Enhanced quantitation of egg allergen in foods using incurred standards and antibodies against processed egg in a model ELISA.

Underestimation of egg allergen from processed foods prompted the evaluation of critical Enzyme-Linked Immunosorbent Assay (ELISA) parameters: (1) extraction of egg proteins from a processed matrix; (2) use of anti-heat processed egg antibodies (Abs) on detectability of modified proteins, and (3) utilization of incurred material as standards. The relative affinity of two combinations of raw (R), boiled (B) and fried (F) Abs to unprocessed/processed egg proteins with or without matrix was determined from antibody (Ab) binding curves. In ELISAs using RBF-Abs and BF-Abs, denaturing buffer, and incurred standards, the Limit of Detection (LOD) and Limit of Quantitation (LOQ) were 0.47 and 0.25; and 1.58 and 0.85, respectively, and the linear range was 0-24 µg g-1 egg protein. The recoveries of egg protein from cookies, cereal bar, and muffin (incurred levels 4.8-48 µg g-1) with the developed ELISAs were in an acceptable range (50-130%). These ELISAs consistently detected more declared/undeclared egg proteins in market samples compared to assays using PBS for extraction. Overall, better assay performance was observed using BF-Abs. An ELISA combining anti-processed egg Abs, denaturing buffer, and incurred standards promises improved quantitation of egg proteins in processed foods.