Thermal conductivity of lipidic emulsions and its use for production and quality control

Thermal conductivity of lipidic emulsions has been experimentally determined by the probe method. To this purpose a special probe has been designed and built in laboratory, with small diameter (0.6 mm) and a high length to diameter ratio (100). The temperature sensor of the probe (type T thermocouple) and the heater (Pt wire) were properly calibrated. Moreover, the probe performance has been tested by means of a pure liquid (glycerin) having well known thermal conductivity by literature. Differences of about 1.5% at ambient temperature in thermal conductivity values between literature and experiments were found. On lipidic emulsions first thermal conductivity has been measured in the temperature range 1040°C, second the same property as a function of time at constant temperature (40°C), then the values after freezing at –15°C and reheating at 20 °C; and last the kinetics of degeneration. Results show a significant difference between thermal conductivity values of a new emulsion (0.51 W/m K), compared with the creamed one (0.62 W/m K), and the decayed one (0.68 W/m K ). It has also put into evidence why the frozen emulsion cannot be used for intravenous injection, i.e. viscosity increases because of breaking of the oil particles. Finally information about the kinetics of the degeneration process have been obtained. The uncertainty resulting from the calibration and tests justifies the possible use of the measurement technique for process control of production, and also for quality control in the clinical practice.