Trace amounts of cashew
nut protein can provoke severe
allergic reactions in sensitive patients. Consequently, commercial food processors and regulatory agencies must be vigilant to prevent cashew nut cross-contamination among foods and ensure proper labeling. Toward this end, we have developed a sandwich
enzyme-linked
immunosorbent (ELISA) to detect the predominant cashew
protein fraction (anacardein or cashew major
protein,
CMP) that can be extracted in aqueous
buffer from food matrixes.
Protein G-purified goat antiwhole cashew extract
IgG and rabbit anti-
CMP IgG were used as capture and secondary
antibodies, respectively. Immunoadsorption against several nut and seed
proteins significantly minimized the inherent cross-reactivity of these
reagents. Food samples spiked with cashew flour and
CMP were extracted and tested in a sandwich ELISA where standard curves were based on reactivity with
CMP. The assay was optimized to detect as little as 20 ng/mL (0.02 ppm) of
CMP and was successfully used to quantify
CMP, and thus cashew, in various food matrixes.