Appearance and Size of Micelles from Bovine Milk

Abstract

Electron micrographs of a number of milks from individual cows were prepared by a replica technique and average micelle diameters determined by appropriate calculations based on visual counts of the number of micelles in various size ranges. The milks were analyzed for several inorganic constituents and proteins and their stability at 40[degree]C determined. The major factors influencing micelle size were total soluble Ca and K-casein (as a percent of total casein). Citrate concentration as related to micelle diameter, may be an indirect effect, as citrate was the major factor influencing the concentration of soluble Ca. Ionic Ca was not significantly related to average micelle diameter. Heat stability (140[degree]C) was not significantly related to average micelle diameter. The [beta]-casein which dissolved from micelles of cooled milk probably did not re-enter the micelles as the milk was rewarmed to 35[degree]C but merely deposited on the surface of the micelles.