Effect of Mechanical Treatment on the Free Fatty Acid Content of Raw Milk

¹ Department of Food Science, University of Wisconsin, Madison 53706

The relative effect of different milking procedures, physical handling, and pumping on lipolytic activity in milk was investigated. Six cows were selected by their stage of lactation from the University of Wisconsin dairy herd. Samples of raw milk were collected daily from individual cows and from each point where physical abuse occurred as milk passed to the bulk tank

Samples were refrigerated rapidly and analyzed to determine concentration of FFA. The method of Deeth and Fitzgerald was used to obtain FFA concentrations initially and after refrigerated storage at 4°C for 24, 48, and 72 h. A milk pump that contained a rotor turning at 3500 rpm was replaced with one turning at 1750 rpm. Analysis of FFA was repeated in individual milk samples. Results show a higher concentration of FFA in milk moved by a pump turning at 3500 rpm. Significantly greater increments of rancidity were observed in these samples after storage. Recommendations are given to minimize lipolysis caused by mechanical abuse on raw milk in farms and plant handling systems.

Key Words: lipolysis • raw milk • free fatty acids

Submitted on December 11, 1989
Accepted on March 7, 1990