The casein complexes (casein micelles) of human skim milk were evaluated by electron microscopy. Fourteen samples of human milk were obtained from seven donors whose stage of lactation varied from 1 to 23 months. Compositional and biochemical parameters were measured to evaluate the nature of these samples. For mature human milks, 2-13 months of lactation, average percentage of solids-notfat was found to be 8.32 ± 0.16. Protein compositions of the skim milks were studied by the Coomassie blue dye binding method and by SDS-gel electrophoresis; total protein and casein were found to be 0.62 ± 0.18 and 0.29 ± 0.02 percent, respectively. The lysozyme and lactoferrin contents were also determined. The total casein of the skim milks appeared to increase slightly as lactation progressed; an exception occurred in milks obtained from one donor at 22 and 23 months postpartum which exhibited decreased casein and elevated l ysozyme and lactoferrin contents . The overall morphology of the casein micelles was evaluated by electron microscopy using platinum shadowing, negative staining, and thin sectioning methods. Platinum shadowing was largely unsuccessful, but negative staining showed a discrete substructure for human casein micelles. Average corrected diameters of q.3. 0 nm from the area and 47.5 nm from circumference measurements were obtained from analysis of fixed and pelleted human milk micelles.
Carroll, Robert J.; Basch, Jay J.; Phillips, John G.; and Farrell, Harold M. Jr.
"Ultrastructural and Biochemical Investigations of Mature Human Milk,"
2, Article 15.
Available at: http://digitalcommons.usu.edu/foodmicrostructure/vol4/iss2/15