Effect of Pasteurization, Freeze-drying and Spray Drying on the Fat Globule and Lipid Profile of Human Milk

Human milk is the ideal food to nourish newborn babies; it contains important nutrients: proteins, carbohydrates, fat, vitamins and minerals, which are needed to provide agood health to the infants. Milk fat provides about 50% of energy to infants and its fatty acids are essential for brain and retina development. Therefore, analysis of the lipid fraction of human milk is an important task, especially when this milk is processed. The objective of this research was to study the effect of pasteurization, freeze-drying and spray drying on some characteristics of human milk fat. The fatty acid profile was analyzed by HPLC and gas chromatography. Fat content, globule size and distribution were measured. The HPLC method for the analysis of fatty acids showed accuracy, precision and linearity in the concentration range studied. Non-significant differences in fat content between the different processes were found; however, there was a decrease of 23% in the fat content of spray dried milk. The fat mean globule size decreased considerably in all treatments, varying from 2138 to 529 nm. The size distribution of fat globules increased during pasteurization and drying from 0.24 in raw milk to 0.78 in pasteurized milk. With respect to the fatty acid profile, we found that human milk samples had an elevated content of palmitic (27%), and oleic (30%) acids and significant variations were observed in the pasteurized samples for oleic and linoleic acid. Preservation processes applied to human milk caused a decrease on the fat globule diameter; the change in size increased the surface area and could improve the bioavailability of the fat components. This is the first report of human milk drying as a preservation method.