A comprehensive review on glycation and its potential application to reduce food allergenicity.

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

Effect of tyrosinase-catalyzed crosslinking on the structure and allergenicity of turbot parvalbumin mediated by caffeic acid.

BACKGROUND: Enzymatic treatment of allergenic protein can alter their functional properties under a mild reaction condition due to specificity of enzymes. Phenolic compounds act as mediators and enhance the crosslinking reactions. The study aimed to assess the changes in the structure and immunoglobulin G (IgG) binding capacity of turbot parvalbumin (PV) upon crosslinking with tyrosinase (Tyr) in the absence and presence of caffeic acid. RESULTS: Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed the appearance of higher molecular weight bands (24, 36 kDa) in the crosslinked PV. The secondary structure of crosslinked PV became loosened and disordered. The results of intrinsic fluorescence and ultraviolet absorption spectral analyses, as well as surface hydrophobicity and free amino group analyses also revealed structural changes. As observed by western blot analysis, the intensity of the PV bands reduced upon Tyr treatment, indicating reduced binding of specific IgG to PV. Moreover, the indirect ELISA (enzyme-linked immunosorbent assay) analysis confirmed that the IgG binding ability of crosslinked PV was reduced 34.94%. CONCLUSION: Enzymatic treatment mitigated the allergenicity of fish PV, which was closely related to the alterations in the conformational structure. This treatment showed potential for developing hypoallergenic fish products under mild reaction conditions. © 2019 Society of Chemical Industry.

Allergenicity of acrolein-treated shrimp tropomyosin evaluated using RBL-2H3 cell and mouse model.

BACKGROUND: Food processing effects can modify protein functional properties. However, protein was oxidized inevitably by lipid peroxidation during food processing. Acrolein, a primary by-product of lipid peroxidation, can modify the structural and functional properties of protein. The aim of the research was to analyze the effect of acrolein on allergenicity of TM, a major allergen in shrimp. RESULTS: The overall allergenic effects of acrolein-treated TM were evaluated using female BALB/c mice and a mediator-releasing RBL-2H3 cell line. Acrolein-treated TM significantly decreased TM-specific immunoglobulin E/G1 levels, and histamine and mMCP-1 release in mouse serum. Release of inflammatory mediators such as ß-hexosaminidase, histamine, cysteinyl leukotriene and prostaglandin D2 was clearly suppressed after acrolein treatment. CONCLUSION: These results indicate that acrolein-induced tropomyosin modification can decrease the allergenicity of TM. This reduction contributes to allergenic potential changes in shrimp during processing and preservation. © 2018 Society of Chemical Industry.

Determining the effect of malondialdehyde on the IgE-binding capacity of shrimp tropomyosin upon in vitro digestion.

BACKGROUND: Stability in simulated gastric fluids is considered an important parameter for the estimation of food allergenicity. Moreover, proteins in food are highly susceptible to lipid oxidation during processing and preservation. In this study, the change in the IgE-binding capacity of malondialdehyde (MDA)-treated shrimp tropomyosin (TM) following in vitro digestion was investigated by SDS-PAGE and western blot. RESULTS: Shrimp TM treated with different concentrations of MDA was slightly degraded and became increasingly resistant to pepsin digestion over time. While untreated TM was rapidly degraded, MDA-treated TM showed some resistance and was degraded by trypsin only after increasing the digestion time. Results of immunoblotting studies on IgE using sera from patients allergic to shrimp indicated that the IgE-binding capacity of TM and MDA (50 mmol L-1 )-treated TM decreased slightly after pepsin digestion and significantly decreased after trypsin digestion. CONCLUSION: The study indicated that the resistance of TM to degradation increased after oxidation. The treatment with proteases, especially trypsin, is quite effective in decreasing the IgG/IgE-binding capacity of shrimp TM. © 2017 Society of Chemical Industry.

The inhibition mechanism of PostbioYDFF-3 on quality deterioration of refrigerated grass carp fillets from the perspective of endogenous enzyme and microorganisms changes.

The protective mode of PostbioYDFF-3 (referred to as postbiotics) on the quality stability of refrigerated fillets was explored from the aspects of endogenous enzyme activity and the abundance of spoilage microorganisms. Compared to the control group, the samples soaked in postbiotics showed significant reductions in TVC, TVB-N and TBARS values by 39.6%, 58.6% and 25.5% on day 5, respectively. In addition, the color changes, biogenic amine accumulation and texture softening of the fish fillets soaked in postbiotics were effectively suppressed. Furthermore, the activity of endogenous enzyme activities was detected. The calpain activities were significantly inhibited (p < 0.05) after soaking in postbiotics, which declined by 23%. Meanwhile, high throughput sequencing analysis further indicated that the growth of spoilage microorganism such as Acinetobacter and Pseudomonas were suppressed. Overall, the PostbioYDFF-3 was suitable for preserving fish meat.

Orally administered selenium-containing α-D-1,6-glucan and α-D-1,6-glucan relief early cognitive deficit in APP/PS1 mice.

Alzheimer's disease (AD) is a complex, progressive and deadly disorder that exhibits various typical pathological characteristics. Till now no effective treatment has been found that can prevent or reverse AD. Here, the effects of 2 months of treatment with α-D-1,6-glucan (CPA) and selenium-containing α-D-1,6-glucan (Se-CPA) on early cognitive dysfunction and neuropathology were explored in the 3-month-old APP/PS1 transgenic mouse. The results of the Morris water maze and open-field test revealed that Se-CPA exerted more significant effects than CPA in improving cognitive function and depressive-like behavior by attenuating the oxidative stress, decreasing serum LPS level, downregulating the inflammation of astrocytes and microglia through inhibiting the activation of NLRP3 inflammasome, mitigating neuronal cells loss and improving synaptic plasticity. Moreover, Se-CPA exerted beneficial effects on reshaping gut microbiome by increasing the microbial α-diversity, enhancing the proportion of beneficial bacteria such as Akkermansia muciniphila and promoting the SCFAs concentration. These findings provide evidence that Se-CPA might be a potentially viable compound for AD prevention.

Reducing the allergenicity of tropomyosin in shrimp by covalent conjugation with quercetin and chlorogenic acid.

The study aimed to assay the allergenicity of shrimp tropomyosin (TM) following covalent conjugation with quercetin (QR) and chlorogenic acid (CA). The structure of the TM-polyphenol covalent conjugates was examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), circular dichroism (CD), fluorescence, differential scanning calorimetry (DSC), and Fourier Transform infrared spectroscopy (FTIR). Potential allergenicity was evaluated using in vitro and in vivo methods. The results showed that QR and CA induced structural changes in TM through aggregation. RBL-2H3 cell results showed that TM-QR and TM-CA covalent conjugates reduced the release of ß-hexosaminidase and histamine, respectively. In the mice model, TM-QR and TM-CA covalent conjugates reduced the level of IgE, IgG, IgG1, histamine, and mMCP-1 in sera. Furthermore, the allergenicity was reduced by suppressing Th2-related cytokines (IL-4, IL-5, IL-13) and promoting Th1-related cytokines (IFN-γ). These research findings demonstrate that the covalent binding of TM with QR and CA, modifies the allergenic epitopes of shrimp TM, thereby reducing its potential allergenicity. This approach holds practical applications in the production of low-allergenicity food within the food industry.

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.

A pattern-free paper enzyme biosensor for one-step detection of fish freshness indicator hypoxanthine with a microfluidic aggregation effect.

In this study, a paper-based enzyme biosensor for hypoxanthine (Hx) was developed, enabling visual and one-step fish freshness detection. Xanthine oxidase and horseradish peroxidase were immobilized on nitrocellulose membranes with 3,3',5,5'-tetramethylbenzidine to output the colour signal. Chitosan oligosaccharide lactate-modified nitrocellulose membranes entrapped the dual-enzyme system and exhibited excellent microfluidic aggregation effect. The developed enzyme biosensor produced a linear response of 0.01-0.16 mmolL-1 with a detection limit of 8.22 µmolL-1, and was selective for Hx with recoveries of 96.13-103.11 % for fish samples. These biosensors were attached directly to the surface of fish samples and the colour was revealed within 3 min. Colour signals can be judged by the naked-eye to distinguish between fresh and spoiled fish samples and analyzed by a smartphone for quantitative analysis. The biosensor shows great potential as a powerful pattern- and reagent-free device for on-site freshness evaluation of fish.

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.

The conformational structural change of ß-lactoglobulin via acrolein treatment reduced the allergenicity.

ß-lactoglobulin (BLG) is a major allergen of milk. Since lipid peroxidation such as acrolein commonly exists during milk processing, it is necessary to evaluate its influence on BLG structure and potential allergenicity. The structure of acrolein-treated BLG was detected using SDS-PAGE, fluorescence, ultraviolet spectrum (UV), circular dichroism (CD) and LC-MS-MS, and the potential allergenicity was assessed by in vitro and in vivo assays. Results showed that acrolein could cause structural changes by BLG aggregation, which decreased the IgE binding capacity. Further, the release of mediators and cytokines decreased with acrolein treatment in RBL-2H3 cells. Mice showed lower allergenicity by the levels of BLG-specific antibody and the release of histamine and mMCP-1. These results explained that acrolein-induced BLG aggregation could damage the allergic epitopes and decrease the allergenicity of BLG in milk. The study will provide a new aspect to explore the natural phenomenon of allergen changes during food processing.

Changes in structure and allergenicity of shrimp tropomyosin by dietary polyphenols treatment.

Here, the potential allergenicity of shrimp tropomyosin (TM) after conjugation with chlorogenic acid (CA) and (-)-epigallo-catechin 3-gallate (EGCG) was assessed. Conformational structures of TM-polyphenol complexes were detected using SDS-PAGE, circular dichroism (CD), and fluorescence. Potential allergenicity was assessed by immunological methods, a rat basophil leukemia cell model (RBL-2H3), and in vivo assays. Indirect ELISA showed that TM-polyphenol complexes caused a conformational change to TM structure, with decreased IgG/IgE binding capacity significantly fewer inflammatory mediators were released with EGCG-TM and CA-TM in a mediator-releasing RBL-2H3 cell line. Mice model showed low allergenicity to serum levels of TM-specific antibody and T-cell cytokine production. EGCG-TM and CA-TM might reduce the potential allergenicity of shrimp TM, which could be used to produce hypoallergenic food in the food industry.

Reducing the Allergenicity of α-Lactalbumin after Lipid Peroxidation.

This study analyzed the effect of lipid peroxidation using 2,2'-azobis(2-amidinopropane)dihydrochloride (AAPH) and acrolein on the in vitro and in vivo allergenicity of α-lactalbumin (α-La). The structure of oxidized α-La was evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, fluorescence spectroscopy, and circular dichroism, whereas the changes in the allergenic properties were evaluated. Lipid peroxidation induced changes to the structural properties that might destroy and/or mask α-La epitopes. In comparison to native α-La, oxidation complexes caused a decrease in the immunoglobulin E (IgE) binding capacity, as observed via immunoblotting. Moreover, the capacity to release mediators and cytokines from KU812 cells was also greatly reduced. In vivo, oxidation with AAPH and acrolein caused a significant reduction in IgE, IgG, IgG1, mast cell protease 1, and plasma histamine, along with the reduction of mast surface c-Kit+ and FcεRI+ expression. Therefore, these results indicate that oxidation via AAPH and acrolein can potentially reduce the allergenicity of α-La, which can help with the better understanding of the changes in allergenicity of milk allergen by lipid peroxidation.

Lipid emulsion enhances fish allergen parvalbumin's resistance to in vitro digestion and IgG/IgE binding capacity.

This study was performed to determine Parvalbumin (PV), a well-known fish allergenic protein, digestion kinetics and immunoreactivity of digestion products with Immunoglobulin G/Immunoglobulin E recognition to understand its allergic potential with or without lipid emulsion process. PV was subjected to simulated gastrointestinal digestion in emulsified condition. Digestion kinetics of the protein was analysed by electrophoresis, IgG/IgE binding ability by immunoblotting and indirect ELISA. Lipid emulsion significantly (p < 0.01) reduced the degree of PV hydrolysis by 52.10% for gastric digestion. Immune fragments of gastric digestion were detectable for 90-120 min longer in emulsified condition showing resistance. Consequently, lipid emulsion decreased the digestive ability of PV in stomach, increasing resistance to gastrointestinal digestion by pepsin proteases. It also altered IgG/IgE binding ability of digestion products, thereby indicating that PV with lipid emulsion was resistant to digestion and possessed increased IgE binding ability resulting in higher risk of allergy among sensitized individuals.

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

The aim of this study was to analyze the effect of AAPH on the conformational structure and allergenicity of shrimp tropomyosin (TM). The structure of AAPH-TM was evaluated by SDS-PAGE, fluorescence, circular dichroism (CD) and ultraviolet light (UV), and the allergenicity was evaluated by in vivo and in vitro methods. Results showed that AAPH can induce structural changes through TM aggregations. These aggregations can decrease the IgG/IgE binding capacity on immunoblot analysis. Further competitive inhibition ELISA (ciELISA) results showed the IC50 of AAPH-TM (AAPH 0-25 mmol/l) changed from 0.086 to 46.2 µg/ml, which correlated with TM structural changes. An RBL-2H3 cell assay showed that release rate of ß-hexosaminidase and histamine decreased by 51.6% and 68.1% with AAPH (5 mmol/l) treatment, respectively. A mouse model showed AAPH-TM could decrease levels of IgE/IgG1, release of histamine and mMCP-1 in sera. In conclusion, AAPH induced TM aggregation can cause structural changes and decrease the allergenicity.

Effect of laccase-catalyzed cross-linking on the structure and allergenicity of Paralichthys olivaceus parvalbumin mediated by propyl gallate.

The aim of the present study was to evaluate Paralichthys olivaceus parvalbumin (PV) following treatment by laccase (LAC) in the presence of propyl gallate (PG) on the structure and potential allergenicity. The structure of LAC + PG treated PV was analyzed through SDS-PAGE, CD, fluorescence, and allergenicity was analyzed by immunological and cell model. Our results showed that LAC + PG treatment can induce structural changes through PV cross-linking. Western blotting and indirect ELISA analysis revealed the decrease in IgG binding capacity of PV, corresponding with the structural changes. The results of in vitro digestion illustrate that LAC + PG treated PV showed more resistance to gastrointestinal digestion compared to untreated PV. The release rate of ß-hexosaminidase and histamine decreased by 35.6% and 66.9%, respectively, with LAC + PG treatment by RBL-2H3 cell assay. Considering the wide utilization of LAC in food industry, our treatment reveals its potential for creation of hypoallergenic fish products under mild reaction conditions.

Effect of tyrosinase-aided crosslinking on the IgE binding potential and conformational structure of shrimp (Metapenaeus ensis) tropomyosin.

The present study was performed to determine crosslinking and oxidative reactions catalyzed by tyrosinase (Tyr), caffeic acid (CA) and their combination with respect to IgE binding potential and conformational structure of shrimp tropomyosin (TM). Cross-links and IgE binding potentials were analyzed by SDS-PAGE, western blot and indirect ELISA. While structural changes were characterized using surface hydrophobicity, ultraviolet (UV), fluorescence and circular dichroism (CD) spectroscopies. Maximum reduction in the IgG (37.19%) and IgE binding potentials (49.41%) were observed when treated with 2000 nkat/g Tyr + CA, as indicated by ELISA analyses. These findings correlated well with the denaturation of protein, as evident by slight blue shift and alterations in the ellipticities observed via structural analyses. The results demonstrated that addition of CA mediator with Tyr pronouncedly enhanced crosslinking, and altered the conformational structure, thereby mitigated allergenicity of TM, thus showing promise in developing novel food structures with reduced allergenic potential.

Inhibition of advanced glycation endproducts during fish sausage preparation by transglutaminase and chitosan oligosaccharides induced enzymatic glycosylation.

Advanced glycation endproducts (AGEs) are the harmful products of non-enzymatic reactions in foods formed during the heating process. In order to reduce the content of AGEs in foods, the inhibitory effect of different proportions of transglutaminase (TGase) and chitosan oligosaccharides (COS) on the AGEs of seabream fish meat sausage was studied. The results indicated that the TGase/COS ratio of 1 : 1 could inhibit the formation of AGEs, showing especially a decreased Nε-carboxymethyl-lysine (CML) content and a twice higher inhibition rate (36.4%) than that by aminoguanidine (17.4%), a commonly effective positive inhibitor of AGEs. The data of lysine, fructosamine, and glucosamine contents, combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analyses, demonstrated that cross-linking of proteins and glycosylation of glutamine induced by TGase and COS resulted in steric hindrance that inhibited glycation. These findings revealed that TGase catalyzed glycosylation with COS differently from general antioxidants had potential as an effective treatment to inhibit the formation of AGEs in fishery products.

Impacts of glycation and transglutaminase-catalyzed glycosylation with glucosamine on the conformational structure and allergenicity of bovine ß-lactoglobulin.

ß-Lactoglobulin (ß-LG) is recognized as the major milk allergen. In this study, the effects of transglutaminase (TGase) and glucosamine (GlcN)-catalyzed glycosylation and glycation on the conformational structure and allergenicity of ß-LG were investigated. The formations of cross-linked peptides were demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), and GlcN-conjugated modification was identified using matrix-assisted laser desorption ionization-time of flight-mass spectrometry (MALDI-TOF-MS). Structural analysis revealed that glycosylation and glycation of ß-LG induced unfolding of the primary protein structure followed by a loss of the secondary structure. As revealed by circular dichroism (CD) spectroscopy, glycosylated ß-LG exhibited the highest increase in the ß-sheets from 32.6% to 40.4% (25 °C) and 44.2% (37 °C), and the percentage of α-helices decreased from 17.7% to 14.4% (25 °C) and 12.3% (37 °C), respectively. The tertiary and quaternary structures of ß-LG also changed significantly during glycosylation and glycation, along with reduced free amino groups and variation in surface hydrophobicity. Immunoblotting and indirect enzyme-linked immuno sorbent assay (ELISA) analyses demonstrated that the lowest IgG- and IgE-binding capacities of ß-LG were obtained following glycosylation at 37 °C, which were 52.7% and 56.3% lower than that of the native protein, respectively. The reduction in the antigenicity and potential allergenicity of glycosylated ß-LG was more pronounced compared to TGase treated- and glycated ß-LG, which correlated well with the structural changes. These results suggest that TGase-catalyzed glycosylation has more potential compared to glycation for mitigating the allergenic potential of milk products.

Changes of structure and IgE binding capacity of shrimp (Metapenaeus ensis) tropomyosin followed by acrolein treatment.

Tropomyosin, a major allergen of shrimp, presents high stability to various conditions owing to the high content of α-helix. Chemical modification of tropomyosin can induce structural changes and affects IgE binding capacity. Since lipid peroxidant such as acrolein commonly exists during shrimp preservation, it is necessary to evaluate its influence on tropomyosin structure and IgE binding capacity. Western blot and inhibition enzyme-linked immunosorbent assay were used to illustrate IgE binding capacity, while structural changes were investigated by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and fluorescence spectroscopy. Results revealed that IgE binding capacity reduced and the secondary structure denatured following treatment with increasing concentration of acrolein. Furthermore, the identification of LC-MS/MS indicated that the free amines of lysine, tyrosine, and histidine residues were altered by acrolein. These amino acid modifications resulted in the collapse of epitopes, as well as structural changes responsible for the decreased IgE binding capacity of shrimp tropomyosin.