Comparison of Two Fractionation Methods in the Study of Muscle Lipids from Grain- and Grass-finished Beef

Possible differences in composition of fat from grain- and grass-finished beef have been of interest at the University of Tennessee since Meyer et al. (1960) reported the fat of grain-finished beef to be superior in flavor to that of grass-finished beef. In later work the fat from animals of these two types of finish differed chiefly in the proportion of phospholipids and in the degree of saturation of the phospholipids (Cook, 1963; Nutt, 1963).

Observations of other workers also have focused attention on lipid fractions. Early studies showed a correlation between muscle activity and phospholipid content (Bloor, 1927; Bloor and Snider, 1934; Snider, 1936). More recently lipid fractions have been studied in attempts to explain flavor changes in foods (Lea, 1957; Younathan and Watts, 1960; Lee and Mattick, 1961; Hornstein et al., 1961). Results of these studies have implicated phospholipids in flavor deterioration.

In view of the interest in the study of specific fractions, methods of separating phospholipids from non-phosphorus lipids are important. Two general fractionation procedures have been used most extensively: (1) the slurry method described by Murty et al. (1960), and (2) the column method exemplified by the procedure of Hornstein et al. (1961). Both methods have been used in this laboratory but a comparison of their effectiveness had not been made. Therefore, a study was planned for the purpose of making such a comparison and also of obtaining further information concerning the muscle lipids of grain and grass-finished beef. Three different muscles were used on the assumption that they might represent a range with respect to phospholipid content.