DEVELOPMENT AND UTILIZATION OF NEW OILSEED CROPS AND PRODUCTS
Location: Bio-oils Research Unit
Title: Quality of field pennycress oil obtained by screw pressing and solvent extraction
Submitted to: Association for the Advancement of Industrial Crops Conference
Publication Type: Abstract Only
Publication Acceptance Date: September 11, 2011
Publication Date: September 11, 2011
Citation: Evangelista, R.L., Isbell, T., Dunn, R.O., Cermak, S.C. 2011. Quality of field pennycress oil obtained by screw pressing and solvent extraction [abstract]. Association for the Advancement of Industrial Crops Conference. p. 9.
Field pennycress (Thlasphi arvense L., Brassicaceae) is a winter annual that grows widely in temperate North America. Its seeds contain up to 36% oil (dry basis, db) with the major fatty acid being erucic acid (38 %). With an estimated seed production of 1,700 – 2,200 kg/ha, pennycress can be a major source of oil for biofuel. The early harvest date of pennycress compared to other winter annual oilseed crops makes it suitable for a two-crop rotation with soybeans in most of the Midwestern United States. This allows for the production of oil for industrial application without displacing commodity crops for food use.
The 2009 harvest of about 1,500 kg of pennycress seeds from a native stand near Peoria, Illinois provided our first opportunity to conduct oil extraction studies. The goal was to evaluate the quality of the oil obtained by full pressing and pre-pressing followed by solvent extraction. The starting seed had 9.5 % moisture content (MC) and 31.4% oil (db). Cooked and uncooked seeds (60 kg) were screw pressed using a heavy duty French Laboratory Screw Press (Model L250). Seed cooking was done using a steam-heated three-deck French Seed Cooker/Conditioner (Model 324). The seeds were heated to 82oC and held at this temperature for 20 min. The press cakes (350 g/batch) from cooked and cold-pressed seeds were extracted with hexane using a soxhlet apparatus. Oil was recovered from the miscella using a rotary evaporator. The press cakes and hexane defatted meals were analyzed for oil and moisture content. The oils were analyzed for free fatty acid (FFA), phosphatides (measured as phosphorus [P]), and sulfur (S) contents.
Cold pressing pennycress seeds with 9.5% MC produced press cake with 10.7% oil (db), extracting 74% of the oil. Cooking reduced the seed MC to 5.3% and improved the extraction yield by 19%. Hexane-defatted press cakes had residual oil content of = 0.03%, increasing the overall oil yield to 99.9%. Oil from cold-pressed seeds had the lowest FFA, P, and S contents at 0.23%, 1 ppm, and 20 ppm, respectively. Cooking the seeds before pressing increased the oil’s FFA to 0.39%, P to 67 ppm, and S to 373 ppm. Hexane co-extracted significantly more P and S compounds with the oil from the press cakes. Compared to hexane-extracted oil from cold-pressed cake, the oil from cooked seed press cake had higher P (740 vs. 506 ppm) and similar S (172 vs. 162 ppm). Phosphatides and sulfur compounds are known to poison catalysts. Therefore, the degree of oil refining needed to bring the oil to the specification of an intended application depends on the method of oil extraction. Phosphatides are easily removed by degumming while sulfur compounds are only partially removed in degumming, caustic refining, bleaching, and deodorization.