Modifications of milk constituents during processing: A preliminary benchmarking study

Lipid and protein components of infant formulas can be subjected to modification during product manufacturing. In this study, protein and lipid modifications of several infant formulas, as well as pasteurized and UHT milk samples were evaluated. The levels of secondary lipid oxidation products (malondialdehyde and hexanal), proteins modified by early (furosine, measurement of protein glycation) and advanced (carboxymethyllysine) Maillard reactions, and oxidized and cross-linked proteins (protein carbonyls, dityrosine, lysinoalanine) were measured. Both lipid oxidation and protein modifications were affected by the processing conditions, but no correlation was observed. Therefore, it is of prime importance to monitor several markers of these modification pathways to better assess the heat treatments. Hydrolyzed proteins from hypoallergenic formulas were shown to be particularly sensitive to oxidative modifications. Further studies on well-defined systems (i.e., precise product composition and industrial treatments) are required to better understand the relationships between lipid oxidation and protein modification.