Purpose: The objective of this study was to assess the applicability of a commercially available monoclonal antibody-based direct sandwich enzyme-linked immunosorbent assay (ELISA) kit to detect cashew in selected foods.
Methods: ELISA kits were purchased from BioFront Technologies (Tallahassee, FL). Cashew nut seeds, food ingredients, and commercial samples were purchased from local grocery stores. Full fat flours were extracted in kit-provided extraction buffer for 10 min at 60°C (flour-to-buffer ratio of 1:10 w/v) and soluble protein content was determined using the Bradford method. Immunoreactivity of the samples was assessed using the ELISA kit procedure.
Results: Among the 25 tested commercial samples, with and without declared cashew, no false positive or false negative results were obtained by the assay. The percentage recovery for 10 ppm cashew spiked ice cream, dark chocolate, milk chocolate, white chocolate, cereal, corn flake, sponge cake, and sugar cookie was 92.8 ± 3.6%, 66.1 ± 7.5%, 83.7 ± 4.4%, 87.7 ± 3.4%, 93.1 ± 1.5%, 89.5 ± 2.2%, 88.4 ± 4.4%, and 98.7 ± 1.3%, respectively. In case of dark chocolate, addition of 5% non-fat dry milk in the extraction buffer significantly (P ≤ 0.05) improved cashew recovery (66.1 ± 7.5% to 86.0 ± 7.8%). The recovery range for incurred cashew (0.5, 1, 2, and 5%) in the laboratory prepared sponge cake, sugar cookie, and corn flake was 87-118%.
Significance: The tested ELISA kit was able to rapidly detect cashew in the tested foods.