Determination of N-epsilon-carboxymethyllysine in heated milk products by immunochemical methods

N-epsilon-Carboxymethyllysine (CML) is an important Maillard product which is formed in vivo and during food processing and heating, and which can the refore be used as a marker for heat damage of foodstuffs. A competitive enz yme-linked immunosorbent assay (ELISA) was developed to detect CML modifica tions on proteins. CML protein was synthesized and anti-CML antiserum was p repared, which recognized CML modifications specifically on CML proteins an d proteins which were incubated with various carbohydrates. Heated milk and milk powder samples could be directly tested by ELISA without further clea n-up procedures and the CML contents were determined in relation to reactio n time and heating conditions. Positive results were confirmed by SDS-PAGE/ immunoblotting using the same antiserum. ELISA. proved to be a fast, specif ic, and easy-to-handle method to evaluate CML formation in heated milk prod ucts. Additionally, SDS-PAGE/immunoblotting can be helpful to detect CML al so in insoluble food proteins.