Changes in milk protein interactions and associated molecular modification resulting from thermal treatments and storage

We investigated protein modifications that occur during short‐ and long‐term storage of raw, pasteurized, and ultra‐high‐temperature processed (UHT) milks using RE‐HPLC and redox proteomics. The RE‐HPLC results show that casein dissociation and whey protein/κ‐casein association occurred in both pasteurized and UHT milk. The extent of protein interactions was more pronounced in UHT milk after storage. The redox proteomics analyses show that primary structural level protein modifications were not correlated to processing type on the of day processing but did occur and increase during storage. Methionine oxidation was the most significant type of oxidative modification in all samples, particularly in the caseins. Methionine oxidation increased in the UHT‐treated milk samples with longer storage times, especially in the micelle‐phase proteins, likely due to the increasing exposure of these proteins as they migrated to the serum phase. Glycated and lactosylated early‐stage Maillard reaction products were also found after heat treatment, particularly in UHT‐treated milk, with the levels of these products maintained and generally increased with increasing storage time.