Infant formula (IF) is the recommended substitute when breastfeeding is not possible, but studies have demonstrated compromised health of IF fed infants when compared to breastfed infants. Proteins are essential for healthy infant development, but the composition of IF makes it prone to processinduced protein modifications, which may reduce the protein quality of the final product. In the present PhD study, the impact of unit operations and protein ingredient processing on protein quality was investigated by characterising structural changes, covering protein denaturation and aggregation, and formation of Maillard reaction products. The formation pathways of Maillard reaction products
are complex and their potential health implications are a contentious subject. Therefore, numerous Maillard reaction products were quantified, where the presence of α-dicarbonyls in particular, reinforced the importance of considering the reaction in its entirety.
Liquid IF is commonly treated by indirect ultra high temperature (UHT), but was found to promote structural protein modifications when compared to direct UHT. Differences did not converge during storage at 40 °C for 180 days, illustrating the applicability of direct UHT for improved protein quality.
Several processing steps are included in manufacturing of whey protein concentrate (WPC) that can impair the protein quality, which is problematic since it is the commonly used protein ingredient in IF. Fractionation based processes have recently enabled production of serum protein concentrate (SPC), which is a minimally processed whey protein ingredient. The impact of whey protein ingredient processing was investigated in powdered IF, where protein modifications were reduced by substituting WPC with SPC. However, ingredient differences were generally overshadowed by subsequent protein modifications, formed during powder manufacturing, and process optimisation may have a more significant outcome on the protein quality of powdered IF.
Accumulation of Maillard reaction products and structural changes in a powdered formula and IF model samples were affected differently by unit operations, which demonstrated the complexity of process-induced protein modifications during powder manufacturing. Investigation of dry blending of lactose in a model system demonstrated that partial dry blending of lactose could have commercial relevance in reducing protein modifications in powdered IF. More surprisingly, observations implied that process optimisation of the lactose ingredient could be an innovative approach for improving protein quality of powdered IF.