturation of conformational epitopes, which was supported by the glycation-induced alterations of the secondary and tertiary structures. This study confirmed that UCG modification is a promising method for decreasing the allergenic potential of allergic proteins, which is likely to develop a practical technology to produce hypo-allergenic milk.

Immunomodulatory Effect of Laccase/Caffeic Acid and Transglutaminase in Alleviating Shrimp Tropomyosin (Met e 1) Allergenicity

This work aimed to investigate the effect of enzymatic cross-linking on the allergenic potential of shrimp tropomyosin (TM), Met e 1. The cross-linked TM with laccase (CL), laccase/caffeic acid (CLC and CLC⁺), and transglutaminase (CTG and CTG⁺) formed macromolecules and altered the allergen conformation. The IgG/IgE-binding potentials of the cross-linked TM were reduced as confirmed by Western blotting and ELISA. Enzymatic cross-linking improved the gastrointestinal digestibility and induced a lower level of degranulation in RBL-2H3 and KU812 cells. Moreover, cross-linked TM decreased anaphylactic symptoms, as well as reduced the serum levels of IgG1, IgE, histamine, tryptase, and mMCP-1. In spleen cells, CLC⁺ and CTG⁺ downregulated the Th2-related cytokines and upregulated IFN-γ and IL-10. These findings revealed that CTG⁺ has shown more potential than CLC⁺ in mitigating the allergenicity of TM by influencing the conformational structure, enhancing the digestibility, decreasing the cellular degranulation process, and positively modulating the Th1/Th2 immunobalance.

Effect of tyrosinase and caffeic acid crosslinking of turbot parvalbumin on the digestibility, and release of mediators and cytokines from activated RBL-2H3 cells

Turbot can induce allergy in susceptible individuals due to the presence of parvalbumin (PV), a major fish allergen. This study aimed at evaluating the digestibility and the ability of PV to elicit the release of cellular degranulation, following treatment with tyrosinase (PV-Tyr), caffeic acid (PV-CA) and in combination (PV-Tyr/CA), using in vitro digestion and RBL-2H3 (passive rat basophil leukemia) cell line. The digestion assay products revealed that the stability of PV in simulated gastric fluid (SGF) was stronger, while in simulated intestinal fluid (SIF) was rather weak. Western blot analysis revealed that the IgG-binding abilities of the cross-linked PV were markedly reduced. Moreover, crosslinking hampered the release of cellular degranulation process in RBL-2H3 cell lines. PV-Tyr/CA showed highly significant reduction in the release rate of β-hexosaminidase (66.02%), histamine (35.01%), tryptase (29.25%), cysteinyl leukotrienes (29.72%), prostaglandin D₂ (34.96%), IL-4 (43.99%) and IL-13 (38.93%) and shown potential in developing hypoallergenic fish products.

Phosphorylation and Enzymatic Hydrolysis with Alcalase and Papain Effectively Reduce Allergic Reactions to Gliadins in Normal Mice

Gliadins are major allergens responsible for wheat allergies. Food processing is an effective strategy to reduce the allergenicity of gluten. In the present study, we determined the secondary and tertiary structures of gluten and gliadins treated by chemical, physical, and enzymatic means through FTIR, surface hydrophobicity, intrinsic fluorescence spectra, and UV absorption spectra. The results showed that the three treatments of phosphorylation and alcalase and papain hydrolyses significantly changed the conformational structures of gliadins, especially the secondary structure. Then, the potential allergenicity of the phosphorylated and alcalase and papain hydrolyzed gliadins were further characterized, and we observed a significant decrease in the allergenicity through the results of the index of spleen, serum total IgE, gliadin-specific IgE, histamine, and serum cytokine concentrations. An elevation of Th17 cells, the absence of Treg cells, and an imbalance in Treg/Th17 are associated with allergy. On the basis of the expression levels of related cytokines and key transcription factors, we also confirmed that phosphorylation and alcalase and papain hydrolysis could effectively reduce the allergenicity of gliadins by improving the imbalance of both Th1/Th2 and Treg/Th17 in the spleens of sensitized mice. This study suggested that the changes in conformational structure contribute to gliadin hyposensitization and that phosphorylation and alcalase and papain hydrolysis may be promising strategies for the production of wheat products with low allergenicity.