Determination of Nε-carboxymethyllysine in heated milk products by immunochemical methods

Nε-Carboxymethyllysine (CML) is an important Maillard product which is formed in vivo and during food processing and heating, and which can therefore be used as a marker for heat damage of foodstuffs. A competitive enzyme-linked immunosorbent assay (ELISA) was developed to detect CML modifications on proteins. CML protein was synthesized and anti-CML antiserum was prepared, which recognized CML modifications specifically on CML proteins and proteins which were incubated with various carbohydrates. Heated milk and milk powder samples could be directly tested by ELISA without further clean-up procedures and the CML contents were determined in relation to reaction time and heating conditions. Positive results were confirmed by SDS-PAGE/immunoblotting using the same antiserum. ELISA proved to be a fast, specific, and easy-to-handle method to evaluate CML formation in heated milk products. Additionally, SDS-PAGE/immunoblotting can be helpful to detect CML also in insoluble food proteins. © Springer-Verlag 1999.