Use of the indirect competitive ELISA for the detection of Brazil nut in food products Alfonso Clemente, Stephen J. Chambers, Federica Lodi, Claudio Nicoletti, Gary M. Brett * Nutrition and Consumer Sciences Division, Institute of Food Research, Norwich Research Park, Colney, Norwich NR4 7UA, UK Received 6 May 2002; received in revised form 21 January 2003; accepted 23 January 2003 Abstract Food related allergic reactions following inadvertent ingestion are increasingly common, with nuts, including Brazil nut, placed firmly in the top 10 food groups whose presence within a product should be declared. The presence of hidden allergens as a result of adulteration or contamination of ingredients presents a problem for both the food industry and the consumer. A sensitive and specific immunoassay for Brazil nut is described with a limit of detection of 1 ppm. Based upon the detection of the abundant 2S protein the assay is suitable for detection of raw and roasted Brazil nut in a range of food matrices. Ó 2003 Elsevier Ltd. All rights reserved. Keywords: Allergy; Brazil nut; Immunoassay 1. Introduction Incidents of hypersensitivity reaction to Brazil nut are reported with increasing frequency (Bourrier, Villevi- eille, Albertini, & Boutte, 2001; Dutau, Rittie, Rance, Juchet, & Bremont, 1999; Pumphrey, Wilson, Faragher, & Edwards, 1999; Sicherer & Sampson, 2000). It is in- cluded in the top 10 food groups implicated in food- induced anaphylaxis and among the recommended foods whose presence should be declared on labelling, irrespective of quantity (Hourihane, 1998). Brazil nut is a classical food allergen able to trigger an IgE mediated hypersensitivity reaction, the severity of which can vary from mild laryngeal irritation to anaphylaxis. Brazil nut can be grouped with peanut, other tree nuts, fish and shellfish as lifelong food sensitivities with no developed tolerance of the type often observed with egg or milk allergy (Sampson, 1998a, 1998b). The only current way for the susceptible individual to avoid an allergic reaction is lifelong avoidance of the causative food. Like peanut, Brazil nut is commonly used as a minor ingredient in processed foods (i.e. biscuits, cakes and confectionery products) and consequently not al- ways included on the product label; as such there is the possibility of accidental consumption. Similarly, con- tamination at any stage of the food chain may introduce hidden allergens. To combat this there is increasing use of defensive labelling such as ‘‘this product may contain nuts’’ even though these are not declared in the list of ingredients. There are many reported cases of accidental consumption of peanut possibly as the result of con- tamination of either the raw material or during pro- cessing such as in the switch-over between a peanut containing and a nut-free food produced on the same equipment (Hourihane, 1997; Huggett & Hischenhuber, 1998; Loza & Brostoff, 1995; Sampson, 1996). There are no reports available to us of accidental consumption due to contamination by Brazil nut, however with its in- creased use in the food industry as a minor ingredient in products e.g. mince pies, there is a real need to monitor production processes. Although the amount of allergen required to provoke a response will vary from one individual to another, it is generally accepted that a few milligrams or possibly microgram amounts are sufficient (Hourihane, 1998; Hourihane et al., 1997). As a consequence there is a need for sensitive methods to detect potential allergen sources in foodstuffs. Immunochemical methods offer the nec- essary sensitivity and specificity for detecting traces of protein sources in foods. Enzyme immunoassays are already used for the detection of peanut (Hefle, Bush, Yunginger, & Chu, 1994; Mills, Pots, Plumb, Lambert, & Morgan, 1997; Yeung & Collins, 1996), egg (Eriksson * Corresponding author. Tel.: +44-1603-255000; fax: +44-1603- 507723. E-mail address: gary.brett@bbsrc.ac.uk (G.M. Brett). 0956-7135/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0956-7135(03)00017-3 Food Control 15 (2004) 65–69 www.elsevier.com/locate/foodcont