The diameter of milk fat globules ranges from 0.1 to 15 $\mu\text{m}$, with the average fat globule diameter in cow milk being approximately 3.5 to 4.0 $\mu\text{m}$. In buffalo milk, the average size is larger (~4.5 to 5.5 $\mu\text{m}$).

Human breast milk contains the highest lactose concentration among common mammals, averaging around 7.0% to 7.2%. Cow milk contains ~4.6-4.8%, camel milk ~4.4-4.8%, and reindeer milk ~2.5% lactose.

Biochemical basis of colostrum thermal coagulation:
(A), (B), (D) Electrolytes and fat play secondary roles in destabilization.
(C) First-milking bovine colostrum contains exceptionally high levels of total protein ($14\text{ to }18\%$, compared to ~3.3% in mature milk), driven primarily by huge concentrations of heat-labile whey proteins, especially Immunoglobulins ($IgG_1$, representing up to $80\%$ of colostral whey protein). Immunoglobulins denature and unfold readily at temperatures above $60\text{--}65^\circ\text{C}$, exposing hydrophobic residues that cross-link into a rigid thermal coagulum. This extreme protein load causes colostrum to curdle instantaneously upon heating.