Conformational changes of infant formula proteins: effect of whey protein composition and processing step

This work investigated the cumulative effect of infant milk formula (IMF) processing steps on protein conformation. Model systems were prepared with varying β-Lactoglobulin (β-Lg): α-Lactalbumin (α-Lac): Lactoferrin (Lf): Osteopontin (OPN) ratios: FC (69.6 : 27.9: 2.1 : 0.4), F1 (39.6 : 57.9: 2.1 : 0.4), and F2 (0 : 57.4: 39.9 : 2.7). Protein structural changes were monitored by intrinsic fluorescence, electrophoresis, and available lysine. Whey protein (WP) composition influenced the extent, type, and stoichiometry of protein aggregation. Densitometric analysis revealed that FC, F1, and F2 retained 20.5 ± 2.8 %, 30.2 ± 6.7 %, and 54.8 ± 3.7 % of the native-like whey protein, respectively. Across all formulations, the pasteurization stage held the greatest influence in aggregate formation. Homogenization effects appear to be independent of WP composition. Fluorescence intensity data showed compositional dependence during pasteurization, evaporation, and to a lesser extent, spray drying. Finally, compositional differences between IMFs affected drying-induced lysine glycation, with F2 showing the greatest rate of lactosylation (23.5 %) presumably because of Lf-induced casein dissociation. These findings highlight the interplay between processing steps and IMF composition as drivers of protein conformation.