Changes in bioactive milk serum proteins during milk powder processing.

This study mainly investigated changes in milk serum proteins by simulating the industrial processing of whole milk powder using a label-free proteomic approach. A total of 391 proteins were identified, 89 of which were quantified in all groups. Compared with raw milk, the milk subjected to the heating pasteurization process showed significantly decreased the serum protein profile, whereas that subjected to vacuum concentration and spray-drying showed minimal changes. The LC-MS/MS results were further confirmed by determining the activity of bioactive xanthine oxidase and retention of lactoferrin and immunoglobulins. The data showed that 70%-85% of lactoferrin and immunoglobulins were retained in vacuum-concentrated or spray-dried milk but were hardly identifiable in heat-pasteurized milk or whole milk powders. These findings indicate the need for improving the current milk powder-manufacturing techniques to allow the retention of active milk proteins.