Surface-active substances applied to the surface of whole milk may either bring fat globules, clumps, lenses and patches on to this surface, or sweep the surface clean of these fat forms.
In the homologous series of monohydric aliphatic alcohols, methyl and ethyl alcohols show a moderate rising action, whereas the other members from n-propyl alcohol to n-decyl alcohol are strongly active. There is only a slight difference in the activity of primary, secondary and tertiary butyl alcohols.
Ageing of milk slightly promotes the rising of fat globules on to the surface under the action of ethyl to n-amyl alcohols.
Alcohols, beginning with n-propyl alcohol, bring fat globules to the surface of milk much more strongly than does mechanical disturbance of the surface by touching with a platinum ring.
Glycerol, due to its three hydroxyl groups and a weak hydrophobic residue, is almost inactive, monobutyrin is strongly active in bringing the fat globules to the surface, while tributyrin sweeps the surface clean.
Spans and Tweens, sorbitan and polyoxyethylene sorbitan esters of higher fatty acids sweep the milk surface clean.
The author wishes to thank Mr G. Loftus Hills, Officer-in-Charge of the Dairy Research Section, C.S.I.R.O., Melbourne, for helpful discussion, and the Atlas Powder Company, Wilmington, Del., U.S.A., as well as its Australian representatives, Chemical Materials Pty. Ltd., Glebe, N.S.W., and Hardie Trading Ltd., Melbourne, for samples of Spans and Tweens.