Development of a rapid dipstick immunoassay for the detection of peanut contamination of food

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Abstract
Polyclonal antisera were raised to conarachin, the 7S globulin of peanut, Arachis hypogea. The antisera were of high titre and were specific for conarachin, showing no significant cross‐reaction with proteins from a range of nuts and legumes, as determined by immunoblotting and ELISA. A dipstick ELISA was developed using these antisera as both the capture and detector elements of the assay. The final steps utilized an avidin‐biotin detection system and tetramethylbenzidine as the substrate. The dipstick assay was highly sensitive, and employed a simple one‐step extraction method. It was able to detect as little as 0.01% (w/w) of peanut in marzipan and 0.1% (w/w) of peanut in chocolate. Roasted nuts were also detected, down to a concentration of 0.1% (w/w) in both foods. The dipstick assay also functioned with a range of foodstuffs, and readily indicated any that contained peanut. This method enables analysts to test, for the first time, for the presence of peanuts in food in a fast and easy‐to‐use manner. The availability of such technology makes the task of monitoring foods for contamination by peanuts readily achievable, providing the industry with an important tool for quality control of raw materials, processes and products. Increased testing will give consumers, particularly those sensitive to this potent allergen, increased assurance as to the safety of the food they eat.