Distribution of lipids in various fractions of cow milk

Abstract

The distribution of lipids in various milk fractions (cream, skim milk, casein, whey, and separator slime) was studied. Petroleum ether and chloroform-methanol (2 to 1) were used successively as solvents. The petroleum ether fraction is referred to as "free" lipid and the chloroform-methanol fraction as "bound" lipid. Neutral lipids were found in both the free and the bound fractions in milk. Phospholipids were found in the bound fraction only. The composition of the glycerides was determined by thin layer chromatography. The diglyceride and monoglyceride content of the bound neutral lipid fraction was much higher than that of the free neutral lipid fraction. No significant difference in the composition of the phospholipids was observed among the various milk fractions.

Composition of the bound lipids in caseins and in ripening cheeses

“…Table 1 shows the amounts of free and bound neutral lipids and phospholipids found in the casein preparations. The data for iso-electric casein agree with those found by Cerbulis (1967). a-Casein appeared to have the highest content of bound phospholipids.…”

“…Free lipids were extracted from the freezedried caseins with petroleum ether and the bound lipids with chloroform-methanol (2:1, v/v) as described by Cerbulis (1967). From the bound lipid fraction some nonlipid contaminants were removed as described by Folch, Lees & Sloane Stanley (1957); the lipid mixture was then separated into neutral lipids and phospholipids by silicic acid chromatography (Abramson & Blecher, 1965).…”

“…and Cerbulis (1967) found that the lipids associated with acid-precipitated casein are not completely extractable by any single solvent. Even a chloroform-methanol (2:1) mixture did not remove all casein-bound lipids, some of which were removed only by saponification.…”

“…In the bound phospholipid fraction of 3 cheeses the same phospholipids were found together with 1 new unidentified spot. Cerbulis & Zittle (1965) and Cerbulis (1967) found that the lipids associated with acid-precipitated casein are not completely extractable by any single solvent. Even a chloroform-methanol (2:1) mixture did not remove all casein-bound lipids, some of which were removed only by saponification.…”

“…Even a chloroform-methanol (2:1) mixture did not remove all casein-bound lipids, some of which were removed only by saponification. Cerbulis (1967) studied the distribution of lipids in casein, skim-milk, whey, cream and separator slime, and defines as 'free lipid' the fraction extractable with petroleum ether, and as 'bound lipid' the fraction extractable with chloroform-methanol mixture. Neutral lipids were found both free and bound, while phospholipids were found only in the 'bound' fraction.…”