Glutaraldehyde Fixation of Casein Micelles for Electron Microscopy

Abstract

Fixation of casein micelles from skimmilk (Bos taurus) for electron microscopy has been compared using osmium tetroxide, formaldehyde and, for the first time, glutaraldehyde. With the latter, a rapid procedure, coupled with a dispersion method, has been developed. Glutaraldehyde appears to preserve micelle structure better than either osmium tetroxide or formaldehyde and eliminates the need for time-consuming centrifugation. The method is easily adaptable to research on concentrated milks and artificial milk systems as well as on fresh skimmilk.Glutaraldehyde-fixed micelles show a range of sizes from 500 to 2,500 Å. Most of the micelles fall in the range of 1,000 to 1,700 Å in diameter, although this range will vary from milk to milk.