Rocket immunoelectrophoresis (RIE) for determination of potentially allergenic peanut proteins in processed foods as a simple means for quality assurance and food safety

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.

Food allergen detection methods and the challenge to protect food-allergic consumers

The detection of allergenic ingredients in food products has received increased attention from the food industry and legislative and regulatory agencies over recent years. This has resulted in the improvement of measures aimed at the protection of food-allergic consumers. The controlled production of food products and control activities executed by food inspection agencies rely on the availability of methods capable of detecting traces of allergenic ingredients. The development of such methods faces a multitude of analytical challenges. Those challenges will be identified and discussed in this review. Furthermore, future developments and trends in analytical methodology as applied to the detection of food allergens are reported.

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.

Allergenicity of refined vegetable oils

Several commercially important refined vegetable oils are derived from plants which are recognized as potent food allergens (e.g. peanut, soy). Full refining of oils results in the almost complete removal from oils of protein, which is responsible for allergic reactions. However, it is uncertain whether the minute amounts remaining could provoke allergic reactions in highly susceptible individuals. This has led to a vigorous debate about the safety of refined oils and specifically whether to label each oil individually because of the potential risk of allergenicity. Peanut oil has been the most thoroughly studied. It has been shown, in well-designed studies, that refined peanut oil can be safely consumed by the vast majority of peanut-allergic individuals, whereas unrefined oil can provoke reactions in some of the same individuals. However, some other studies report cases of allergic individuals reacting to oils, which are presumed to be refined. While it is likely that the discrepancy between these observations is due to differences in the processing of the oils, and possibly the protein content, this has not been formally demonstrated. Few data exist on the potential allergenicity of other edible vegetable oils; what data there are suggest that the major oils (soy, maize, sunflower, palm) do not provoke allergic reactions in susceptible individuals. Determining the content and immunoreactivity of the residual protein of refined oils is crucial to assessing the allergenic risk they present. Current methodology is inadequate and has not been validated for use with oils and aqueous extracts from oils. Little is known about the importance of different processing steps on allergenicity, although this information is crucial to risk assessment, particularly when considering process modifications. Available data suggest that the protein content of crude oils is of the order of 100-300 microg and that refining results in levels up to about 100-fold lower. The review concludes that peanut oil, and by extrapolation other edible vegetable oils, presents no risk of provoking allergic reactions in the overwhelming majority of susceptible people. However, there is a need to standardize and validate methodology for measuring the protein content and immunoreactivity of such so that they can be used to maintain process specifications. Thresholds of reactivity to allergens in man also need to be established in order to assess fully the risk from very small amounts.

Indirect competitive ELISA for determination of traces of peanut (Arachis hypogaea L.) protein in complex food matrices

An indirect competitive ELISA was developed allowing the detection of hidden peanut protein residues down to 2 ppm (micorgrams per gram) in various foods. The high-titer, peanut-specific polyclonal antiserum used recognized potentially allergenic proteins in both native and roasted peanuts. In the absence of a food matrix, extractable protein from roasted peanuts was detected at 104 +/- 13%. From various food items, peanut protein at > or =13 ppm was recovered between 84 and 126%, and at 2 ppm of peanut protein recovery was 143 +/- 6%. Intra- and interassay precision was <15%. In 5 of 17 commercial food products without declaration of peanut components, between 2 and 18 ppm of peanut protein was detected. This is the first assay based on commercially available reactants that allows the reliable determination of trace amounts of hidden peanut allergens in a variety of complex food matrices.