Abstract—The effects of enzyme action and heat pretreatment on oil extraction yield from sunflower kernels were analysed using hexane extraction with Soxhlet, and aqueous extraction with incubator shaker. Ground kernels of raw and heat treated kernels, each with and without Viscozyme treatment were used. Microscopic images of the kernels were taken to analyse the visible effects of each treatment on the cotyledon cell structure of the kernels. Heat pretreated kernels before both extraction processes produced enhanced oil extraction yields than the control, with steam explosion the most efficient. In hexane extraction, applying a combination of steam explosion and Viscozyme treatments to the kernels before the extraction gave the maximum oil extractable in 1 hour; while for aqueous extraction, raw kernels treated with Viscozyme gave the highest oil extraction yield. Remarkable cotyledon cell disruption was evident in kernels treated with Viscozyme; whereas steam explosion and conventional heat treated kernels had similar effects. . Keywords—Enzyme-assisted aqueous and hexane extraction, heat pretreatment, sunflower cotyledon structure, sunflower oil extraction I. INTRODUCTION NDUSTRIAL processes for the recovery of the easily extractable oil from sunflower seeds is usually achieved by conventional mechanical pressing with expeller press, or through mechanical press followed by extraction with an organic solvent such as commercial grade hexane or ether [1], [2]. The following processing steps are usually employed, such as grinding and treatment by moisture with the reason of weakening the oil-bearing cell coats and preparing the seed for optimal oil extraction [3], [4]. However, although some of the oil content in sunflower seeds is easily extractable by simple use of conventional mechanical press or organic solvent, the rest of oil matter is strongly bonded to the seed matrix and extensive treatments are required in order to separate this fraction. From reports it is possible to achieve oil yields in excess of 95% using conventional solvent-based processes [5], [6]. However, solvent extraction has disadvantages such as expensive operational costs and capital investment; poor quality of end-products due to the high processing temperatures; safety and environmental implications including plant safety problems, emissions of volatile organic E. Danso-Boateng is with the Department of Chemical Engineering, Kumasi Polytechnic, P. O. Box 854, Kumasi, Ghana (phone: 233-268- 595513; fax: 233-322-022387; e-mail: edansoboateng@yahoo.com). compounds into the atmosphere and risks of fire and explosion in large installations [7], [8]. In 2001, the U.S. Environmental Protection Agency issued stringent guidelines for hexane emissions by vegetable oil extraction facilities [9]. As a result, the edible oil industry is looking for suitable and environmentally friendly methods of edible oil extraction [10]. Mechanical pressing processes are environmentally friendly and produce oil of high quality [11] as compared to solvent extraction. Some drawbacks of mechanical pressing include higher power consumption, high working costs, and lower oil recovery (yield) [12]. This has renewed interest in alternative oil extraction processes that may have less environmental effects as well as produce high and quality oil yield and also improve the potential application of the residual meal. Aqueous extraction processes are reported to represent a novelty in extraction technology for processing oilseeds. It represents no risks of fire and explosion, the solvent (water) is not toxic, ensures high quality products - oil and proteins [13], [14]. The main disadvantages compared to the conventional methods, are the lower efficiency of oil extraction yield, and the less stability of the product containing more residual oil [13]. Various studies suggest that enzymes can be used to enhance oil yield in oilseed extraction processes, by debilitating the oil-bearing seed cotyledon cell-wall, facilitating oil release prior to or during the oil extraction process. Enzyme pre-treatment before mechanical pressing for enhanced oil extractability has been reported for virgin-grade olive oil [15]), Guevina avellana mol [16], and rapeseed oil and sunflower oil [17], and cottonseed [18] using various enzyme mixtures containing pectinase, cellulase, and hemicellulase. Improved oil yield by some authors have been reported for enzyme-assisted solvent extraction processes. Enzyme pretreatment followed by solvent extraction has been reported for soybean oil [19], Ricinodendron heudelotii seeds oil [20], and sunflower seeds [21]. However, these studies did not investigate the possibility of achieving high oil recovery yield at shorter extraction time when the oilseeds are enzymatically and/or heat treated. Studies on enzymatic aqueous extraction have been reported. Moreau et al. [22] applied different commercial cellulases in aqueous medium to to significantly increased oil extractability of corn oil, obtaining yields of about 80%. The use of enzymes for enhance oil recovery in aqueous vegetable oil extraction processes have also been reported for peanut E. Danso-Boateng Effect of Enzyme and Heat Pretreatment on Sunflower Oil Recovery Using Aqueous and Hexane Extractions I International Journal of Chemical and Biological Engineering 4:1 2011 28