Relative Emulsifying Activity of Bovine Serum Albumin and Casein as Assessed by Three Different Methods

The relative emulsifying activities of bovine serum albumin (BSA) and casein as determined by computerized optical microscopy, electron microscopy and spectroturbidimetry at a protein concentration of 0.135 mM (pH 7) and an oil:water (o:w) ratio of 4:6, was compared. Repeated homogenization led to a more homogeneous distribution of dispersed phase globules. BSA stabilized globules became smaller, e.g. the mean globule diameter determined by the different methods decreased from 3.1 μ at an energy input of 7.6 × 10 7 J m −3 to 2.2μ, at 182 × 10 7 J m −3 . Casein stabilized globules became larger with energy input, e.g. mean d vs increased from 5.0μ at 7.6 × 10 7 J m −3 to 5.8μ. at 182 × 10 7 J m −3 indicating structure dependent differences in the emulsifying activity of protein.