Industrial Crops and Products 32 (2010) 297–304 Contents lists available at ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop Twin-screw extruder for oil processing of sunflower seeds: Thermo-mechanical pressing and solvent extraction in a single step I. Amalia Kartika a,∗ , P.Y. Pontalier b , L. Rigal b a Department of Agroindustrial Technology, FATETA-IPB, Darmaga Campus, P.O. Box 220, Bogor 16002, Indonesia b Laboratoire de Chimie Agro-Industrielle, UMR 1010 INRA/INPT-ENSIACET, 4, allée Emile Monso, BP 44362, Toulouse 31432, France article info Article history: Received 29 December 2009 Received in revised form 11 May 2010 Accepted 12 May 2010 Keywords: Twin-screw extruder Sunflower oil Mechanical pressing Solvent extraction abstract A new application of twin-screw extruder as a machine to conduct a thermo-mechanical pressing and a solvent extraction of sunflower oil in a single step and in a continuous mode was studied. Experiments were conducted using a CLEXTRAL BC 45 co-rotating twin-screw extruder and whole sunflower seeds with fatty acid methyl esters as a solvent. The influences of screw rotation speed (S S ), feed rate (Q S ) and solvent-to-solid (S/S) ratio were examined to define the best performance of the oil extraction yield, the oil quality and the specific mechanical energy. Generally, the screw rotation speed, feed rate and solvent-to-solid ratio affected oil extraction yield. An increase of oil extraction yield was observed as screw rotation speed and feed rate were decreased, and solvent-to-solid ratio was increased. In addition, oil extraction yield increased as screw rotation speed and feed rate were simultaneously increased to Q S /S S ratio of 0.2. Highest oil extraction yield (98%) with best cake meal quality (residual oil content lower than 3%) was obtained under screw rotation speed of 185 rpm, feed rate of 30 kg/h, and solvent-to-solid ratio of 0.55. Furthermore, the operating parameters and solvent-to-solid ratio influenced energy input. A decrease of screw rotation speed and feed rate followed by an increase of solvent-to-solid ratio increased energy input, particularly specific mechanical energy input. © 2010 Elsevier B.V. All rights reserved. 1. Introduction In the food industry, twin-screw extruders play an important role in transforming the material physically and chemically in a single step. The main application of the twin-screw extruder is most usually found in the production of various products such as snacks, cereals and pet food. In several studies the twin-screw extruder is considered also as a reactor to conduct a thermo-mechano- chemical action and a liquid/solid extraction, as in hemicelluloses extraction (N’Diaye et al., 1996; N’Diaye and Rigal, 2000) and fatty acid esters production (Lacaze-Dufaure et al., 1996). Actually, the application of twin-screw extruder has been successfully car- ried out to extract oil from oleaginous seeds (Isobe et al., 1992; Guyomard, 1994; Bouvier and Guyomard, 1997; Lacaze-Dufaure et al., 1999a; Amalia Kartika et al., 2005, 2006), and to conduct an alcohol and fatty acid methyl esters extraction of sunflower oil (Lacaze-Dufaure et al., 1999b; Amalia Kartika et al., 2003). Conventional industrial oil extraction from oilseeds is com- monly realized through mechanical pressing with a hydraulic or single expeller press, followed by solvent extraction. The combi- ∗ Corresponding author. Tel.: +62 251 862 19 74; fax: +62 251 862 19 74. E-mail address: ikatk@yahoo.com (I. Amalia Kartika). nation of these operations produced oil extraction yield up to 98% with residual oil content in cake meal of 0.5–1.5% (Campbell, 1983). The solvent extraction most commonly used today is percolation extraction with a countercurrent flow using hexane as a solvent (Johnson and Lusas, 1983; Wan et al., 1995; Conkerton et al., 1995; Proctor and Bowen, 1996; Hu et al., 1996). However, flammability, toxicological risks, health and environmental concerns have moti- vated interest to replace hexane. Several alternative solvents have been reported by a few researchers (Hron et al., 1982, 1992, 1994; Hron and Koltun, 1984; Johnson et al., 1986; Lusas et al., 1990; Abraham et al., 1993; Abu-Arabi et al., 2000; Devittori et al., 2000; Hanmounjai et al., 2000; Hojilla-Evangelista and Johnson, 2002; Kwiatkowski and Cheryan, 2002; Kiriamiti et al., 2002; Gomez and Martinez de la Ossa, 2002). The application of solvent derived from vegetable oils, such as fatty acid methyl esters, has attracted attention recently from a few researchers due to its environmental benefits, and because vegetable oils are non-toxic, renewable and biodegradable (Gérin, 2002). The great capability of the twin-screw extruder to conduct diverse functions and processes comes from its characteristics. According to Dziezak (1989), those advantages include (i) ability to provide better process control and versatility, especially in pump- ing efficiency, controlling residence time distribution and unifor- mity of processing, (ii) ability to process specialty formulation 0926-6690/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2010.05.005