The impact of cream churning conditions on xanthine oxidase activity and oxidation–reduction potential in model emulsion systems

Six types of milk fat globule membrane (MFGM) fractions were isolated from fresh raw cream using various churning conditions at different temperature (10, 15 or 20 °C) and pH values (5.5 or 6.6) and characterised for protein composition, xanthine oxidase (XO) content and activity, and oxidation–reduction potential (Eh). A greater proportion of non-membrane proteins was found at higher temperatures and higher cream pH, and the XO content decreased significantly under these conditions. XO activity was greater at lower temperatures and pH, yielding a more positive Eh value for the emulsions. Storage at 4 °C for 14 d significantly reduced the Eh of the emulsions to between −320 mV and −580 mV for low pH/low temperature, and high pH/high temperature emulsions, respectively. This study suggests that it is possible to obtain MFGM fractions with specific Eh reducing ability by altering churning conditions.