Rennet coagulation properties of milk in the presence of MFGM fragments isolated from raw - and pasteurised-cream buttermilk

Milk fat globule membrane (MFGM) fragments were isolated from raw- and pasteurised-cream buttermilks to determine their impact on the rennet coagulation properties of milk. These MFGM fragments were recovered by ultracentrifugation after casein micelle dissociation using sodium citrate. This procedure was also applied to raw skim milk as a control. More protein was recovered from the two types of buttermilk than from the skim milk upon centrifugation. This protein was mostly MFGM, but significant amounts of caseins and whey proteins were also recovered. This suggests that the churning of cream induces changes in these proteins, favouring their sedimentation upon ultracentrifugation. The isolated material was suspended in reconstituted skim milk, and rennet coagulation kinetics and gel contraction capacity were measured. The MFGM fragments isolated from buttermilk impaired rennet gel formation and reduced gel contraction capacity, but these effects were not related to the cream pasteurisation treatment.