SUPERCRITICAL CO2 DEGUMMING AND PHYSICAL REFINING OF SOYBEAN OIL

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.