Size Distribution and Solvation of Casein Micelles in Milk Containing αs1-Casein A

We compared the size distribution and solvation of micelles in skim milk from a cow homozygous for oct,-casein A with the properties of micelles from pooled skim milk. Hydrodynamic radii of the micelles were measured by inelastic laser light scattering, and a cumulative distribution curve of the weight fraction of micelles with radii less than or equal to a given value was eonstnlcted. Micelle solvations were measured from voluminosities measured viscometrically. The distribution of mieelle sizes is strikingly different in ~.~l-easein A milk and in pooled milk, with the former having both much larger micelles and a greater proportion of small micelles. We found no significant differences in solvation of micelles from ~-casein A or pooled skim milks.