ABSTRACT
Submicron-sized oil-in-water emulsions have been clinically used for decades in parenteral nutrition and also as colloidal drug carrier systems for poorly water soluble substances. Colloidal lipid suspensions can principally be prepared by the same manufacturing techniques as lipid emulsions, such as high pressure homogenization. Lipid emulsions used in parenteral nutrition and drug delivery are composed of vegetable oils which are emulsified in an aqueous phase using fractionated egg or soya lecithins as emulsifying agents. Electron microscopic pictures of freeze fractured replica of tripalmitate dispersions display platelet-like particles independent of the emulsifier composition. The physicochemical processes of melt-emulsified tripalmitate dispersions during the cooling step can be directly monitored by polarized light microscopy of crude lecithin/sodium glycocholate stabilized tripalmitate dispersions. Whereas phospholipid stabilized soy bean oil-in-water emulsions generally display a reasonable long-term stability, the corresponding melt-homogenized tripalmitate suspensions tend to form semisolid gels upon cooling of the hot tripalmitate-in-water emulsions.
