Proteomics and surface free fatty acid analysis of milk fat globules in spray- and freeze-dried bovine, goat, and horse milk powders

Changes in the structure and composition of milk fat globules in spray- and freeze-dried milk powders have recently garnered notable attention. This study investigated changes in milk fat globular membrane (MFGM) proteins from bovine, goat, and horse milk powders, both spray- and freeze-dried, using a label-free proteomic approach, and quantified surface free fatty acids and their composition using GC. The results showed that several proteins, including α_S2-CN and β-LG, increased, whereas fibrinogen α and β chain and mucin-1 decreased in the MFGM fractions of the studied spray-dried milk powders. Additionally, lactoperoxidase and polymeric immunoglobulin receptor levels were elevated in the studied freeze-dried milk powders. Several proteins exhibited variations in both dried milk powders depending on the species; of these, nucleobindin-1, complement C3, and sulfhydryl oxidase were increased in spray-dried bovine and goat milk powders, and lactoferrin was increased in freeze-dried horse milk powder, compared with their raw milk counterparts. Conversely, butyrophilin subfamily 1 member A1 and xanthine dehydrogenase/oxidase were decreased in spray-dried bovine and goat milk powders, S100 calcium-binding protein and aldehyde dehydrogenase were decreased in freeze-dried bovine and goat milk powders, and mucin-4 and paraoxonase were decreased in horse milk powder. Additionally, spray-dried milk powders had lower surface free fatty acid contents than freeze-dried milk powders. The findings underscore that drying methods exert varied effects on MFGM components of the studied milk sources, thereby providing a valuable reference for improving the nutritional quality of dried dairy products.