Advanced DNA- and Protein-based Methods for the Detection and Investigation of Food Allergens

Selection of signature peptide biomarkers for the sesame allergens in commercial food based on LC-MS/MS

Sesame is a commonly used food ingredient, yet it is one of the eight major allergens. As sesame is often consumed in various processed forms, it is important to establish methods for detecting sesame allergens in processed foods. Liquid chromatography-tandem mass spectrometry (LC-MS/MS), using characteristic peptides as biomarkers, detects multiple allergenic proteins simultaneously with high sensitivity and accuracy. Choosing robust biomarkers is beneficial for developing a specific, universal, and sensitive method. To obtain excellent peptides of sesame allergens, sixteen commercial products were used as test materials. Proteins from these materials were extracted, digested, and analyzed. Peptides were screened based on several criteria, including specificity and amino acid composition. Only peptides showing process robustness were retained. Ultimately, nine peptides were selected as the best biomarkers. Based on the above peptides, it is possible to achieve precise and high-sensitivity detection of sesame allergens in processed products.

M13 bacteriophage based fluorescence immunoassay against food allergens of Ara h 3 and Mac i 1

Food allergy is increasingly prevalent and poses notable health risks, which underscores the urgent need to develop reliable and sensitive detection methods for effective identification of food allergens. This study aims to address the limitations of existing methods by developing an immunoassay utilizing bacteriophage/carbon dots (CDs)@silica core-shell nanospheres. Two CDs with different emission wavelengths (513 nm for Green CDs, 645 nm for Red CDs) were synthesized for signal development and amplification. The nanobodies (Nbs) displayed on M13 bacteriophage were employed for the rapid fluorescence quantification of peanut allergen Ara h 3 and macadamia allergen Mac i 1 through magnetic separation. Generally, the method was established with detection limits of 9.5 and 10.2 ng/mL for Ara h 3 and Mac i 1, respectively, demonstrating a sensitivity of 2-5 times greater than traditional methods. Collectively, this multiplexed testing offers a potential analytical strategy based on bacteriophage for effective screening of food allergens.

Screening, identification, and application of aptamers against allergens in food matrices

Food allergies have become one of the most pressing issues in food safety and public health globally along with their incidence increasing in recent years. The reliable recognition of allergens from different sources, especially food-hidden allergens, is essential for preventing and controlling food allergies. Recently, aptamers, as emerging recognition elements, have gained considerable attention in food allergy, especially in the detection of food allergens. This review systematically summarizes the latest progress in screening, identification, and application of aptamers against food allergens over the past five years. We first introduce a brief overview of food allergy and aptamers, followed by a detailed focus on the aptamers' research against different food allergens broadly based on the major categories of the Big-8 allergens: highlighting the newly screened aptamers and their applied systematic evolution of ligands by exponential enrichment (SELEX) strategies, and emphasizing their practical applications including aptasensors, allergy inhibitors, or affinity adsorptions. Finally, the remaining challenges and future exploitations faced by aptamers in food allergens are comprehensively discussed and depicted. This review holds the promise of inspiring a broader range of researchers to gain an in-depth understanding of food allergy assisted by aptamer recognition and to facilitate improved biochemical analyses and successful application.

Voltammetric immunosensor based on oxidized carbon nanotubes/MnFe2O4 hybrid nanoplatform for amplified detection of celery (Apium graveolens)

Celery is a food allergen that must be included in the ingredient list of commercial food products in the European Union. This is a challenge for the food industry because of potential cross-contamination and undeclared ingredients because of their low concentrations. So, the food industry requires expedited high-performance analytical methods. The development, validation and application of a magnetic nanomaterial-based voltammetric immunosensor is reported to quantify a major celery allergen (Api g 1), achieving a low limit of detection (32 pg·mL-1, in a 40-μL sample). The applicability of the biosensor was evaluated by analysing twenty food products and the lowest Api g 1 content (1.1 ± 0.9 mg·kg-1) was quantified in a cooked sample. The selectivity of the method and the interference of similar fresh products (e.g., parsley, basil) were evaluated. This portable and easy-to-use biosensor can be a fit-for-purpose solution to tackle a major problem for the food industry.

Comparison of commercial DNA kits for allergen detection of celery in food matrices

For correct allergen risk management by industry, retail and food safety authorities, sensitive and reliable fast allergen detection methods are required, even more when precautionary allergen labelling based on reference doses will be implemented in legislation. This study aimed to perform a comparative assessment of three commercially available quantitative or qualitative test kits, for DNA analysis of celery in food products. Five product groups, representing different sectors of the AOAC food-matrix triangle, being (plant-based) meat products, snacks, sauces, dried herbs and spices, and smoothies, were identified to potentially contain celery. From each group, blank and incurred (labelled to contain celery) food products were selected, of which the blank food products were additionally spiked with low protein levels of celery prior to qPCR assessment. Results show that the assessed test kits perform according to their specifications, however, a clear influence of the matrix on the detection ability of celery was observed. In addition, quantification of the amount of celery in the different food products showed to be challenging in all food product groups using the two quantification kits.

Recent advance in sesame allergens: Influence of food processing and their detection methods

Sesame (Sesamum indicum L.) is a valuable oilseed crop with numerous nutritional benefits containing a diverse range of bioactive compounds. However, sesame is also considered an allergenic food that triggers various mild to severe adverse reactions (e.g., anaphylaxis). Strict dietary avoidance of sesame components is the best option to protect the sensitized consumers. Sesame or sesame-derived foods are always consumed after certain food processing operations, which would cause a considerable impact on the structure of sesame proteins, changing their sensitization capacity and detectability. In the review, the molecular structure properties, and immunological characteristics of the sesame allergens were described. Meanwhile, the influence of food processing techniques on sesame proteins and the relevant detection techniques used for the sesame allergens quantification are also emphasized critically. Hopefully, this review could provide valuable insight into the development and management for the new "Big Eight" sesame allergen in food industry.

Fluorescent polythymidine-templated copper nanoclusters aptasensor for sensitive detection of tropomyosin in processed shrimp products

Tropomyosin (TM) is the main allergen in shellfish. Developing a novel, simple and accurate method to track and detect TM in food products is necessary. In this work, a label-free fluorescent aptasensor based on polythymidine (poly(T))-templated copper nanoclusters (CuNCs) was designed for sensitive detection of TM in processed shrimp products. Magnetic beads (MBs), aptamer and cDNA were used to construct an MBs-aptamer@cDNA complex as a detection probe, and with the presence of TM, the poly(T)-templated CuNCs attached at the end of the cDNA as the fluorescent signal was released from the complex to turn on the fluorescence. Under optimal conditions, the poly(T)-templated CuNCs aptasensor achieved a linear range from 0.1 to 50 μg/mL (R2 = 0.9980), a low limit of detection of 0.0489 μg/mL and an excellent recovery percentage of 105.29%-108.91% in the complex food matrix, providing a new approach for food safety assurance.

Simultaneous Identification and Species Differentiation of Major Allergen Tropomyosin in Crustacean and Shellfish by Infrared Spectroscopic Chemometrics

To solve the lack of rapid and accurate methods for allergen identification and traceability, an infrared spectroscopic chemometric analytical model (IR-CAM) was established by combining infrared spectroscopy with principal component and cluster analysis. By comparing the second derivative infrared (SD-IR) spectra of 5 proteins and 14 crustaceans and shellfish tropomyosin (TM), 8 shared peaks and unique fingerprint peaks in the amide III region were found for crabs, shrimps, and shellfish. Based on the unique fingerprint peaks coexisting with shared peaks, allergen TM in crustaceans and shellfish could be identified within 10 min (cf. ELISA ∼ 4 h). Concurrently, the species differentiation of TM at the Class/Family level was achieved based on IR-CAM. Validation by fermented aquatic products TM (n = 60) demonstrated that the developed IR-CAM could simultaneously identify and differentiate TM in crustaceans and shellfish accurately. It could be applied for allergen detection and traceability of aquatic products on an antibody-free basis.

A portable smartphone-based imaging surface plasmon resonance biosensor for allergen detection in plant-based milks

Food allergies are hypersensitivity immune responses triggered by (traces of) allergenic compounds in foods and drinks. The recent trend towards plant-based and lactose-free diets has driven an increased consumption of plant-based milks (PBMs) with the risk of cross-contamination of various allergenic plant-based proteins during the food manufacturing process. Conventional allergen screening is usually performed in the laboratory, but portable biosensors for on-site screening of food allergens at the production site could improve quality control and food safety. Here, we developed a portable smartphone imaging surface plasmon resonance (iSPR) biosensor composed of a 3D-printed microfluidic SPR chip for the detection of total hazelnut protein (THP) in commercial PBMs and compared its instrumentation and analytical performance with a conventional benchtop SPR. The smartphone iSPR shows similar characteristic sensorgrams compared with the benchtop SPR and enables the detection of trace levels of THP in spiked PBMs with the lowest tested concentration of 0.625 μg/mL THP. The smartphone iSPR achieved LoDs of 0.53, 0.16, 0.14, 0.06, and 0.04 μg/mL THP in 10x-diluted soy, oat, rice, coconut, and almond PBMs, respectively, with good correlation with the conventional benchtop SPR system (R² 0.950-0.991). The portability and miniaturized characteristics of the smartphone iSPR biosensor platform make it promising for the future on-site detection of food allergens by food producers.

Iron/iron oxide-based magneto-electrochemical sensors/biosensors for ensuring food safety: recent progress and challenges in environmental protection

Foodborne diseases have arisen due to the globalization of industry and the increase in urban population, which has led to increased demand for food and has ultimately endangered the quality of food. Foodborne diseases have caused some of the most common public health problems and led to significant social and economic issues worldwide. Food quality and safety are affected by microbial contaminants, growth-promoting feed additives (β-agonists and antibiotics), food allergens, and toxins in different stages from harvesting to storage and marketing of products. Electrochemical biosensors, due to their reduced size and portability, low cost, and low consumption of reagents and samples, can quickly provide valuable quantitative and qualitative information about food contamination. In this regard, using nanomaterials can increase the sensitivity of the assessment. Magnetic nanoparticle (MNP)-based biosensors, especially, are receiving significant attention due to their low-cost production, physicochemical stability, biocompatibility, and eco-friendly catalytic characteristics, along with magnetic, biological, chemical and electronic sensing features. Here, we provide a review on the application of iron-based magnetic nanoparticles in the electrochemical sensing of food contamination. The types of nanomaterials used in order to improve the methods and increase the sensitivity of the methods have been discussed. Then, we stated the advantages and limitations of each method and tried to state the research gaps for each platform/method. Finally, the role of microfluidic and smartphone-based methods in the rapid detection of food contamination is stated. Then, various techniques like label-free and labelled regimes for the sensitive monitoring of food contamination were surveyed. Next, the critical role of antibody, aptamer, peptide, enzyme, DNA, cells and so on for the construction of specific bioreceptors for individual and simultaneous recognition by electrochemical methods for food contamination were discussed. Finally, integration of novel technologies such as microfluidic and smartphones for the identification of food contaminations were investigated. It is important to point out that, in the last part of each sub-section, attained results of different reports for each strategy were compared and advantages/limitations were mentioned.

First PCR-free electrochemical bioplatform for the detection of mustard Sin a 1 protein as a potential "hidden" food allergen

A disposable electrochemical PCR-free biosensor for the selective detection of a fragment encoding the protein Sin a 1, a 2S albumin considered a diagnostic marker for sensitization to mustard, is reported. The methodology is based on the formation of DNA/RNA heterohybrids by sandwich hybridization of a specific fragment of the Sin a 1 allergen coding sequence with appropriately designed RNA probes. Labeling with commercial antibodies specific to the heteroduplexes and secondary antibodies conjugated with horseradish peroxidase (HRP) was carried out onto the surface of magnetic beads (MBs). Amperometric transduction was undertaken on screen-printed electrodes using H₂O₂ as enzyme substrate and hydroquinone (HQ) a redox mediator. The electrochemical biosensor allows the simple and fast detection (75 min) of Sin a 1 reaching a limit of detection of 3 pM. The bioplatform was successfully applied to the analysis of the targeted Sin a 1 gene specific region using just 50 ng of non-fragmented denatured genomic DNA extracted from yellow mustard seeds.

Identification of Fish Species and Targeted Genetic Modifications Based on DNA Analysis: State of the Art

Food adulteration is one of the most serious problems regarding food safety and quality worldwide. Besides misleading consumers, it poses a considerable health risk associated with the potential non-labeled allergen content. Fish and fish products are one of the most expensive and widely traded commodities, which predisposes them to being adulterated. Among all fraud types, replacing high-quality or rare fish with a less valuable species predominates. Because fish differ in their allergen content, specifically the main one, parvalbumin, their replacement can endanger consumers. This underlines the need for reliable, robust control systems for fish species identification. Various methods may be used for the aforementioned purpose. DNA-based methods are favored due to the characteristics of the target molecule, DNA, which is heat resistant, and the fact that through its sequencing, several other traits, including the recognition of genetic modifications, can be determined. Thus, they are considered to be powerful tools for identifying cases of food fraud. In this review, the major DNA-based methods applicable for fish meat and product authentication and their commercial applications are discussed, the possibilities of detecting genetic modifications in fish are evaluated, and future trends are highlighted, emphasizing the need for comprehensive and regularly updated online database resources.

Detection of Fish Allergens in Foods Using an In-House Real-Time PCR Targeting the Ribosomal 18S rRNA Gene

Fish is one of the major food allergens which, in sensitised individuals, can cause life-threatening allergic reactions, even when present in small amounts. To protect consumers' health, the correct labeling of foods is important. The objective of the present study was to validate an in-house real-time PCR method targeting the ribosomal 18S rRNA gene as universal DNA marker for the detection of fish in foods. The specificity of the primers was assessed on 20 fish species commonly marketed in the Mediterranean basin and other species of molluscs and crustaceans and foods of animal and plant origin. The absolute detection of the method was assessed using DNA extracted from a fish mixture and the SureFood^® QUANTARD Allergen 40 reference material. The relative amount was assessed on a fish and béchamel sauce blend. Commercial food samples either labelled with or without fish in the ingredient list, were tested for the presence of fish DNA. The primer showed high specificity against the selected fish species. The limit of detection (LOD) and limit of quantification (LOQ) of the in-house method were 0.5 pg/µL and 5 pg/µL, respectively. The relative quantification in fish and béchamel blend samples detected a concentration as low as 0.000025%, corresponding to 0.25 mg/kg of fish, indicating the suitability of the method in a food matrix. The presence of fish DNA was always detected in commercial samples in which the presence of fish was listed in the ingredient list. The method was able to detect the presence of fish DNA also in samples in which the presence of fish was indicated as traces or was not declared on the label. The proposed method was demonstrated to be a reliable, specific, and sensitive method for the detection of fish allergens in foods. Therefore, the proposed real-time PCR method could be used as a useful instrument in the verification of compliance with allergen labelling regulations.

Sesame as a source of food allergens: clinical relevance, molecular characterization, cross-reactivity, stability toward processing and detection strategies

Sesame is an allergenic food with an increasing allergy prevalence among the European/USA population. Sesame allergy is generally life-persisting, being the cause of severe/systemic adverse immune responses in sesame-allergic individuals. Herein, clinical data about sesame allergy, including prevalence, diagnosis, relevance, and treatments are described, with focus on the molecular characterization of sesame allergens, their cross-reactivity and co-sensitization phenomena. The influence of food processing and digestibility on the stability/immunoreactivity of sesame allergens is critically discussed and the analytical approaches available for their detection in foodstuffs. Cross-reactivity between sesame and tree nuts or peanuts is frequent because of the high similarities among proteins of the same family. However, cross-reactivity phenomena are not always correlated with true clinical allergy in sensitized patients. Data suggest that sesame allergens are resistant to heat treatments and digestibility, with little effect on their immunoreactivity. Nevertheless, data are scarce, evidencing the need for more research to understand the effect of food processing on sesame allergenicity modulation. The demands for identifying trace amounts of sesame in foods have prompted the development of analytical methods, which have targeted both protein and DNA markers, providing reliable, specific, and sensitive tools, crucial for the effective management of sesame as an allergenic food.

Application of DNA barcoding for ensuring food safety and quality

With increasing international food trade, food quality and safety are high priority worldwide. The consumption of contaminated and adulterated food can cause serious health problems such as infectious diseases and allergies. Therefore, the authentication and traceability systems are needed to improve food safety. The mitochondrial DNA can be used for species authentication of food and food products. Effective DNA barcode markers have been developed to correctly identify species. The US FDA approved to the use of DNA barcoding for various food products. The DNA barcoding technology can be used as a regulatory tool for identification and authenticity. The application of DNA barcoding can reduce the microbiological and toxicological risks associated with the consumption of food and food products. DNA barcoding can be a gold-standard method in food authenticity and fraud detection. This review describes the DNA barcoding method for preventing food fraud and adulteration in meat, fish, and medicinal plants.

Development of a sandwich enzyme-linked immunosorbent kit for reliable detection of milk allergens in processed food

The inclusion of undeclared cow's milk proteins may cause health complications to milk-allergic consumers and is one of the leading cause of food recall in many countries all over the world. Therefore, to keep control on such incidences in processed products, we established a milk sandwich ELISA test kit by incorporating two polyclonal antibodies against milk proteins obtained from different species. Its analytical effectiveness in terms of sensitivity, specificity, accuracy, trueness, and precision were all analyzed. The limit of detection (LOD) of the test kit was 0.011 ppm, with high specificity for milk protein residues. The test kit was highly specific, apart from considerable cross-reactivity with goat milk and minor cross-reactivity with donkey and horse milk. The coefficient of variation of the test kit for intra-assay ranged from 4.02% to 14.62% and inter-assay ranged from 6.05% to 15.08% respectively. The sandwich ELISA was highly specific in detecting commercial food products. In a limited retail survey, 5/6 of the milk proteins declared on the ingredient labels tested positive for milk proteins. The study offers effective technical support for the sensitive detection of milk products both for food manufacturers and regulatory authorities.

Detection of Allergenic Proteins in Foodstuffs: Advantages of the Innovative Multiplex Allergen Microarray-Based Immunoassay Compared to Conventional Methods

Several factors can affect the allergen content and profile of a specific food, including processing procedures often leading to a decrease in allergenicity, although no change, or even an increase, have also been reported. Evaluation of the effectiveness of a processing procedure requires the availability of reliable methodologies to assess the variation in molecules able to induce allergic reactions in the analyzed food. Conventional and innovative strategies and methodologies can be exploited to identify allergenic proteins in foodstuffs. However, depending on the specific purposes, different methods can be used. In this review, we have critically reviewed the advantages of an innovative method, the multiplex allergen microarray-based immunoassay, in the detection of allergens in foodstuffs. In particular, we have analyzed some studies reporting the exploitation of an IgE-binding inhibition assay on multiplex allergen biochips, which has not yet been reviewed in the available literature. Unlike the others, this methodology enables the identification of many allergenic proteins, some of which are still unknown, which are recognized by IgE from allergic patients, with a single test. The examined literature suggests that the inhibition test associated with the multiplex allergen immunoassay is a promising methodology exploitable for the detection of IgE-binding proteins in food samples.

Tree Nuts and Peanuts as a Source of Beneficial Compounds and a Threat for Allergic Consumers: Overview on Methods for Their Detection in Complex Food Products

Consumption of tree nuts and peanuts has considerably increased over the last decades due to their nutritional composition and the content of beneficial compounds. On the other hand, such widespread consumption worldwide has also generated a growing incidence of allergy in the sensitive population. Allergy to nuts and peanuts represents a global relevant problem, especially due to the risk of the ingestion of hidden allergens as a result of cross-contamination between production lines at industrial level occurring during food manufacturing. The present review provides insights on peanuts, almonds, and four nut allergens—namely hazelnuts, walnuts, cashew, and pistachios—that are likely to cross-contaminate different food commodities. The paper aims at covering both the biochemical aspect linked to the identified allergenic proteins for each allergen category and the different methodological approaches developed for allergens detection and identification. Attention has been also paid to mass spectrometry methods and to current efforts of the scientific community to identify a harmonized approach for allergens quantification through the detection of allergen markers.

Food Allergies: Immunosensors and Management

Food allergies (FA) are commonly depicted as immune responses. The mechanism of allergic reactions involves immunoglobulin E (IgE) and non-immunoglobulin E (non-IgE)-related responses caused by contact with specific foods. FAs can be fatal, have negative effects and have become the subject of fanaticism in recent years. In terms of food safety, allergic compounds have become a problem. The immune response to allergens is different to that from food intolerance, pharmacological reactions, and poisoning. The most important allergenic foods are soybeans, milk, eggs, groundnuts, shellfishes, tree nuts, cereals and fish, which together are known as the “Big Eight”. This review will introduce and discuss FAs in milk, peanuts, nuts, shellfishes, eggs and wheat and their detections and potential treatments will also be provided. We believe that this review may provide important information regarding food-induced allergies for children who have allergic reactions and help them avoid the allergenic food in the future.

Naked-eye detection strategies coupled with isothermal nucleic acid amplification techniques for the detection of human pathogens

Nucleic acid amplification-based techniques have gained acceptance by the scientific, and general, community as reference methodologies for many different applications. Since the development of the gold standard of these techniques, polymerase chain reaction (PCR), back in the 1980s many improvements have been made, and alternative techniques emerged reporting improvements over PCR. Among these, isothermal amplification approaches resulted of particular interest as could overcome the need of specialized equipment to accurately control temperature changes, but it was after year 2000 that these techniques have flourished in a huge number of novel alternatives with many different degrees of complexities and requirements. An added value is their possibility to be combined with many different naked-eye detection strategies, simplifying the resources needed, allowing to reduce cost, and serving as the basis for novel developments of lab-on-chip systems, and miniaturized devices, for point-of-care testing. In this review, we will go over different types of naked-eye detection strategies, combined with isothermal amplification. This will provide the readers up-to-date information for them to select the most appropriate strategies depending on the particular needs and resources for their experimental setup.

Selecting processing robust markers using high resolution mass spectrometry for the detection of milk in food products

BACKGROUND

Cow's milk allergy is one of the most reported food allergies in Europe. To help patients suffering from food allergies it is important to be able to detect milk in different foods. An analytical method that is gaining interest in the field of allergen detection is Ultra-High Performance Liquid Chromatography-tandem Mass Spectrometry, where the analyte is a target peptide. When these peptide biomarkers are selected the effect of food processing should be taken into account to allow a robust detection method.

OBJECTIVE

This works aims at identifying such processing stable peptide markers for milk for the Ultra-High Performance Liquid Chromatography-tandem Mass Spectrometry based detection of food allergens in different food products.

METHODS

Milk-incurred food materials that underwent several processing techniques were produced. This was followed by establishing tryptic peptide profiles from each matrix using Ultra-High Performance Liquid Chromatography-High Resolution Mass Spectrometry .

RESULT

A careful comparison of peptide profiles/intensities and the use of specific exclusion criteria resulted in the selection of 8 peptide biomarkers suitable for application in Ultra-High Performance Liquid Chromatography-tandem Mass Spectrometry based milk detection methods. One of these markers is a α-lactalbumin specific peptide, which has been determined to be stable in different incurred materials for the first time.

CONCLUSION

To our knowledge, this is the first systematic and experimentally based approach for the selection of suitable milk peptide biomarkers robust towards multiple, often applied food processing techniques for milk. Ensuring the exact knowledge of the food processing circumstances by starting from well-defined raw material and using fully controlled settings to produce incurred test material allowed the construction of a peptide database with robust markers. These robust markers can be used for the development of a robust detection method for milk in different food matrices.

Development and evaluation of a novel loop mediated isothermal amplification coupled with TaqMan probe assay for detection of genetically modified organism with NOS terminator

In this study, we aim to develop a novel loop mediated isothermal amplification (LAMP) coupled with TaqMan (LAMP-TaqMan) method for quick qualitative detection of genetically modified organism (GMOs). We designed four LAMP primers and one TaqMan probe for the LAMP-TaqMan detection method to detect the nopaline synthase gene (NOS) terminator in GMOs. This assay enabled the amplification of DNA within ~20 min at a constant temperature of 65 °C. This assay detected as few as five copies of target sequences, which had a high specificity similar to the TaqMan qPCR method. Furthermore, the LAMP-TaqMan detection method was successfully used to amplify and detect DNA from food samples of the major crops (soybean, maize, rice, etc.). In summary, a novel LAMP-TaqMan assay has been developed, which has the similar sensitivity but takes less time than the TaqMan qPCR method. This method offers a novel approach for rapid detection of GMOs in foods.

Visual detection of tropomyosin, a major shrimp allergenic protein using gold nanoparticles (AuNPs)-assisted colorimetric aptasensor

A gold nanoparticle-based label-free colorimetric assay was developed to detect the shrimp allergenic protein tropomyosin (TM), an important biomarker responsible for severe clinical reactivity to shellfish. In a gold nanoparticles (AuNPs)-tropomyosin-binding aptamer (TMBA) complex, the aptamer adsorbs onto the surface of AuNPs and dissociates in the presence of TM. In addition, AuNPs tend to aggregate in the presence of ionic salt, revealing a color change (i.e., wine-red to purple/blue) with a shift in the maximum absorption peak from 520 nm. In the presence of specific binding TM, the aptamer folds into a tertiary structure where it more efficiently stabilizes AuNPs toward the salt-induced aggregation with a hypsochromic shift in the absorption spectra compared to the stabilized AuNPs by aptamer alone. Based on the aggregation and sensitive spectral transformation principle, the AuNPs-based colorimetric aptasensor was successfully applied to detect TM with a range of 10-200 nmol/L and a low detection limit of 40 nmol/L in water samples. The reliability, selectivity, and sensitivity of the aptasensor was then tested with food samples spiked with TM. The observed detection limit was as low as 70 nmol/L in shrimp, 90 nmol/L in tofu, and 80 nmol/L in eggs, respectively. We anticipate the proposed AuNPs-based colorimetric aptasensor assay possesses a high potential for the easy and efficient visual colorimetric detection of TM.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-020-00085-5.

Whey allergens: Influence of nonthermal processing treatments and their detection methods

Whey and its components are recognized as value-added ingredients in infant formulas, beverages, sports nutritious foods, and other food products. Whey offers opportunities for the food industrial sector to develop functional foods with potential health benefits due to its unique physiological and functional attributes. Despite all the above importance, the consumption of whey protein (WP) can trigger hypersensitive reactions and is a constant threat for sensitive individuals. Although avoiding such food products is the most successful approach, there is still a chance of incorrect labeling and cross-contamination during food processing. As whey allergens in food products are cross-reactive, the phenomenon of homologous milk proteins of various species may escalate to a more serious problem. In this review, nonthermal processing technologies used to prevent and eliminate WP allergies are presented and discussed in detail. These processing technologies can either enhance or mitigate the impact of potential allergenicity. Therefore, the development of highly precise analytical technologies to detect and quantify the existence of whey allergens is of considerable importance. The present review is an attempt to cover all the updated approaches used for the detection of whey allergens in processed food products. Immunological and DNA-based assays are generally used for detecting allergenic proteins in processed food products. In addition, mass spectrometry is also employed as a preliminary technique for detection. We also highlighted the latest improvements in allergen detection toward biosensing strategies particularly immunosensors and aptasensors.

Comparison of real-time PCR and ELISA for the detection of crustacean shellfish allergens

Food allergies are a significant public health concern, and crustacean shellfish represent one of the major FDA regulated food allergens. Allergic individuals must avoid foods containing crustaceans, and this necessitates highly sensitive and accurate detection methods. Two of the major methods used are protein-based ELISA and DNA-based real-time PCR. In order to properly compare these very different methodologies, we used identical split samples for a side-by-side comparison and analysed them using four different real-time PCR methods and two different commercial ELISA kits. Three real-time PCR assays targeting the mitochondrial 12S genes of shrimp, crab, and lobster were compared to a commercial ELISA assay for total crustacean protein. A fourth real-time PCR assay targeting the tropomyosin gene of shrimp was compared to an ELISA assay for shrimp tropomyosin. All comparisons were carried out in two different food matrices: Manhattan clam chowder and fish sauce. PCR assays had a more broad dynamic range (0.1-10⁶ mg/kg) as compared to ELISA (200-4000 mg/kg) and did not show matrix interference like ELISA. In cases where the ELISA assays did not have matrix interference, there was good qualitative agreement between PCR and ELISA.

Development of a Microfluidic Paper-Based Immunoassay for Rapid Detection of Allergic Protein in Foods

Food allergy affects up to 10% of the population, causing moderate to severe systemic symptoms and even death. Detecting allergens in food is the most critical and effective measure to reduce food allergy incidents, but the most commonly used kits, lateral flow immunoassay (LFI), are still relatively high in cost for the food industry. Microfluidic paper-based analytical devices (μPADs) demonstrate the potential to address this challenge by substituting the multiple parts/materials in LFI with solely (cellulose) paper as the platform. This study reports the development of a single-piece lateral flow μPAD and demonstrates its capability of detecting allergic protein in various food samples within a 15 min including sample preparation. A confined reagent deposition on the testing zone of the patterned paper was achieved by blade cutting. Surface modification of the cellulose was optimized to enable the complete release of recognizing conjugates and elimination of background noise. The geometry of patterns was optimized to meet the liquid sample's requirement in flow rate. This LFI-format μPAD can detect as low as 1 ppm ovalbumin in standard solution, 0.01% (w/w) egg white protein in spiked cake mix, and the egg content in other commercial food products. Much simpler fabrication procedures and a lower material cost are required by the μPAD than that by conventional LFIs. With the potential to scale up, this study provides an alternative food monitoring option to many sectors throughout the agri-food chain and contributes to improving food safety and public health.

Lupine allergens: Clinical relevance, molecular characterization, cross-reactivity, and detection strategies

Lupine is commonly utilized as a technological food and ingredient in a great variety of processed products (snacks, bakery, meat, and dairy products) principally owing to its nutritional value and technological properties. However, its ingestion, even at trace amounts (in the range of mg protein per kg of food), can lead to severe adverse reactions in allergic individuals. Lupine belongs to the Leguminosae family, having the conglutins (α-, β-, δ-, and γ-) as allergens, among other proteins. Cross-sensitization of lupine-sensitized individuals with other legume species, mainly peanut, can occur, but the associated clinical reactivity is still unclear. The protection of the sensitized individuals should depend on an avoidance diet, which should rely on the compliance of food labeling and, as such, on their verification by analytical methods. Food processing, such as heat treatments, has an important influence on the structural properties of lupine proteins, altering their detectability and allergenicity. In this review, different aspects related with lupine allergy are described, namely, the overall prevalence, clinical relevance, diagnosis, and treatment. The characterization of lupine allergens and their potential cross-reactivity with other legumes are critically discussed. The effects of food matrix, processing, and digestibility on lupine proteins, as well as the available analytical tools for detecting lupine at trace levels in foods, are also herein emphasized.

Production of a Recombinant Single-Domain Antibody for Gluten Detection in Foods Using the Pichia pastoris Expression System

The detection of gluten in foodstuffs has become a growing concern in food allergen management as a result of the high ratio of population sensitive to the main gluten-containing cereals. In this study, a promising single-domain antibody previously isolated by phage display (dAb8E) was produced in Pichia pastoris resulting in high levels of the antibody fragment expression (330 mg/L). The purified dAb8E was proved to specifically bind to gluten proteins from wheat, barley and rye, exhibiting no cross reaction to other heterologous species. The dynamic range of the sandwich enzyme-linked immunosorbent assay (ELISA) covered 0.1 to 10 µg/mL of gliadin, reaching a limit of detection of 0.12 µg/mL. When experimental binary mixtures of the target cereals were analyzed, the limit of detection was 0.13 mg/g, which would theoretically correspond to gluten concentrations of approximately 13 mg/kg. Finally, thirty commercially available food products were analyzed by means of the developed assay to further confirm the applicability of the dAb8E for gluten determination. The proposed methodology enabled the generation of a new gluten-specific nanobody which could be used to guarantee the appropriate labelling of gluten-free foods.

A Systematic Review of Food Allergy: Nanobiosensor and Food Allergen Detection

Several individuals will experience accidental exposure to an allergen. In this sense, the industry has invested in the processes of removing allergenic compounds in food. However, accidental exposure to allergenic proteins can result from allergenic substances not specified on labels. Analysis of allergenic foods is involved in methods based on immunological, genetic, and mass spectrometry. The traditional methods have some limitations, such as high cost. In recent years, biosensor and nanoparticles combined have emerged as sensitive, selective, low-cost, and time-consuming techniques that can replace classic techniques. Nevertheless, each nanomaterial has shown a different potential to specific allergens or classes. This review used Preferred Reporting Items for Systematic Reviews and the Meta-Analysis guidelines (PRISMA) to approach these issues. A total of 104 articles were retrieved from a standardized search on three databases (PubMed, Scopus and Web of Science). The systematic review article is organized by the category of allergen detection and nanoparticle detection. This review addresses the relevant biosensors and nanoparticles as gold, carbon, graphene, quantum dots to allergen protein detection. Among the selected articles it was possible to notice a greater potential application on the allergic proteins Ah, in peanuts and gold nanoparticle-base as a biosensor. We envision that in our review, the association between biosensor and nanoparticles has shown promise in the analysis of allergenic proteins present in different food samples.

Method for the Identification of Plant DNA in Food Using Alignment-Free Analysis of Sequencing Reads: A Case Study on Lupin

Fast and reliable analytical methods for the identification of plants from metagenomic samples play an important role in identifying the components of complex mixtures of processed biological materials, including food, herbal products, gut contents or environmental samples. Different PCR-based methods that are commonly used for plant identification from metagenomic samples are often inapplicable due to DNA degradation, a low level of successful amplification or a lack of detection power. We introduce a method that combines metagenomic sequencing and an alignment-free k-mer based approach for the identification of plant DNA in processed metagenomic samples. Our method identifies plant DNA directly from metagenomic sequencing reads and does not require mapping or assembly of the reads. We identified more than 31,000 Lupinus-specific 32-mers from assembled chloroplast genome sequences. We demonstrate that lupin DNA can be detected from controlled mixtures of sequences from target species (different Lupinus species) and closely related non-target species (Arachis hypogaea, Glycine max, Pisum sativum, Vicia faba, Phaseolus vulgaris, Lens culinaris, and Cicer arietinum). Moreover, these 32-mers are detectable in the following processed samples: lupin flour, conserved seeds and baked cookies containing different amounts of lupin flour. Under controlled conditions, lupin-specific components are detectable in baked cookies containing a minimum of 0.05% of lupin flour in wheat flour.

Food allergens: Classification, molecular properties, characterization, and detection in food sources

Food allergy is a large and growing public health problem in many areas of the world. The prevalence of food allergy has increased in the last decades in a very significant way in many world regions, particularly in developed countries. In that respect, the research field of food allergy has experienced an extensive growth and very relevant progress has been made in recent years regarding the characterization of food allergens, the study of their immunological properties, and their detection in food sources. Furthermore, food labeling policies have also been improved decidedly in recent years. For that immense progress made, it is about time to review the latest progress in the field of food allergy. In this review, we intend to carry out an extensive and profound overview regarding the latest scientific advances and knowledge in the field of food allergen detection, characterization, and in the study of the effects of food processing on the physico-chemical properties of food allergens. The advances in food labeling policies, and methodologies for the characterization of food allergens are also thoroughly reviewed in the present overview.

Nano-Biosensing Platforms for Detection of Cow's Milk Allergens: An Overview

Among prevalent food allergies, cow milk allergy (CMA) is most common and may persist throughout the life. The allergic individuals are exposed to a constant threat due to milk proteins' presence in uncounted food products like yogurt, cheese, and bakery items. The problem can be more severe due to cross-reactivity of the milk allergens in the food products due to homologous milk proteins of diverse species. This problem can be overcome by proper and reliable food labeling in order to ensure the life quality of allergic persons. Therefore, highly sensitive and accurate analytical techniques should be developed to detect the food allergens. Here, significant research advances in biosensors (specifically immunosensors and aptasensors) are reviewed for detection of the milk allergens. Different allergic proteins of cow milk are described here along with the analytical standard methods for their detection. Additionally, the commercial status of biosensors is also discussed in comparison to conventional techniques like enzyme-linked immunosorbent assay (ELISA). The development of novel biosensing mechanisms/kits for milk allergens detection is imperative from the perspective of enforcement of labeling regulations and directives keeping in view the sensitive individuals.

The role of incurred materials in method development and validation to account for food processing effects in food allergen analysis

The issue of undeclared allergens represents a matter of great concern, being the subject of many alert notifications by the Rapid Alert System for Food and Feed portal of the European Commission, often leading to food recalls. The availability of reliable analytical approaches able to detect and quantify hidden allergens in processed foods is increasingly requested by the food industry, food safety authorities and regulatory bodies to protect sensitive consumers' health. The present review discusses the fundamental role of incurred materials for method development and analytical performance assessment in a metrology perspective on testing for undeclared allergens in processed foodstuffs. Due to the nature of the analytes and their susceptibility to various processing effects, reliability and comparability of results have posed a great challenge. In this context, the use of incurred samples as reference materials permits simulation of the effects of food processing on target analyte structure affecting analyte extractability and detectability. Graphical abstract ᅟ.