Development and Validation of Lateral-Flow Devices for Detection of Tree Nuts and Peanuts

Introduction: Allergies to tree nuts and peanuts are relatively common, with a combined prevalence of 1.5 - 2.5%. The symptoms of allergies to nuts can range in intensity but frequently manifest as a severe, life-threatening reaction termed anaphylaxis. Accordingly, regulatory agencies in Canada and the USA require food labels to clearly indicate tree nut and peanut content so as to alert consumers of potential allergy risks. Observance and enforcement of these labeling laws necessitate the use of antibody-based immunoassays that can detect nut residues in a variety of foods. 

Purpose: To develop and validate a panel of LFDs that can rapidly detect trace tree nut and peanut residues in under 20 min.

Methods: Total protein extracts from raw and roasted (12 min at 180°C) nuts were prepared using a TRIS buffered, 200 mM NaCl, pH 7.2 extraction solution and then used to raise pAbs in goats. IgG was purified from plasma using protein G columns/AKTA Prime FPLC and then applied to lateral flow immuno-chromatographic assay development. In parallel, a proprietary sample extraction buffer was developed to enable rapid and highly sensitive operation of each LFD test.

Results: LFDs were developed for detection of residues derived from peanut, hazelnut, pine nut, brazil nut, cashew nut, pistachio nut, coconut, almond, macadamia nut, and walnut/pecan. Each nut LFD demonstrated a sensitivity of 0.1 µg/swab and 1.0 µg/ml for foods. Specificity analysis revealed no cross-reactivity with common commodities, and minimal cross-reactivity between different nut types, with the exception of cashew and pistachio which cross-reacted with each other. 

Significance: A complete testing panel of LFDs that can rapidly detect tree nut and peanut residues in under 20 min should aid food manufacturers and regulatory entities in monitoring for nut residues.