Abstract
Structural stability of lecithin liposomes during freeze-thawing was studied by investigating their freezing behavior and effects of ice nucleators. DSC cooling traces of the liposome suspension showed exotherms due to the freezing of extra- and intraliposomal solutions. The exotherm due to freezing of the intraliposomal solution hardly changed even if freezing was repeated after thawing. Liposomes became larger when frozen in the liquid nitrogen followed by thawing, and the extent of the exotherm due to freezing of the intraliposomal solution increased as a result. In the presence of Pseudomonas syringae, freezing temperature of the extraliposomal solution shifted to a higher subzero temperature and amount of freeze-dehydration from the liposome increased, which caused the decrease in the exothermic heat due to the intraliposomal freezing. Judging from the leakage of encapsulated ATP, it was indicated that the vesicular structure of lecithin liposomes was hardly destroyed by the intraliposomal freezing, nor was it destroyed by the substantial freeze-dehydration.
