A laboratory assembled SC-CO2 extraction apparatus (Fig. 1)
consisted of an extractor vessel (HIP Inc. Erie, PA), compression
pump (Haskel Co. Barbank, CA), pressure regulator (HIP Inc. Erie,
PA), and pressure gauge (MacDaniel Controls Co.). Twenty-five
grams of pumpkin seed powder was placed in the stainless steel
extractor with filters at the top and bottom to retain the small particles.
The liquid carbon dioxide was cooled through a glycol chiller,
compressed (using the liquid pump) and allowed to enter the
extractor at the bottom through a hot water bath (for temperature
control). The flow rate of CO2 was kept constant at 0.25 L/min forall treatments by manually adjusting the gas flow valve and monitoring
the rate through a gas flowmeter. The extractor was
brought up to the desired supercritical pressure and temperature.
SC-CO2 was then pushed upward through the sample powder. Oil
enriched SC-CO2 was then discharged into the separator where carbon
dioxide was depressurized. The gaseous carbon dioxide moved
out through the gas meter leaving the extracted oil in the separator.
The pressures in both the extractor and separator were controlled
manually using a back-pressure regulator. After
extraction, the oil was collected at the bottom of the separator into
300 mL hexane placed there prior to the extraction process, and
then stored in a refrigerator for analysis. Hexane was removed
from the extracted oil and concentrated using a rotary vacuum
evaporator at 45 C. During this process, a gentle stream of nitrogen
was passed though the oil for complete removal of hexane
and to remove oxygen. The yield of the oil was then measured
gravimetrically. In order to optimize the extraction process, extraction
was carried out at different conditions using a CCRD design
and an RSM model.