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Lipid Extraction from Wheat Flour Using Supercritical Fluid Extraction¹

¹Cooperative investigations, U.S. Department of Agriculture (USDA), Agricultural Research Service (ARS), and the Department of Grain Science and Industry, Kansas State University. Contribution No. 03-30-J from the Kansas Agricultural Experiment Station, Manhattan, KS 66506. Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product to the exclusion of others that may also be suitable. ²USDA, ARS, Grain Marketing and Production Research Center, Manhattan, KS 66502. ³Department of Grain Science and Industry, Kansas State University, Manhattan, KS 66506. ⁴Current address: Atrix Labs, 2579 Midpoint Drive, Fort Collins, CO 90525-4417. ⁵Corresponding author. Phone: 785-776-2703; Fax: 785-537-5534; E-mail: okchung@gmprc.ksu.edu

Environmental concerns, the disposal cost of hazardous waste, and the time required for extraction in current methods encouraged us to develop an alternate method for analysis of wheat flour lipids. Supercritical fluid extraction (SFE) with carbon dioxide has provided that medium and the method is fully automatic. Crude fats or nonstarch free lipids (FL) were extracted from 4–5 g of wheat flour by an SFE system. To develop optimum conditions for SFE, various extraction pressures, temperatures, and modifier volumes were tried to provide a method that would produce an amount of lipids comparable to those extracted by the AACC Approved Soxhlet Method and the AOCS Official Butt Method using petroleum ether as solvent. Using several wheat flour samples, the best conditions were 12.0 vol% ethanol (10.8 mol%) at 7,500 psi and 80°C to extract the amount of FL similar to those by the AACC and AOCS methods. Using solid-phase extraction, lipids were separated into nonpolar lipid (NL), glycolipid (GL), and phospholipid (PL) fractions. The mean value of five flours was 1.15% (flour weight, db) by the SFE method, 1.07% by the Butt method, and 1.01% by the Soxhlet methhod. The SFE-extracted lipids contained less NL and more GL than either the Butt or Soxhlet methods. All three methods extracted lipids with qualitatively similar components. The overall benefit for SFE over the Soxhlet or Butt methods was to increase the number of samples analyzed in a given time, reduce the cost of analysis, and reduce exposure to toxic chemicals.