Assessment of protein glycation markers in infant formulas

The typical formulation of infant formulas (IF) may enhance damage of proteins during spray drying or sterilization. Lactose reacts with amino groups of proteins resulting in the formation of lactulosyllysine (LL). The latter is further degraded to give advanced glycation end-products (AGEs). Furthermore, oxidation reactions, which are catalyzed by iron can further promote AGE formation. In this study, six parameters for protein modification were measured for 41 commercially available IF samples: lysine blockage, tryptophan degradation and LL formation by HPLC, the AGEs N-epsilon-carboxymethyllysine (CML) and oxalic acid monoalkylamide (OMA) by ELISA. The FAST index was used as a rapid method for monitoring AGEs. IF showed increased lysine loss (6-fold), LL formation (2-3-fold) and AGEs levels (3-5 times) (CML, OMA, and FAST index) compared to similarly treated cow's milk, indicating more severe protein modifications in the former. Further studies on the technological processes are required to minimize heat-induced damage of IF during manufacturing. (C) 2004 Elsevier Ltd. All rights reserved.