Inhibitory Effects of Fatty Acids, Chelating Agents, and other Substances on Rennet Clotting of Skim Milk

Abstract

In vitro studies were on inhibition of rennet-casein clotting by free fatty acids, chelating agents, and other substances as affected by pH and added calcium++. At .4% (volume/volume), pH 6.1, propionic, butyric, caproic, and heptanoic acids were relatively ineffective in inhibiting clotting of reconstituted skim milk powder (10%, weight/volume); caprylic, myrstic, oleic, linoleic, and linolenic acids were highly inhibitory; and capric, lauric, and pelargonic acids completely prevented coagulation. Clotting at pH 6.1 also was prevented by 15 mM citrate, 5 mM phytic acid, 10 mM ethylenediaminetetraacetic acid, 100 mM formaldehyde, and 5 mM sodium lauryl sulfate. Lowering pH below 6.1 and adding 20 mM calcium++ restored clotting and curd firmness to varying degrees for all agents. In studies on the role of stomach clots on the performance of young calves involving use of clot-preventive agents in milk replacer, the free fatty acids and other agents used here likely would not be useful because even small reductions in pH below 6.1, as occur in the abomasum soon after feeding, markedly reduce their anticlotting activity. © 1983, American Dairy Science Association. All rights reserved.