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Super critical Fluid Extraction Applications 449

Carbon Dioxide: Temperature-Pressure Diagram
10000.0
Melting line

1000.0

Solid Liquid Critical
Pressure, bar 10.0 Saturation line point
100.0

Sublimation line Triple point

1.0 Vapor
Copyright 1999 Chemical logic corporation
Drawn with CO Tab V1.0
2
0.1
–100 –90 –80 –70 –60 –50 –40 –30 –20 –10 0 10 20 30 40 50
Temperature, °C
FIGURE 16.1 PT diagram of carbon dioxide. The supercritical region exists at all
pressures and temperatures above the critical point. (source: http://www.
chemicalogic.com/download/co2_phase_diagram.pdf)

properties of carbon dioxide are shown in the pressure-temperature
phase diagram (Fig. 16.1).
Supercritical CO extraction of vegetable oil has been studied
2
from a processing point of view, and a wide range of seed species has
been explored, including cottonseed, soybean, peanut, and rapeseed
(Reverchon et al. 2000). Fattori et al. (1988) evaluated the feasibility
and merits of supercritical CO extraction as an alternative to hexane
2
extraction in the canola oilseed industry. The experiment was con-
ducted at temperatures ranging from 25 to 90°C and pressures rang-
ing from 10 to 36 MPa. The oil solubility in CO was found to be
2
strongly dependent on pressure and weakly dependent on temperature.
The highest observed oil solubility was 11 mg/g CO and occurred
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at 36 MPa and 55°C. The amount of oil extractable from flaked and
cooked seeds was comparable to that obtained by conventional hex-
ane extraction. Przybylski et al. (1998) analyzed the composition and
oxidative stability of oil fractions collected during the process of
supercritical CO extraction at 40°C and 41.4 MPa. The results showed
2
that linolenic acid composition decreased, and the amounts of phos-
pholipid increased as the CO volume increased. The fraction obtained
2
at the end of extraction contained higher amounts of unsaponifiables
and phospholipids and showed better oxidative stability.
Supercritical CO extraction of lipids from lipid-bearing fungal or
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algal biomass has also been studied (Walker et al. 1999; Badal and