A comparison of the phospholipid content of conventional milk with that of organic milk and milk rich in conjugated linoleic acid (CLA) has shown relative differences, as well as some similarities, between all three type of milk. The work was conducted by T. Ferreiro, L. Gayoso, J.L. Rodríguez-Otero of the Instituto de Investigación y Análisis de Alimentos in Spain.
The membrane enclosing the fat globules of milk is composed, in part, of phospholipids, which have properties of interest for the development of so-called functional foods and technologically novel ingredients. They include phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylcholine (PC), phosphatidylserine (PS), and the sphingophospholipid sphingomyelin (SM).
Milk from organically managed cows contains higher levels of vitamins, antioxidants and unsaturated fatty acids than conventionally produced milk, but no work had been done in regard to an analogous comparisons of major phospholipid contents.
In addition, the use of polyunsaturated-lipid-rich feed supplement (extruded linseed) has been reported to increase the phospholipid content of milk. Because supplementation with linseed and increased unsaturated fatty acid content are the main dietary modifications used for production of CLA-rich milk, the researchers investigated whether these modifications would lead to this milk having higher phospholipid content.
For their study, the researchers used HPLC with evaporative light scattering detection to determine PE, PI, PC, PS and SM contents in 16 samples of organic milk and eight samples of CLA-rich milk, in each case together with matching reference samples of conventionally produced milk taken on the same days and in the same geographical areas as the organic and CLA-rich samples.
They found that compared with conventional milk and milk fat, organic milk and milk fat had significantly higher levels of all the phospholipids studied. They said this was attributable to the differences between the two systems of milk production, among which the most influential are probably differences in diet and physical exercise.
The CLA-rich milk fat had significantly higher levels of PI, PS, and PC than conventional milk fat, which they said was also attributed to dietary differences. Rations for CLA-rich milk production included linseed supplement and contained less maize meal than conventional rations and a greater proportion of unsaturated fatty acids and salts.
The relative proportions of the phospholipids studied were similar in all 3 types of milk, descending in the order PE > (PC, SM) > PS > PI, with PC being slightly more abundant than SM in organic milk and vice versa in CLA-rich milk, the researchers found.
January 2015 JDS Volume 98, Issue 1