Effects of Maillard reaction on allergenicity of buckwheat allergen Fag t 3 during thermal processing

Quantifying allergenic proteins using antibody-based methods or liquid chromatography-mass spectrometry/mass spectrometry: A review about the influence of food matrix, extraction, and sample preparation

Accurate quantification of allergens in food is crucial for ensuring consumer safety. Pretreatment steps directly affect accuracy and efficiency of allergen quantification. We systematically reviewed the latest advances in pretreatment steps for antibody-based methods and liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) protein quantification methods in food. For antibody-based methods, the effects induced by food matrix like decreased allergen solubility, epitope masking, and nonspecific binding are of the upmost importance. To mitigate interference from the matrix, effective and proper extraction can be used to obtain the target allergens with a high protein concentration and necessary epitope exposure. Removal of interfering substances, extraction systems (buffers and additives), assistive technologies, and commercial kits were discussed. About LC-MS/MS quantification, the preparation of the target peptides is the crucial step that significantly affects the efficiency and results obtained from the MS detector. The advantages and limitations of each method for pre-purification, enzymatic digestion, and peptide desalting were compared. Additionally, the application characteristics of microfluidic-based pretreatment devices were illustrated to improve the convenience and efficiency of quantification. A promising research direction is the targeted development of pretreatment methods for complex food matrices, such as lipid-based and carbohydrate-based matrices.

Buckwheat Allergy in Asia

PURPOSE OF REVIEW

Buckwheat (BW) allergy is a significant issue in Asia. This review delves into three types of BW allergy: immediate food allergy; food-dependent, exercise-induced anaphylaxis (FDEIA) as a subset of immediate food allergy; and food protein-induced enterocolitis syndrome (FPIES); by comparing data from Asian and non-Asian countries.

RECENT FINDINGS

Most studies on BW have been published in Japan and Korea, and only a few studies on the topic have been done outside Asia. To date, seven components of common BW (Fagopyrum esculentum) and four components of Tartary BW (Fagopyrum tartaricum) have been implicated in BW allergy. Although BW-sIgE has limited utility for evaluating immediate BW allergy, Fag e 3-specific IgE, one of the components of common BW, and the skin prick test are diagnostically useful. The present review aims to shed light on the current state of knowledge, highlight research gaps, and suggest future directions in the management and understanding of BW allergy.

Dietary glycation compounds - implications for human health

The term "glycation compounds" comprises a wide range of structurally diverse compounds that are formed endogenously and in food via the Maillard reaction, a chemical reaction between reducing sugars and amino acids. Glycation compounds produced endogenously are considered to contribute to a range of diseases. This has led to the hypothesis that glycation compounds present in food may also cause adverse effects and thus pose a nutritional risk to human health. In this work, the Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) summarized data on formation, occurrence, exposure and toxicity of glycation compounds (Part A) and systematically assessed potential associations between dietary intake of defined glycation compounds and disease, including allergy, diabetes, cardiovascular and renal disease, gut/gastrotoxicity, brain/cognitive impairment and cancer (Part B). A systematic search in Pubmed (Medline), Scopus and Web of Science using a combination of keywords defining individual glycation compounds and relevant disease patterns linked to the subject area of food, nutrition and diet retrieved 253 original publications relevant to the research question. Of these, only 192 were found to comply with previously defined quality criteria and were thus considered suitable to assess potential health risks of dietary glycation compounds. For each adverse health effect considered in this assessment, however, only limited numbers of human, animal and in vitro studies were identified. While studies in humans were often limited due to small cohort size, short study duration, and confounders, experimental studies in animals that allow for controlled exposure to individual glycation compounds provided some evidence for impaired glucose tolerance, insulin resistance, cardiovascular effects and renal injury in response to oral exposure to dicarbonyl compounds, albeit at dose levels by far exceeding estimated human exposures. The overall database was generally inconsistent or inconclusive. Based on this systematic review, the SKLM concludes that there is at present no convincing evidence for a causal association between dietary intake of glycation compounds and adverse health effects.

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.

Effects of Different Amounts of Corn Silk Polysaccharide on the Structure and Function of Peanut Protein Isolate Glycosylation Products

Covalent complexes of peanut protein isolate (PPI) and corn silk polysaccharide (CSP) (PPI-CSP) were prepared using an ultrasonic-assisted moist heat method to improve the functional properties of peanut protein isolate. The properties of the complexes were affected by the level of corn silk polysaccharide. By increasing the polysaccharide addition, the grafting degree first increased, and then tended to be flat (the highest was 38.85%); the foaming, foam stability, and solubility were also significantly improved. In a neutral buffer, the solubility of the sample with a protein/polysaccharide ratio of 2:1 was 73.69%, which was 1.61 times higher than that of PPI. As compared with PPI, the complexes had higher thermal stability and lower surface hydrophobicity. High addition of CSP could made the secondary structure of PPI change from ordered α-helix to disordered β-sheet, β-turn, and random coil structure, and the complex conformation become more flexible and loose. The results of multiple light scattering showed that the composite solution exhibited high stability, which could be beneficial to industrial processing, storage, and transportation. Therefore, the functional properties of peanut protein isolate glycosylation products could be regulated by controlling the amount of polysaccharide added.

Bioactive compounds, health benefits, and industrial applications of Tartary buckwheat (Fagopyrum tataricum)

Tartary buckwheat belongs to the family Polygonaceae, which is a traditionally edible and medicinal plant. Due to its various bioactive compounds, the consumption of Tartary buckwheat is correlated to a wide range of health benefits, and increasing attention has been paid to its potential as a functional food. This review summarizes the main bioactive compounds and important bioactivities and health benefits of Tartary buckwheat, emphasizing its protective effects on metabolic diseases and relevant molecular mechanisms. Tartary buckwheat contains a wide range of bioactive compounds, such as flavonoids, phenolic acids, triterpenoids, phenylpropanoid glycosides, bioactive polysaccharides, and bioactive proteins and peptides, as well as D-chiro-inositol and its derivatives. Consumption of Tartary buckwheat and Tartary buckwheat-enriched products is linked to multiple health benefits, e.g., antioxidant, anti-inflammatory, antihyperlipidemic, anticancer, antidiabetic, antiobesity, antihypertensive, and hepatoprotective activities. Especially, clinical studies indicate that Tartary buckwheat exhibits remarkable antidiabetic activities. Various tartary buckwheat -based foods presenting major health benefits as fat and blood glucose-lowering agents have been commercialized. Additionally, to address the safety concerns, i.e., allergic reactions, heavy metal and mycotoxin contaminations, the quality control standards for Tartary buckwheat and its products should be drafted and completed in the future.

Limited Lactosylation of Beta-Lactoglobulin from Cow's Milk Exerts Strong Influence on Antigenicity and Degranulation of Mast Cells

Background: beta-lactoglobulin (BLG) is one of the major cow’s milk proteins and the most abundant allergen in whey. Heating is a common technologic treatment applied during milk transformational processes. Maillardation of BLG in the presence of reducing sugars and elevated temperatures may influence its antigenicity and allergenicity. Primary objective: to analyze and identify lactosylation sites by capillary electrophoresis mass spectrometry (CE-MS). Secondary objective: to assess the effect of lactosylated BLG on antigenicity and degranulation of mast cells. Methods: BLG was lactosylated at pH 7, a water activity (aw) of 0.43, and a temperature of 65 °C using a molar ratio BLG:lactose of 1:1 by incubating for 0, 3, 8, 16 or 24 h. For the determination of the effect on antibody-binding capacity of lactosylated BLG, an ELISA was performed. For the assessment of degranulation of the cell-line RBL-hεIa-2B12 transfected with the human α-chain, Fcε receptor type 1 (FcεRI) was used. Results: BLG showed saturated lactosylation between 8 and 16 incubation hours in our experimental setup. Initial stage lactosylation sites L1 (N-terminus)—K47, K60, K75, K77, K91, K138 and K141—have been identified using CE-MS. Lactosylated BLG showed a significant reduction of both the IgG binding (p = 0.0001) as well as degranulation of anti-BLG IgE-sensitized RBL-hεIa-2B12 cells (p < 0.0001). Conclusions and clinical relevance: this study shows that lactosylation of BLG decreases both the antigenicity and degranulation of mast cells and can therefore be a promising approach for reducing allergenicity of cow’s milk allergens provided that the process is well-controlled.

A Review on Epidemiological and Clinical Studies on Buckwheat Allergy

BACKGROUND

Cultivated buckwheat include two species originating from China: common buckwheat (Fagopyrum esculentum) and tartary buckwheat (Fagopyrum tartaricum). Buckwheat can cause IgE-mediated allergy, including severe allergic reactions and anaphylaxis. Exposure can occure when eating buckwheat food (food allergen), when producing or handling buckwheat food (occupational exposure) or when sleeping on buckwheat husk pillows (houeshold environmental exposure).

METHODS

A search on buckwheat allergy in the medical datbase PubMed from 1970-2020.

RESULT

A number of allergenic proteins have been identified in common buckwheat (e.g., Fag e 1, Fag e 2 and Fag e 3) and in tartary buckwheat (e.g., Fag t 1, Fag t 2, Fag t 3). Clinically relevant cross-reactivity has been described between buckwheat and peanut, latex, coconut, quinoa, and poppy seed. The prevalence of buckwheat allergy in the population can be estimated as 0.1-0.4% in Japan, Korea and buckwheat consuming areas of China. Among patients in allergy clinics in different countries, 2-7% has confirmed buckwheat allergy. School studies from Japan and Korea found 4-60 cases of buckwheat-related anaphylaxis per 100,000 school children. The incidence of severe allergic reactions to buckwheat, including anaphylaxis, can be estimated as 0.1-0.01 cases per 100,000 person-years.

CONCLUSIONS

Buckwheat allergy is a neglected allegy deserving further attention but severe allergic reactions are rare.

Investigation of glycated shrimp tropomyosin as a hypoallergen for potential immunotherapy

Tropomyosin (TM) is the most important allergen in shrimps that could cause food allergy. Glycation is reported to be effective in reducing TM allergenicity and produce hypoallergen; however, up to now, there are very few reports on the potential of hypoallergenic glycated TM (GTM) as allergen immunotherapy for shrimp TM-induced food allergy. This study investigated the glycation of TM-produced hypoallergen and the immunotherapeutic efficacy of GTM + Al(OH)₃ as potential allergen immunotherapy. Compared to TM, the TM glycated by glucose (TM-G), maltotriose (TM-MTS), maltopentaose (TM-MPS) and maltoheptaose (TM-MHS) had weaker allergy activation on mast cells and mouse model as a hypoallergen. However, the TM glycated by maltose (TM-M) insignificantly affected the allergenicity. In addition, the GTM absorbed into Al(OH)₃ could be efficacious as potential allergen immunotherapy, particularly for the TM glycated by the saccharides having larger molecular size (e.g., TM-MHS), which could provide preclinical data to develop GTM + Al(OH)₃ as a candidate immunotherapy for shrimp allergic patients.

Breeding Buckwheat for Increased Levels and Improved Quality of Protein

Tartary buckwheat (Fagopyrum tataricum (L.) Gaertn.) and common buckwheat (Fagopyrum esculentum Moench) are important sources of proteins with balanced amino-acid compositions, and thus of high nutritional value. The polyphenols naturally present in Tartary buckwheat and common buckwheat lower the true digestibility of the proteins. Digestion-resistant peptides are a vehicle for fecal excretion of steroids, and in this way, for bile acid elimination and reduction of cholesterol concentrations in serum. Buckwheat proteins are more effective compared to soy proteins for the prevention of gallstone formation. Tartary and common buckwheat grain that contains appropriate amounts of selenium-containing amino acids can be produced as functional food products. The protein-rich by-products of buckwheat are a good source of bioactive substances that can suppress colon carcinogenesis by reducing cell proliferation. The grain embryo is a rich source of proteins, so breeding buckwheat with larger embryos is a possible strategy to increase protein levels in Tartary and common buckwheat grain. However, chemical analysis of the grain is the most relevant criterion for assessing grain protein levels and quality.

Buckwheat proteins: functionality, safety, bioactivity, and prospects as alternative plant-based proteins in the food industry

The need for protein in human nutrition is rapidly increasing because of the increasing world population and consumer preference for high-protein foods. Plant proteins are gaining attention as sustainable means of meeting the global protein need due to their lower carbon footprint. Nonetheless, the food industry has neglected or underutilized many plant proteins, including buckwheat protein. Buckwheat is a pseudocereal and its groats contain beneficial components such as proteins, dietary fiber, vitamins, and bioactive polyphenols. The protein quality of buckwheat seeds varies between the tartary and common buckwheat types; both are gluten-free and contain considerable amount of indispensable amino acids. This review provides a detailed discussion on the profile, amino acid composition, digestibility, allergenicity, functional properties, and bioactivity of buckwheat proteins. Prospects of processing buckwheat for improving protein digestibility and deactivating allergenic epitopes were also discussed. Based on the literature, buckwheat protein has a tremendous potential for utilization in structuring food products and developing peptide-based functional foods for disease prevention. Future research should develop new processing technologies for further improvement of the quality and functional properties of buckwheat protein in order to facilitate its utilization as an alternative plant-based protein toward meeting the global protein supply.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

Effects of the Maillard Reaction on the Immunoreactivity of Amandin in Food Matrices

Amandin is the major storage protein and allergen in almond seeds. Foods, containing almonds, subjected to thermal processing typically experience Maillard browning reaction. The resulting destruction of amino groups, protein glycation, and/or denaturation may alter amandin immunoreactivity. Amandin immunoreactivity of variously processed almond containing foods was therefore the focus of the current investigation. Commercial and laboratory prepared foods, including those likely to have been subjected to Maillard browning, were objectively assessed by determining Hunter L^* , a^* , b^* values. The L^* values for the tested samples were in the range of 31.75 to 85.28 consistent with Maillard browning. Three murine monoclonal antibodies, 4C10, 4F10, and 2A3, were used to determine the immunoreactivity of the targeted samples using immunoassays (ELISA, Western blot, dot blot). The tested foods did not exhibit cross-reactivity indicating that the immunoassays were amandin specific. For sandwich ELISAs, ratio (R) of sample immunoreactivity to reference immunoreactivity was calculated. The ranges of R values were 0.67 to 15.19 (4C10), 1.00 to 11.83 (4F10), and 0.77 to 23.30 (2A3). The results of dot blot and Western blot were consistent with those of ELISAs. Results of these investigations demonstrate that amandin is a stable marker protein for almond detection regardless of the degree of amandin denaturation and/or destruction as a consequence of Maillard reaction encountered under the tested processing conditions.

PRACTICAL APPLICATION

Foods containing almond are often subjected to processing prior to consumption. Amandin, the major allergen in almond, may experience Maillard reaction. Understanding the change in amandin immunoreactivity as a result of Maillard reaction is important for amandin detection and production of hypoallergenic food products.

Maillard reaction in food allergy: Pros and cons

Food allergens have a notable potential to induce various health concerns in susceptible individuals. The majority of allergenic foods are usually subjected to thermal processing prior to their consumption. However, during thermal processing and long storage of foods, Maillard reaction (MR) often takes place. The MR is a non-enzymatic glycation reaction between the carbonyl group of reducing sugars and compounds having free amino groups. MR may sometimes be beneficial by damaging epitope of allergens and reducing allergenic potential, while exacerbation in allergic reactions may also occur due to changes in the motifs of epitopes or neoallergen generation. Apart from these modulations, non-enzymatic glycation can also modify the food protein(s) with various type of advance glycation end products (AGEs) such as Nϵ-(carboxymethyl-)lysine (CML), pentosidine, pyrraline, and methylglyoxal-H1 derived from MR. These Maillard products may act as immunogen by inducing the activation and proliferation of various immune cells. Literature is available to understand pathogenesis of glycation in the context of various diseases but there is hardly any review that can provide a thorough insight on the impact of glycation in food allergy. Therefore, present review explores the pathogenesis with special reference to food allergy caused by non-enzymatic glycation as well as AGEs.

Monoclonal Antibodies to Recombinant Fag e 3 Buckwheat Allergen and Development of a Two-site ELISA for Its Quantification

Purpose

Buckwheat is a major cause of anaphylaxis, and Fag e 3 is the key major allergen in buckwheat. However, an immunoassay system for the quantification of Fag e 3 has yet to be developed.

Methods

We developed a 2-site enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies (mAbs) produced against recombinant Fag e 3. We applied this ELISA to quantify native Fag e 3 in total buckwheat extract.

Results

Four clones of mAbs were produced, and all recognized vicilin allergens not only from buckwheat, but also from peanut and walnut. However, the ELISA using these antibodies was only able to quantify Fag e 3 in the total extract after addition of 1% sodium dodecyl sulphate (SDS) and heating, which facilitated dissociation of the allergen. The detection limit of the developed 2-site ELISA was 0.8 µg/mL. The measurement of Fag e 3 in the total extract of buckwheat showed that approximately 12% of protein in total buckwheat extract was Fag e 3.

Conclusions

We have developed an ELISA system for the quantification of the group 3 buckwheat allergen, Fag e 3, specifically. This assay will be useful for standardization of buckwheat allergens and monitoring of buckwheat contamination in foods.

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.

Chemical composition and health effects of Tartary buckwheat

Tartary buckwheat (Fagopyrum tataricum) contains a range of nutrients including bioactive carbohydrates and proteins, polyphenols, phytosterols, vitamins, carotenoids, and minerals. The unique composition of Tartary buckwheat contributes to their various health benefits such as anti-oxidative, anti-cancer, anti-hypertension, anti-diabetic, cholesterol-lowering, and cognition-improving. Compared with the more widely cultivated and utilised common buckwheat (F. esculentum), Tartary buckwheat tends to contain higher amounts of certain bioactive components such as rutin, therefore, showing higher efficiency in preventing/treating various disorders. This review summarises the current knowledge of the chemical composition of Tartary buckwheat, and their bio-functions as studied by both in vitro and in vivo models. Tartary buckwheat can be further developed as a sustainable crop for functional food production to improve human health.