Detection of egg and milk residues on working surfaces by ELISA and lateral flow immunoassay tests

•Optimization of a procedure for allergen control on surfaces by combination of a swabbing method and two immunochemical tests.•Selection of swab material and extraction buffers influence the recovery of egg and milk residues.•Swabbing method should be adapted to the kind of surface and the detection method.•Quantitative ELISA method can be used for the validation of cleaning procedures in food industry facilities.•Qualitative lateral flow test is an easy and suitable method for routine verification of cleaning effectiveness.

In the last few years awareness for allergen management has increased among operators in the food chain. Since a small quantity of allergenic food can trigger an allergic reaction, accurate information in food product labels is essential for people who suffer from food allergy. A key point to reduce the risk of uncontrolled allergen contamination is to implement a strict and validated cleaning process. In this work a sampling method based on swabbing has been optimized with two analytical methods (ELISA and lateral flow tests) for milk and egg analysis on surfaces. Swab material, extraction buffer composition, temperature, time for recovery and the quantity of the allergen residue on the surfaces have been evaluated and a specific procedure was proposed. The new method has demonstrated a good performance to recover egg or milk proteins from two typical working surfaces (stainless steel or Formica). Egg and milk powder were detected by ELISA at a level as low as 0.04 and 0.2 μg, respectively. However, the detection level with lateral flow tests rose to 0.07 μg for egg powder and 0.6 μg for milk, depending on the kind of surface. On average, repeatability of swabbing method ranged from 18 to 32%. Both methods could be applied for validation the cleaning processes and for a routine verification after cleaning.