J Sci Food Agric 1994,64,257-263 Analysis of Volatile Compounds from Supercritical Extracted Soybeans by Headspace Gas Chromatography and Thermal Desorption of a Polymer Adsorbent Janet M Snyder* and Jerry W King Food Quality & Safety Research Unit, National Center for Agricultural Utilization Research,Agricultural ResearchService, US Department of Agriculture, 1815N. University Street, Peoria, Illinois, 61604, USA (Received 11 January 1993; revised version received 14 June 1993; accepted 19 October 1993) Abstract: Soybean flakes were extracted with supercritical carbon dioxide to produce a solvent-free, good-quality soybean oil. Volatile compounds from the supercritical fluid extracted (SFE) oil and from a hexane-extractedcrude soybean oil were analyzed by dynamic headspace gas chromatographic methods to deter- mine qualitative differences between the extraction methods. The major differ- ence in the volatile profiles was the higher concentration of hexane in the solvent-extracted oil. During the SFE process,volatile compounds were trapped on a porous polymer trap attached at the exhaust port of the SFE apparatus. The volatile profile obtained from the sorbent trap was found to be similar to the headspace profile from the SFE/soybean oil removed during the same extraction. In addition, crude soybean oil was heated in a stirred reactor and the volatiles, which were stripped by supercritical carbon dioxide in an attempt to improve oil properties, were collected on sorbent traps and analyzed by the above method for comparison. The described methodology permits the characterization of vola- tiles and semivolatiles in SFE soybean oil and can be used to monitor the extrac- tion and quality of the resultant oil. Key words: hexane-extracted, supercritical extracted, GC/MS, soybean oil, Tenax. INTRODUCTION Volatile components from a variety of samples, such as milk products, vegetable oils and floral specimens, Soybeans extracted with supercritidal carbon dioxide (SC-CO,) yield an oil which is comparable to hexane- extracted degummed oil devoid of any solvent residue (Stahl et al 1980; Friedrich et al 1982; List and Fried- rich 1985; List and King 1989). In addition, the super- critical fluid extraction (SFE) process has been shown to yield both an oil and meal that are improved in color and equivalent in flavor to those obtained from conven- tional extraction and refining processes (Friedrich and List 1982; Friedrich and Pryde 1984; Christianson et al 1984; List et al 1984; Eldridge et al 1986). Smelling of the decompressed CO2 stream as it exits the extractor suggests the presence of many odoriferous components which are being removed during the extraction process. have been trapped on porous polymer adsorbents to collect and concentrate the volatile analytes (Mills 1986; Selke and Frankel 1987; Raghavan et al 1989). In addi- tion, on-line collection of pesticides ontd a sorbent trap has been accomplished using SFE (Patt et al 1992). The aim of this work was to use SFE to analyze lipid oxidation volatiles, to compare the volatiles in SFE- derived and hexane-extracted soybean oils and to examine a new experimental thermal processing pro- cedure. EXPERIMENTAL Soybeans were cracked, dehulled and flaked; 60 g of the flakes were extracted with SC-CO, using a laboratory- * To whom correspondence should be addressed. built extractor (King et al 1989). The apparatus was 257