MICROEMULSIONS BASED OIL SOYBEAN PHOSPHATIDYLCHOLINE AND TRIGLYCERIDES - PHASE-BEHAVIOR AND MICROSTRUCTURE

We have studied the phase behavior and microstructure of water/1-propa nol/soybean phosphatidylcholine (SbPC)/triglyceride systems. Microemul sions are formed with both medium-chain triglycerides (MCT) and long-c hain triglycerides. The amount of SbPC and I-propanol needed to form a microemulsion increases as the chain length of the triglyceride incre ases. The MCT system was investigated in more detail and compared with a hexadecane system. The phase behavior and pulsed field gradient NMR data for the MCT system suggest that the microemulsions formed at low SbPC concentrations and 0 < alpha < 0.5, where alpha is defined as th e weight fraction of oil/(oil + water), are of a bicontinuous type. Th e self-diffusion data for the microemulsions formed at higher SbPC con centrations clearly indicate that there is some structure also in thes e microemulsions with an oil-in-water droplet structure at the water r ich side and a gradual change to a bicontinuous structure when the MCT concentration is increased. The bicontinuity appears to be preserved even at low water concentrations. The microstructure of the microemuls ion in this part of the phase diagram is, however, less well-defined, most probably with large polydispersity and rapid fusion and fission o f the oil and water domains. The hydrodynamic radius and aggregation n umber of the SbPC aggregates formed in a mixture of 22.5 wt % SbPC, 22 .5 wt % I-propanol, and 55 wt % water was calculated as 27.5 Angstrom and 68 SbPC molecules/aggregate, respectively.