Development of a highly sensitive and robust Cor a 9 specific enzyme-linked immunosorbent assay for the detection of hazelnut traces.

Allergy to tree nuts represents an acute health problem. Sensitized people can be inadvertently exposed to hidden allergens resulting from cross-contamination of foods. For this reason, reliable and highly sensitive analytical methods are needed to be developed for control and labeling of food ingredients and products. In the present paper we have proposed a new allergen specific sandwich-ELISA for hazelnut operated in optical and electrochemical modes. The ELISA was based on chicken egg yolk antibodies raised against a major hazelnut allergen, Cor a 9. The developed ELISA has a limit of detection in phosphate buffer of 4 ng mL(-1). No significant cross-reactivity with peanut, wheat or other food ingredients has been detected. Extracts of blank control cookies did not show any false positive response and the limit of detection in cookies was estimated to be 0.1 μg of hazelnut protein per g of food (0.1 ppm). The ELISA protocol was successfully adapted to operate in electrochemical mode and it was applied for the detection of hazelnut traces in cookies.