The Action of Milk Fat as a Foam Depressant

Abstract

The action of the milk fat in milk as a foam depressant has been discussed in connection with the theories which have been proposed to explain the phenomenon. The consequences of these theories have been investigated experimentally. Contrary to some of the ideas expressed adsorption experiments indicate that the action of milk fat is not due to the removal by the fat of the protein adsorbed at the air/milk serum interface; and surface tension, and superficial viscosity measurements indicate that the action is not attended by any significant changes in the dynamic and static surface tension, or in the superficial viscosity of milk serum. The destructive action of milk fat and other lipoids on foam depends in some way upon the ability of these substances to spread on pure water, and consequently the theories relating to the destructive action of fat on foam which do not take into consideration the importance of spreading, are open to criticism. It has been pointed out that the presence in a thin film of a globule of a substance which will spread may be considered tantamount to the existence of a rupture, and the suggestion has been made that the decrease in foaming power occurring when skim milk is added to milk serum is capable of interpretation on the basis of the equivalence noted between the existence of a rupture, and the presence of a spreading substance in a thin film. Procedures have been described for the measurement of dynamic surface tension, and of an index of superficiual viscosity. © 1935, American Dairy Science Association. All rights reserved.