Impact of different milk fat globule membrane preparations on protein composition, xanthine oxidase activity, and redox potential

Abstract The protein composition, redox potential (E h ), and xanthine oxidase (XO) content and activity were determined for anhydrous milk fat emulsions containing milk fat globule membrane (MFGM) fractions derived from either buttermilk or commercial sources of bovine α-serum, β-serum, and buttermilk powder (BMP). Caseins were the dominant proteins in the MFGM fractions isolated from BMP and buttermilk, whereas fractions from α- and β-serum contained higher amounts of membrane proteins. The XO content and activity was >70-fold and >700-fold higher in α- and β-serum samples, respectively, compared with the BMP fraction. The E h values of the recombined emulsions were highest for α-serum (196 mV), and β-serum (169 mV), followed by BMP (131 mV). These positive values contrasted with the highly negative E h of the buttermilk emulsion (−580 mV). This study demonstrates how milk-processing methods can alter the composition and functionality of the MFGM.