ELECTROACOUSTIC DETERMINATION OF SIZE AND ZETA-POTENTIAL OF CASEIN MICELLES IN SKIM MILK

Measurements of the zeta potential and particle size of ca sein micell es in skim milk suspensions at natural and lower pH have been made usi ng the technique of electroacoustics. This technique requires no dilut ion or change of environment of the casein micelles. The zeta potentia l obtained at natural pH for a commercial skim milk suspension was -18 mV; it became less negative with decreasing pH. The median particle s ize observed at natural pH for a commercial skim milk suspension was 0 .2 mu m, in good agreement with previously reported values. The partic le size increased as the pH was decreased.