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

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 alpha-serum, beta-serum, and buttermilk powder (BMP). Caseins were the dominant proteins in the MFGM fractions isolated from BMP and buttermilk, whereas fractions from alpha- and beta-serum contained higher amounts of membrane proteins. The XO content and activity was >70-fold and >700-fold higher in alpha- and beta-serum samples, respectively, compared with the BMP fraction. The Eh values of the recombined emulsions were highest for alpha-serum (196 mV), and beta-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. (C) 2016 Elsevier Ltd. All rights reserved.