Sphingomyelin from milk – characterization of liquid crystalline, liposome and emulsion properties

• The properties of sphingomyelin obtained from bovine milk were investigated. In particular, the properties of liposomes and emulsions prepared from the sphingomyelin, as well as the liquid crystalline behaviour, were investigated and compared to those of related phosphatidylcholine systems. Like sphingomyelins from other sources, sphingomyelin from milk contains a large fraction of long and saturated acyl groups, which results in a high (35-82°C, depending on the lipid concentration) gel-to-liquid crystal transition temperature (Tc). At high sphingomyelin concentrations, a lamellar phase forms above Tc, while below Tc, a swelling gel phase is obtained. The gel phase swells to about 20 wt% water, whereas above Tc, the swelling continues to about 40 wt% water. The limiting areas per molecule are 51 and 68 Å2 below and above Tc, respectively. Sphingomyelin from milk forms liposomes readily in the presence of cholesterol. The liposomes formed have a diameter of about 100 nm, and are stable even at 0.1 M NaCl or HCl. Materials entrapped in the liposomes are released rather slowly (typically 40 % over 5 h). A comparison shows that the sphingomyelin liposomes behave similarly to those formed by phosphatidylcholine systems. Furthermore, sphingomyelin from milk forms stable o/w emulsions with soy bean oil. The size of the emulsion droplets obtained was about 200 nm. Both the size of the emulsion droplets and its dependence on electrolyte addition correlate closely with those of emulsions formed by the corresponding phosphatidylcholine system. Therefore, it is possible to use sphingomyelin as an alternative for saturated phosphatidylcholines, which may be advantageous for oral and dermal pharmaceutical applications, as well as in cosmetics.

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