ABSTRACT
Supercritical fluid (SF) processing as an alternative to
conventional extraction, fractionation, reaction, and par-
ticle formation processes offers several advantages to
food processors. A single SF, which has properties that
span between those of a gas and a liquid, can simulate the
solvent power or density of a range of organic solvents
through adjustments in temperature and pressure for
selective dissolution of various compounds. The high
diffusivity and low viscosity of SF enhance mass transfer
in extraction processes. Supercritical carbon dioxide
(SCO2) is the most commonly used SF. It is an environ-
mentally benign and non-toxic solvent. It is easily
handled and readily available; it can be recycled and
reused; it is non-flammable; it does not leave solvent
residue that can contaminate the food substrate or extract;
and it is inexpensive. The low critical temperature of
SCO2 is an advantage in processing, not only for energy
savings, but because heat-induced damage to the substrate
is minimized. SCO2 also inhibits mold and bacterial
growth on foods and has potential for use as a sterilant
in the medical and food industries.[1]
SUPERCRITICAL EXTRACTION
Supercritical fluid extraction (SFE) research is active at
several facilities throughout the United States and the
world. Because SCO2 is an ideal solvent for selectively
solubilizing lipophilic substances without causing thermal
degradation of the product, early research was conducted to
examine its potential as a replacement for hexane and other
organic solvents in extracting seed oils. Later research on
SFE was conducted in laboratory studies and in some cases
pilot-scale studies, for extraction, fractionation, refining,
and deodorization of lipids or essential oils; flavor and
aroma isolation; and bioactive compounds and antioxidants
isolation. SCO2 has been used to extract soybean, rice bran,
sunflower, rapeseed, wheat germ, and corn germ oils; soy-
bean oil and olive oil deodorizer distillates; evening prim-
rose oil, marine oils, lemon oil, bergamot oil, paprika
oleoresin, beta carotene, lycopene, tocopherols, black pep-
per, red pepper, ginger, turmeric, nutmeg, vanilla; phenols
and tannins from grape seeds; herbicides from eggs, algae,
and microalgae; coffee aromas; cholesterol from milk fat
and eggs; oil from potato chips; and various pesticides
from foods. This list is not exhaustive and details on
these and other applications are found in Reverchon[2]
and Herrero et al.[3] and Kim and Mendis[4] and Sahena
et al.[5] and Pourmortazavi and Hajimirsadeghi[6] and Shi
et al.[7] and Martinez[8] and Temelli.[9]
Supercritical ethane and propane used alone or in mix-
tures with SCO2 are also suitable SFE solvents for food use
and preferable to SCO2 in some cases because of their
improved extraction capabilities. They have been used
for cholesterol removal from meat, eggs, and dairy
foods[10] and, for example, the extraction of orange peel
oils.[11] However, their use has been limited because of
greater solvent costs and flammability concerns.
