Detection of hen’s egg white lysozyme in food: Comparison between a sensitive HPLC and a commercial ELISA method

Recently some cases described allergic reactions to undeclared lysozyme present in foods. In order to protect the allergic consumer, a better control is needed based on reliable and specific detection and quantification methods. The two currently used methods, a commercially available enzyme-linked immunosorbent assay (ELISA) for egg white allergens and a liquid chromatographic method, were compared. Despite the technical specifications of the ELISA kit, ensuring quantitative analysis of lysozyme in absence of other egg white proteins, no reliable quantitative and even qualitative data could be obtained which contrasted with the capabilities of the instrumental technique. A more elaborated evaluation of the methods on spiked samples identified the causes of the observed discrepancies. It was shown that next to a poor sensitivity of the ELISA kit also an insufficient lysozyme extraction and a co-extraction of interfering substances were the causes of the anomalies observed during application of the immunochemical method.