Purpose: The objective of this study was to evaluate a new commercially available monoclonal antibody-based direct sandwich enzyme-linked immunosorbent assay (ELISA) kit for cashew detection.
Methods: Cashew nut seeds and food ingredients were purchased from local grocery stores and the ELISA kits were purchased from BioFront Technologies (Tallahassee, FL). Whole cashew nut seeds were subjected to autoclaving (121°C, 15 psi, 15, 30 min), blanching (100°C, 5, 10 min), frying (191°C, 1 min), microwaving (500, 1000 W, 3 min), and roasting (140°C, 30 min; 168, 177°C, 12 min). Soluble proteins were extracted in the provided extraction buffer (flour-to-buffer ratio 1:10 w/v) at 60°C for 10 min and quantified by the Bradford method. Samples were subsequently analyzed by ELISA.
Results: The ELISA was sensitive (limit of detection: 0.07 ± 0.02 ppm, linear detection range: 0.2 - 20.0 ppm), reproducible (intra- and inter-assay variability < 15% CV), and rapid (post-extraction testing time: ~40 min). The target antigen was detected in the processed samples. Compared to the unprocessed control, percentage cashew recovery was 89.0 - 99.2% for all processed cashew nuts except those autoclaved for 30 min (44.2 ± 0.9% recovery, P ≤ 0.05). At 10,000 ppm, no cross-reactivity was observed in 120 tested food matrices except pistachio seeds (signal equivalent to 0.7 ± 0.1 ppm cashew). The signal registered by pistachio was eliminated at 1000 ppm.
Significance: The results suggest that under the test conditions, the ELISA was specific, sensitive, and robust for cashew detection.