Characterisation and stability during storage of liposomes made of muscle phospholipids

Liposomes can be used as model systems to study the oxidation of phospholip ids of meat products, providing an understanding of their characteristics a nd stability. Liposomes made of muscle phospholipids were prepared using th ree methods. They exist in multilamellar vesicles, small unilamellar vesicl es and large unilamellar vesicles, as seen by electron microscopy of freeze -fractured samples. Fatty acid and class compositions of liposomes and phos pholipid extracts were Similar. In small unilamellar vesicles and large uni lamellar vesicles, conjugated dienes and thiobarbituric acid values (TBA-rs ) were slightly higher than in multilamellar vesicles and phospholipid extr acts, but they remained at a very low level. During storage at 4 degrees C in air, polyunsaturated fatty acids, the phosphatidyl ethanolamine/phosphat idyl choline ratio, conjugated dienes and TBA-rs were stable for at least 7 d Turbidity of small unilamellar vesicles and large unilamellar vesicles i ncreased slightly with time, indicating changes in the size distribution of liposomes. Liposomes can therefore be prepared from muscle phospholipids w ith no major deterioration in lipids. Furthermore, their stability during s hort term storage (3, d) is good. The method chosen to prepare liposomes sh ould take into account the physical structure of liposomes, which can inter fere with further experiments. (C) 1999 Academic Press.