Proteomics analysis of milk fat globule membrane enriched materials derived from by-products during different stages of milk-fat processing

By-products produced during milk-fat processing contain abundant milk fat globule membrane (MFGM) and are usually considered as sources of MFGM proteins. However, the technological conditions during cream processing affect the composition/profile of the MFGM proteins and change the functional properties of MFGM proteins. In this paper, the simulative process of industrial manufacture of cream, butter and anhydrous milk fat was done in the lab, five kinds of by-products were collected from different stages (different technical treatments or different fat content) to isolate MFGM enriched material. Proteomics analysis of MFGM enriched materials was performed by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). 357, 429, 323, 578 and 332 proteins were identified in five groups of by-products. Several major MFGM proteins were detected in all samples with the high relative abundance. Samples obtained after phase inversion showed higher protein number and higher concentration of major MFGM proteins compared with centrifuged skimmed milk. Both the number and the concentration in samples collected after phase inversion increased with fat content of cream. GO analysis revealed GTPase activity was the specific molecular function of MFGM proteins in butter serum (BS-1). The MFGM protein profiles also provided novel insights into the individual MFGM product which was rich in certain membrane proteins. Butter serum was the best source for isolating complete MFGM proteins product. This work will facilitate the development of deep processing market for dairy by-products, and provide theoretical reference for the production of MFGM protein products.