Gr. List et al., SUPERCRITICAL CO2 DEGUMMING AND PHYSICAL REFINING OF SOYBEAN OIL, Journal of the American Oil Chemists' Society, 70(5), 1993, pp. 473-476
A hexane-extracted crude soybean oil was degummed in a reactor by coun
ter-currently contacting the oil with supercritical CO2 at 55 MPa at 7
0-degrees-C. The phosphorus content of the crude oil was reduced from
620 ppm to less than 5 ppm. Degummed feedstocks were fed (without furt
her processing, i.e., bleaching) directly to a batch physical refining
step consisting of simultaneous deacidification/deodorization (1 h @
260-degrees-C and 1-3 mm Hg) with and without 100 ppm citric acid. Fla
vor and oxidative stability of the oils was evaluated on freshly deodo
rized oils both after accelerated storage at 60-degrees-C and after ex
posure to fluorescent light at 7500 lux. Supercritical CO2-processed o
ils were compared with a commercially refined/bleached soybean oil tha
t was deodorized under the same conditions. Flavor evaluations made on
noncitrated oils showed that uncomplexed iron lowered initial flavor
scores of both the unaged commercial control and the CO2-Processed oil
s. Oils treated with .01% (100 ppm) citric acid had an initial flavor
score about 1 unit higher and were more stable in accelerated storage
tests, than their uncitrated counterparts. Supercritical CO2-processed
oil had equivalent flavor scores, both initially and after 60-degrees
-C aging and light exposure as compared to the control soybean oil. Re
sults showed that bleaching with absorbent clays may be eliminated by
the supercritical CO2 counter-current processing step because consider
able heat bleaching was observed during deacidification/deodorization.
Colors of salad oils produced under above conditions typically ran 3Y
0.7R.