Characterisation and Stability During Storage of Liposomes Made of Muscle Phospholipids

Liposomes can be used as model systems to study the oxidation of phospholipids of meat products, providing an understanding of their characteristics and stability. Liposomes made of muscle phospholipids were prepared using three methods. They exist in multilamellar vesicles, small unilamellar vesicles and large unilamellar vesicles, as seen by electron microscopy of freeze-fractured samples. Fatty acid and class compositions of liposomes and phospholipid extracts were similar. In small unilamellar vesicles and large unilamellar vesicles, conjugated dienes and thiobarbituric acid values (TBA-rs) were slightly higher than in multilamellar vesicles and phospholipid extracts, but they remained at a very low level. During storage at 4° C in air, polyunsaturated fatty acids, the phosphatidyl ethanolamine/phosphatidyl choline ratio, conjugated dienes and TBA-rs were stable for at least 7 d. Turbidity of small unilamellar vesicles and large unilamellar vesicles increased slightly with time, indicating changes in the size distribution of liposomes. Liposomes can therefore be prepared from muscle phospholipids with no major deterioration in lipids. Furthermore, their stability during short term storage (3 d) is good. The method chosen to prepare liposomes should take into account the physical structure of liposomes, which can interfere with further experiments.