Development of a sandwich enzyme-linked immunosorbent assay for the detection of egg residues in processed foodst

Multiphoton lithography with protein photoresists

Recently, 2D/3D direct laser writing has attracted increased attention due to its broad applications ranging from biomedical engineering to aerospace. 3D nanolithography of water-soluble protein-based scaffolds have been envisioned to provide a variety of tunable properties. In this paper, we present a functional protein-based photoresist with tunable mechanical properties that is suitable for multiphoton lithography (MPL). Through the use of methacrylated streptavidin or methacrylated bovine serum albumin in combination with polyethylene glycol diacrylate or methacrylated hyaluronic acid as crosslinkers and a vitamin-based photoinitiator, we were able to write two- and three-dimensional structures as small as 200 nm/600 nm lateral/axial features, respectively. We also demonstrated that Young's modulus can be tuned by the photoresist composition, and we were able to achieve values as low as 40 kPa. Furthermore, we showed that Young's modulus can be recovered after drying and rehydration (i.e. shelf time determination). The retained biological functionality of the streptavidin scaffolds was demonstrated using fluorescently labelled biotins. Using single-molecule fluorescence microscopy, we estimated the density of streptavidin in the written features (1.8 ± 0.2 × 105 streptavidins per 1.00 ± 0.05 μm³ of feature volume). Finally, we showed applicability of our 2D scaffold as a support for a fluorescence absorbance immuno-assay (FLISA), and as a delivery platform of extracellular vesicles to HeLa cells.

A sandwich ELISA for the detection of mollusks and mollusk products

Mollusks are a major allergenic food under the food allergen regulations of many countries and must be declared on food products to reduce the risk of allergic reactions. However, a reliable immunoassay for detecting edible mollusks (cephalopods, gastropods, and bivalves) has not been reported. In this study, the developed sandwich enzyme-linked immunosorbent assay (sELISA) detected 32 edible mollusk species in raw and heated without cross-reaction with non-mollusk species. The detection limits of the assay were 0.1 ppm for heated mollusks and 0.1-0.5 ppm for raw mollusks, depending on the mollusk species tested. The inter-assay and intra-assay coefficients of variation (CVs) were ≤14.83 and ≤8.11, respectively. The assay detected steamed, boiled, baked, fried, and autoclaved mollusk samples and all commercial mollusk products tested. In this study, we developed a mollusk-specific sELISA to protect people allergic to mollusks.

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.

Development of a sensitive sandwich-ELISA assay for reliable detection of fish residues in foods

A new sandwich-type Enzyme-Linked Immunosorbent Assay (ELISA) method was developed based on goat IgG as capturing antibody and rabbit IgG as detecting antibody targeting soluble antigenic fish proteins in foods as detection targets. The assay has provided a relatively lower limit of quantitation (LoQ) for fish proteins with LoQ 0.5 ng/ml and appears highly sensitive. The analysis of 24 different substances, both raw and boiled, revealed no cross-reactivity above the cut-off point of the limit of quantitation. Recoveries of the SB spiked food matrixes were in the range of 83-131%. Assay precision testing proved that repeatability (<5%) and reproducibility (<11%) had an acceptable level of variation. The sandwich ELISA was capable of detecting all tested commercially important fish. As a potential analytical tool, the newly developed immunoenzymatic method is suitable for detecting undeclared fish residues in real food samples available in the market, thereby will help to reduce the incidents of fish allergies.

Development of a Sandwich Enzyme-Linked Immunosorbent Assay for Detection and Quantification of Clam Residues in Food Products

Seafood is a frequent cause of allergic reactions to food globally. The presence of undeclared trace amounts of clam can cause allergic reactions in sensitive individuals. Limited tools are available to test food products for the presence of traces of clam. We report on the development of a sandwich ELISA that can detect and quantify clam protein in food. Antisera against a mix of two commercially important clam species, Atlantic Surf (Spisula solidissima) and ocean quahog (Arctica islandica), were raised in rabbit and sheep. A sandwich ELISA was constructed with this antisera, and sensitivity and specificity were evaluated. Also, model food products spiked with clam protein were analyzed to assess the performance of the ELISA. Comparison was made with a commercially available ELISA for crustacea. The lower limit of quantification of the sandwich ELISA is 2.5 ppm clam protein in food samples, allowing the detection of low amounts of clam that may trigger a reaction in clam allergic patients. The sandwich ELISA was highly specific with cross-reactivity only noted for other molluscan shellfish (mussel and scallop). Clam protein in tomato juice and potato cream soup was detected well with recoveries ranging from 65 to 74% and from 74 to 113%, respectively. However when potato cream soup was retorted, the recover fell to 20%, imposing the risk of underestimating the clam content of a food product. A commercially available crustacean ELISA test was not suitable to detect clam protein. The sandwich ELISA described here is suitable for detection and quantification of clam protein in food products. Care should be taken with food products that have been retorted as the results may be underestimated.

Are current analytical methods suitable to verify VITAL® 2.0/3.0 allergen reference doses for EU allergens in foods?

Food allergy affects up to 6% of Europeans. Allergen identification is important for the risk assessment and management of the inadvertent presence of allergens in foods. The VITAL® initiative for voluntary incidental trace allergen labeling suggests protein reference doses, based on clinical reactivity in food challenge studies, at or below which voluntary labelling is unnecessary. Here, we investigated if current analytical methodology could verify the published VITAL® 2.0 doses, that were available during this analysis, in serving sizes between 5 and 500 g. Available data on published and commercial ELISA, PCR and mass spectrometry methods, especially for the detection of peanuts, soy, hazelnut, wheat, cow's milk and hen's egg were reviewed in detail. Limit of detection, quantitative capability, matrix compatibility, and specificity were assessed. Implications by the recently published VITAL® 3.0 doses were also considered. We conclude that available analytical methods are capable of reasonably robust detection of peanut, soy, hazelnut and wheat allergens for levels at or below the VITAL® 2.0 and also 3.0 doses, with some methods even capable of achieving this in a large 500 g serving size. Cow's milk and hen's egg are more problematic, largely due to matrix/processing incompatibility. An unmet need remains for harmonized reporting units, available reference materials, and method ring-trials to enable validation and the provision of comparable measurement results.

Implementation of an Enzyme Linked Immunosorbent Assay for the Quantification of Allergenic Egg Residues in Red Wines Using Commercially Available Antibodies

Since the early 2000s, labeling of potentially allergenic food components to protect people who suffer from food allergies is compulsory in numerous industrialized countries. In Europe, milk and egg components used during the winemaking process must be indicated on the label since July 1, 2012. Several ELISA procedures have been developed to detect allergenic residues in wines. However, the complexity of the wine matrix can inhibit the immunoenzymatic reaction. The aim of this study was to implement an ELISA assay for the detection of ovalbumin in red wines using commercially available antibodies. The specificity of the acquired antibodies and the absence of cross reactivity were assessed by immunoblotting and ELISA. An ELISA assay with a LOD of 14.2 μg/L and a LOQ of 56.4 μg/L of ovalbumin in aqueous solution was obtained. Differences in ELISA signals were observed when analyzing various fining agents, although reproducible conformation of the antigen could be reached for the comparison of ovalbumin and Ovicolle. The differences between samples in terms of pH could be leveled but the inhibition of the ELISA signal, positively correlated to the tannin content of the wines, could not be suppressed. Thus, standard curves of ovalbumin in several wines were obtained by relative quantification. The control steps and the difficulties encountered presented in this study should be considered by anybody working toward the development of ELISA assays for the detection of allergenic residues in complex food matrices.

Sandwich Enzyme-Linked Immunosorbent Assay for Detecting Sesame Seed in Foods

Small amounts of sesame can trigger allergic reactions in sesame-allergic patients. Because sesame is a widely used food ingredient, analytical methods are needed to support quality control and food safety programs in the food industry. In this study, polyclonal antibodies against sesame seed proteins were raised, and an enzyme-linked immunosorbent assay (ELISA) was developed for the detection and quantification of sesame seed residue in food. A comparison was made between this ELISA and other assays, particularly focusing on recovery of sesame seed residue from different food matrices. The developed ELISA is sensitive with a lower limit of quantification of 0.5 ppm and shows essentially no cross-reactivity with other foods or food ingredients (92 tested). The ELISA has a good recovery for analyzing sesame-based tahini in peanut butter, outperforming one other test. In a baked bread matrix, the ELISA has a low recovery, while two other assays perform better. We conclude that a sensitive and specific ELISA can be constructed based on polyclonal antibodies, which is suitable for detection of small amounts of sesame seed relevant for highly allergic patients. Furthermore, we conclude that different food products may require different assays to ensure adequate quantification of sesame.

Food production and processing considerations of allergenic food ingredients: a review

Although most consumers show no adverse symptoms to food allergens, health consequences for sensitized individuals can be very serious. As a result, the Codex General Standard for the Labelling of Prepackaged Foods has specified a series of allergenic ingredients/substances requiring mandatory declaration when present in processed prepackaged food products. Countries adhering to international standards are required to observe this minimum of eight substances, but additional priority allergens are included in the list in some countries. Enforcement agencies have traditionally focused their effort on surveillance of prepackaged goods, but there is a growing need to apply a bottom-up approach to allergen risk management in food manufacturing starting from primary food processing operations in order to minimize the possibility of allergen contamination in finished products. The present paper aims to review food production considerations that impact allergen risk management, and it is directed mainly to food manufacturers and policy makers. Furthermore, a series of food ingredients and the allergenic fractions identified from them, as well as the current methodology used for detection of these allergenic foods, is provided.

Development of a sandwich enzyme-linked immunosorbent assay (ELISA) for detection of buckwheat residues in food

Buckwheat is a pseudocereal (an eudicot with seed qualities and uses similar to those of monocot cereals, family Poaceae) that is consumed in some Asian countries as a staple, and in some western countries as a health food. Allergic reactions to buckwheat are common in some countries. The objective was to develop a specific and sensitive sandwich enzyme-linked immunosorbent assay (ELISA) to detect traces of buckwheat that might inadvertently contaminate other foods in order to assure accurate labeling and consumer protection. Buckwheat-specific antibodies produced in 3 species of animals were tested for specificity and titer by direct ELISA and immunoblot. A sandwich ELISA was developed utilizing pooled rabbit antibuckwheat sera to capture buckwheat proteins and pooled goat antibuckwheat sera, followed by enzyme-labeled rabbit antigoat immunoglobulin G (IgG), to detect bound buckwheat proteins. The lower limit of quantification (LOQ) of the sandwich ELISA was 2 parts per million (ppm) of buckwheat in the presence of complex food matrices. The ELISA is highly specific with no cross-reactivity to any of 80 food ingredients and matrices tested. Validation studies conducted with buckwheat processed into noodles and muffins showed greater than 90% and 60% recovery, respectively. The percent recovery of buckwheat from noodles was similar to that achieved with a commercial buckwheat ELISA kit (ELISA Systems Pty. Ltd., Windsor, Queensland, Australia) at high buckwheat concentrations. However, the sensitivity of this ELISA was greater than the commercial ELISA. This newly developed ELISA is sufficiently specific and sensitive to detect buckwheat residues in processed foods to protect buckwheat-allergic subjects from potential harm. Practical Application: Buckwheat is becoming a common food ingredient in a number of processed foods due to potentially beneficial nutritional properties, without the celiac disease inducing glutenin proteins of wheat and related cereals. However, buckwheat causes allergy in some individuals and must be labeled and tested accurately to protect those with allergy to buckwheat. We describe the development of a new test assay to help food producers ensure that buckwheat is not present in foods that are not intended to contain buckwheat.

Detection of mustard, egg, milk, and gluten in salad dressing using enzyme-linked immunosorbent assays (ELISAs)

Enzyme-linked immunosorbent assay (ELISA) is a commonly used method for the detection of trace amounts of potentially allergenic protein residues in foods. However, food matrices and processing conditions can affect the detection of protein residues. The effects of acidity on the detectability of several allergenic proteins commonly found in salad dressing using ELISAs was investigated. First, recovery experiments were performed on salad dressing formulated with 0 to 1000 ppm mustard flour (mustard). The mean percent recovery for mustard from the salad dressing was only 7.7%+/- 1.6%. When the pH of the salad dressing was adjusted to pH 7 prior to spiking with mustard, recovery improved to 94.1%+/- 7.6%. However, if the pH was adjusted to pH 7 after spiking and extraction, the recovery was only 11.1%+/- 1.7%. When vinegar was spiked with mustard flour at pH 3, 3.5, and 4, detectability of mustard was lowest at pH 3. Basic extraction of mustard proteins from salad dressing did not improve the mustard detection. Acidic salad dressing matrices reduced the detectability of mustard by the mustard ELISA probably because of acid precipitation of mustard proteins that renders them insoluble and nonextractable. Commercial salad dressings containing 100 ppm (mg/kg) of egg, milk, or gluten were analyzed every 2 to 4 d for 90 d using 3 commercially available ELISAs. A decrease in the detection of the egg, milk, and gluten in the salad dressing upon storage was observed. Our study highlighted the importance of evaluating the utility of various ELISAs for specific food matrices and the recovery as a function of product storage.

Recent advances in the understanding of egg allergens: basic, industrial, and clinical perspectives

The emergence of egg allergy has had both industrial and clinical implications. In industrialized countries, egg allergy accounts for one of the most prevalent food hypersensitivities, especially in children. Atopic dermatitis represents the most common clinical manifestation in infancy; however, the range of clinical signs is broad and encompasses life-threatening anaphylaxis. The dominant egg allergens are proteins and are mainly present in the egg white, for example, ovalbumin, ovomucoid, ovotransferrin, and lysozyme. However, egg yolk also displays low-level allergenicity, for example, alpha-livetin. Strict avoidance of the offending food remains the most common recommendation for egg-allergic individuals. Nevertheless, the omnipresence of egg-derived components in prepackaged or prepared foods makes it difficult. Therefore, more efficient preventive approaches are investigated to protect consumers from inadvertent exposure and ensuing adverse reactions. On the one hand, commercial kits have become readily available that allow for the detection of egg contaminants at trace levels. On the other hand, attempts to produce hypoallergenic egg-containing products through food-processing techniques have met with promising results, but the approach is limited due to its potentially undesirable effects on the unique functional and sensory attributes of egg proteins. Therefore, the development of preventive or curative strategies for egg allergy remains strongly warranted. Pilot studies have suggested that oral immunotherapy (IT) with raw or cooked preparations of egg may represent a safe alternative, immediately available to allergic subjects, but remains applicable to only nonanaphylactic patients. Due to the limitations of conventional IT, novel forms of immunotherapy are sought based on information obtained from the molecular characterization of major egg allergens. In the past decade, promising approaches to the treatment and prevention of egg allergy have been explored and include, among others, the production of hypoallergenic recombinant egg proteins, the development of customized peptides, and bacterial-mediated immunotherapy. Nonspecific approaches have also been evaluated, and preliminary trials with the use of probiotic bacteria have yielded encouraging results. The current understanding of egg allergens offers novel approaches toward the making of food products safe for human consumption and the development of efficient immunotherapeutic strategies.

Cleaning and other control and validation strategies to prevent allergen cross-contact in food-processing operations

Food allergies affect an estimated 10 to 12 million people in the United States. Some of these individuals can develop life-threatening allergic reactions when exposed to allergenic proteins. At present, the only successful method to manage food allergies is to avoid foods containing allergens. Consumers with food allergies rely on food labels to disclose the presence of allergenic ingredients. However, undeclared allergens can be inadvertently introduced into a food via cross-contact during manufacturing. Although allergen removal through cleaning of shared equipment or processing lines has been identified as one of the critical points for effective allergen control, there is little published information on the effectiveness of cleaning procedures for removing allergenic materials from processing equipment. There also is no consensus on how to validate or verify the efficacy of cleaning procedures. The objectives of this review were (i) to study the incidence and cause of allergen cross-contact, (ii) to assess the science upon which the cleaning of food contact surfaces is based, (iii) to identify best practices for cleaning allergenic foods from food contact surfaces in wet and dry manufacturing environments, and (iv) to present best practices for validating and verifying the efficacy of allergen cleaning protocols.

Specific and sensitive enzyme-linked immunosorbent assays for analysis of residual allergenic food proteins in commercial bottled wine fined with egg white, milk, and nongrape-derived tannins

Regulations introduced by the Food Standards Australia New Zealand in December 2002 require all wine and wine product labels in Australia to identify the presence of a processing aid, additive or other ingredient, which is known to be a potential allergen. The objective of this study was to establish sensitive assays to detect and measure allergenic proteins from commonly used processing aids in final bottled wine. Sensitive and specific enzyme-linked immunosorbent assays (ELISA) were developed and established for the proteins casein, ovalbumin, and peanut. Lower limits of detection of these proteins were 8, 1, and 8 ng/mL, respectively. A panel of 153 commercially available bottled Australian wines were tested by these ELISA, and except for two red wines known to contain added whole eggs, residuals of these food allergens were not detected in any wine. These findings are consistent with a lack of residual potentially allergenic egg-, milk-, or nut-derived processing aids in final bottled wine produced in Australia according to good manufacturing practice at a concentration that could cause an adverse reaction in egg, milk, or peanut/tree-nut allergic adult consumers.

Quantitative sandwich ELISA for the determination of lupine (Lupinus spp.) in foods

The use of lupine in foods has increased considerably during the past decade, reflected by a corresponding increase in reported lupine-induced allergic incidents. Lupine allergy may arise either by primary sensitization or by clinical cross-reactivity in peanut-allergic persons. Detection of lupine proteins in food has previously been based on the use of patient serum. A novel sandwich enzyme-linked immunosorbent assay (ELISA) for the detection and quantification of lupine in processed foods was developed, using a polyclonal rabbit antilupine capture antibody and a biotinylated conjugate of the same antibody for detection. The antibody was highly specific for lupine, apart from minor cross-reactivities to other legumes. The assay had a detection limit of 1 mug/g and was successfully used to quantify lupine protein in various food matrixes. Recoveries ranged from 60 to 116%, while the intra-and interassay coefficients of variation were <6% and <21%, respectively.

Information provision for allergic consumers--where are we going with food allergen labelling?

As the current treatment for food allergy involves dietary exclusion of the problem food, information for food-allergic consumers provided on food labels about the nature of allergenic ingredients is important to the management of their condition. The members of an EU-funded networking project, InformAll, focusing on developing strategies for the provision of credible, reliable sources of information for food allergy sufferers, regulators and the food industry, have been considering these matters with respect to food labelling. This paper presents an overview of the genesis of the new EU directive on food labelling, its relevance to food-allergic consumers and the problems that might arise if precautionary labelling becomes more widespread in response to concerns regarding inadvertent allergen contamination in foods. International efforts to define threshold levels of allergens able to trigger a reaction coupled with validated allergen detection methods are essential if the food industry is to implement effective hazard control procedures and address the problems of cross-contact allergens without devaluing the information provided to consumers on food labels.

Allergenic potency of spices: hot, medium hot, or very hot

Spices are the most attractive ingredients to confer an authentic taste to food. As they are derived from plants, they harbour allergenic potency and can induce symptoms ranging from mild local to severe systemic reactions. Due to the content of pharmacologically active substances of spices, the diagnosis of allergy and the differentiation from intolerance reactions may be difficult. Association with inhalative allergies via IgE cross-reactivity, but also direct gastrointestinal sensitization plays a role. This article is a botanical and allergological overview of the most important spices and molecules responsible for eliciting IgE-mediated reactions or cross-reactions. As no curative treatments are known at present, strict avoidance is recommended and, therefore, accurate labelling of pre-packed food is necessary.

Validated sandwich enzyme-linked immunosorbent assay for casein and its application to retail and milk-allergic complaint foods

Cows' milk is a commonly allergenic food. Cross-contamination of milk proteins into nondairy, kosher-pareve foods prepared on shared processing equipment can cause severe, life-threatening reactions in milk-allergic individuals. A sandwich-type enzyme-linked immunosorbent assay (ELISA; 96-well plate format) was developed for the detection of undeclared casein in foods. Rabbit anti-casein antibodies were used as the capture reagent. Food samples and standards were ground, extracted in 0.01 M phosphate-buffered saline, clarified by centrifugation, and added to the wells. Goat anti-casein antibodies were employed as the detector antibody, and the amount of antibody bound was determined with a commercial rabbit anti-goat immunoglobulin conjugated to alkaline phosphatase, with subsequent substrate reaction. Antibodies developed were specific to casein, with no cross-reaction observed with 30 foods and food ingredients. Non-milk-containing products such as fruit juices, fruit juice bars, sorbets, and dark and pareve-labeled chocolate were purchased from June 2002 through June 2003. In addition, samples allegedly causing eight milk-allergic consumer complaints were analyzed. The ELISA had a detection limit of less than 0.5 ppm of casein. The casein content in the analyzed foods ranged from less than 0.5 ppm to more than 40,000 ppm casein; undeclared casein residues were found in all of the samples implicated in allergic reactions. The levels of milk contamination in some of the other surveyed products could also be hazardous for milk-allergic consumers. This ELISA method provides a useful quality control tool for the food industry and could also be used as a validation of kosher-pareve status.

Food allergy and the food industry

Although most food-allergic reactions occur after ingestion of nonpackaged food products, the food industry has been subjected to increasing scrutiny of their allergen controls; the resulting impact on the industry has been remarkable. Undeclared food allergens have been responsible for many food product recalls during the past 13 years, and the food industry has made significant investment, effort, and improvements in allergen control during this time. Recently, tests for some allergenic foods have been commercialized, and proven useful to the industry in controlling allergens and helpful for regulatory agencies investigating food-allergic consumer complaints. However, testing methods still do not exist for some of the common allergenic foods. Labeling initiatives have been pursued to make ingredient listings more easily understood by food-allergic consumers, but further improvements could still be made. Additional research to determine eliciting doses for allergenic foods is needed to enable science-based risk assessment and risk management.

Peanut allergen (Ara h 1) detection in foods containing chocolate

Inadvertent exposure to peanut in foods poses health risks for peanut-allergic individuals that can be reduced by improving detection systems for allergen contaminants in food products and manufacturing processes. Detection of peanut in chocolate has been especially difficult. We report the optimization of conditions for measuring a major peanut allergen, Ara h 1, in chocolate with the use of a two-site monoclonal antibody sandwich enzyme-linked immunosorbent assay. Ara h 1 was extracted from peanut in the presence or absence of chocolate with phosphate buffer, salt, and three dried milks (goat, soy, or nonfat) (0 to 25% wt/vol) for 15 min at 60 degrees C or for 2.5 h at room temperature. The best conditions for Ara h 1 extraction in the presence of chocolate were 5% nonfat dry milk for 2.5 h at room temperature. Spiking experiments of chocolate with peanut confirmed improvement of the extraction: Ara h 1 was detected in extractions of 0.16 to 0.33% peanut in chocolate. Interestingly, the best conditions for Ara h 1 extraction were different for peanut alone than with chocolate, regarding time, temperature, and percentage of nonfat dry milk in the extraction buffer. In chocolate with peanut foods, the total Ara h 1 values were 10-fold higher than when products were extracted with phosphate buffer alone and could be up to 400-fold higher for individual foods. The dramatic improvement of Ara h 1 extraction should allow specific allergen monitoring in chocolate-containing food products and assessment of Ara h 1 exposure.

Methods for allergen analysis in food: a review

Food allergies represent an important health problem in industrialized countries. Undeclared allergens as contaminants in food products pose a major risk for sensitized persons. A proposal to amend the European Food Labelling Directive requires that all ingredients intentionally added to food products will have to be included on the label. Reliable detection and quantification methods for food allergens are necessary to ensure compliance with food labelling and to improve consumer protection. Methods available so far are based on protein or DNA detection. This review presents an up-to-date picture of the characteristics of the major food allergens and collects published methods for the determination of food allergens or the presence of potentially allergenic constituents in food products. A summary of the current availability of commercial allergen detection kits is given. One part of the paper describes various methods that have been generally employed in the detection of allergens in food; their advantages and drawbacks are discussed in brief. The main part of this review, however, focuses on specific food allergens and appropriate methods for their detection in food products. Special emphasis is given to allergenic foods explicitly mentioned in the Amendment to the European Food Labelling Directive that pose a potential risk for allergic individuals, namely celery, cereals containing gluten (including wheat, rye and barley) crustaceans, eggs, fish, peanuts, soybeans, milk and dairy products, mustard, tree-nuts, sesame seeds, and sulphite at concentrations of at least 10 mg kg(-1). Sulphites, however, are not discussed.

Monitoring peanut allergen in food products by measuring Ara h 1

BACKGROUND

Peanut allergy is an important health problem in the United States, affecting approximately 0.6% of children. Inadvertent exposure to peanut is a risk factor for life-threatening food-induced anaphylaxis.

OBJECTIVE

The purpose of this investigation was to develop an immunoassay for a major peanut allergen, Ara h 1, to detect peanut allergen in foods so that the risk of inadvertent exposure can be reduced.

METHODS

A specific 2-site monoclonal antibody-based ELISA was developed to measure Ara h 1 in foods. The sensitivity of the assay was 30 ng/mL. Ara h 1 was measured in foods (n = 83) with or without peanut and in experiments to optimize allergen yield and to determine peanut contamination in spiked foods.

RESULTS

Ara h 1 levels in food products ranged from less than 0.1 microg/g to 500 microg/g. Ara h 1 measured in ng/mL was transformed to microg/g for food products. Peanut butter contained the highest amounts of Ara h 1. Peanut extracts contained from 0.5 to 15 mg Ara h 1/g of peanut depending on the extraction conditions. Optimal extraction of Ara h 1 was obtained by using phosphate buffer with 1 mol/L NaCl and Tween at 60 degrees C. Ara h 1 was not always detected in presence of chocolate under the extraction conditions tested. Spiking experiments showed that the assay could detect approximately 0.1% Ara h 1 contamination of food with ground peanut. There was an excellent correlation between Ara h 1 levels and peanut content measured by using a commercial polyclonal antibody-based ELISA (r = 93, n = 31, P <.001).

CONCLUSION

A new sensitive and specific monoclonal antibody-based ELISA was used to monitor Ara h 1 content in food products. This assay should be useful for monitoring peanut contamination in the food manufacturing and processing industry and in developing thresholds for sensitization or allergic reaction in persons with peanut allergy.

Fluorophor-linked immunosorbent assay: a time- and cost-saving method for the characterization of antibody fragments using a fusion protein of a single-chain antibody fragment and enhanced green fluorescent protein

A novel assay, referred to as fluorophor-linked immunosorbent assay (FLISA), for the characterization of single-chain antibody fragments (scFvs) is described. The principle of the method is the fusion of an scFv to enhanced green fluorescent protein (EGFP). The scFv domain, which binds to the immobilized hapten, can be detected by measuring the fluorescence of the EGFP domain. The time-consuming binding of secondary antibodies and enzyme reaction, necessary for enzyme-linked immunosorbent assays (ELISAs) are not required. Consequently, the assay time of 1.5 h needed to complete the FLISA is much shorter than that of comparable ELISAs, which require about 5 h. This renders the FLISA suitable for applications where a short assay time is essential, such as screening of mutant libraries of scFvs in directed evolution experiments or monitoring of the amount of functionally expressed recombinant protein during production processes. In contrast to a comparable ELISA, the FLISA showed no saturation when determining the relative amount of functional scFv. The amount of the soluble fraction of cell extracts from Escherichia coli expressing the fusion protein and the normalized fluorescence signal showed a linear correlation with R(2)>0.99. The usefulness of a competitive FLISA for the detection of analytes is shown exemplarily by the detection of s-triazines with the s-triazine-specific scFv K411B.