Journal of the Science of Food and Agriculture J Sci Food Agric 85:2167–2174 (2005) DOI: 10.1002/jsfa.2244 Supercritical carbon dioxide extraction of oil and α -tocopherol from almond seeds Lucia Leo, 1 Leonardo Rescio, 2 Loredana Ciurlia 2 and Giuseppe Zacheo 1∗ 1 CNR, Istituto di Scienze delle Produzioni Alimentari, Via Lecce-Monteroni, 73100 Lecce, Italy 2 PIERRE CHIMICA srl, SS 476 Km 17, 650 Zona Industriale, 730213 Galatina (LE), Italy Abstract: The objective of this study was to extract oil and tocopherols from almond seeds using supercritical carbon dioxide and to compare this extraction with a traditional solvent method. Oil and tocopherol extraction rates were determined as functions of the pressure (350–550 bar), temperature (35–50 ◦ C) and CO 2 flow rate (10–30 kg h −1 ), using a 10-l vessel. The effects of matrix particle size on extraction yield were also studied and it was demonstrated that extraction yield is greatly influenced by particle size. Maximum recovery was obtained in the first 2–3 h of extraction at a pressure of 420 bar, a temperature of 50 ◦ C and a flow rate of 30 kg h −1 CO 2 . These results suggest that the elevated initial oil and tochopherol solubility is related to the increased proportion of fatty acids in the initial extract. The results were compared with those obtained when hexane/methanol was used as a solvent.  2005 Society of Chemical Industry Keywords: carbon dioxide; extraction; oil; solubility; tocopherol INTRODUCTION Carbon dioxide (CO 2 ) is often used in the develop- ment of supercritical fluid extraction (SFE) instead of the organic solvents normally employed in conven- tional extraction methodologies. The main advantages of using carbon dioxide fluid are: a reduced potential for the oxidation of extracted solutes, higher selectivity, increased sample throughput, shorter extraction time and a low critical temperature. The latter is beneficial in extracting thermally labile compounds, such as nat- ural vegetable products. Supercritical carbon dioxide also has chemical inertness, suitable solvent strength, permits the separation of compounds of widely differ- ent polarities and molecular masses, has low cost and, what is more, can be removed from the extracted prod- ucts without leaving any chemical residue. In addition, carbon dioxide is both non-toxic and non-explosive and its use can reduce the consumption of organic solvents; this is especially useful for the production of natural products used in foods and pharmaceuticals. There are several excellent articles on the use of supercritical carbon dioxide methodologies in various analytical areas, including the extraction of vegetable oil and of fat-soluble vitamins. 1–4 Knowledge of the solubility of vegetable oil and its fat-associated products in supercritical CO 2 along with pressure and temperature are important for the successful application of this technology. The extraction conditions for specific solutes or classes of solutes from the vegetable matrix can also be optimised by changing the flow rate of the supercritical fluid or its pressure or temperature. Recently, an increasing interest in both the detection and the search for new oil and vitamin extraction techniques has been reported, and supercritical CO 2 extraction methods have been successfully applied in the extraction of oils from orange peel, 5 hazelnut, 6 olive, 7 blackcurrant and vineyard grape. 8 Despite the large number of matrices processed, 9 only some models of supercritical CO 2 have been published. Nevertheless, to optimize the extraction conditions, a relationship between the composition of vegetable oils and their solubility in supercritical CO 2 must be taken in account. 8 Almond is one of the major nut tree crops of the Mediterranean region. Almond kernel, analysed by using a conventional solvent method for the isolation of oil and fat-soluble vitamins, is shown to consist mainly of (g kg −1 ): lipids (450–600), proteins (200), and carbohydrates (200), with other elements, such as tocopherols, present in much smaller quantities (tocopherols 0.4–0.8). 10 – 12 The major lipid species were found to be (g kg −1 total fatty acids): oleic acid, linoleic acid (100–170), and palmitic acid (55–70). The objective of our study was to develop a supercritical CO 2 extraction method for almond seed oil and subsequently to characterise the oil and tocopherols present in seed extracts. The supercritical CO 2 method for extraction of the lipid components and tocopherols used a 10-l pilot plant. The effect of pressure, temperature, solvent flow and particle size on the extraction rate were analysed. The results of ∗ Correspondence to: Giuseppe Zacheo, CNR, Istituto di Scienze delle Produzioni Alimentari, Via Lecce-Monteroni, 73100 Lecce, Italy E-mail: giuseppe.zacheo@ispa.cnr.it (Received 1 September 2004; revised version received 27 January 2005; accepted 16 March 2005) Published online 20 June 2005  2005 Society of Chemical Industry. J Sci Food Agric 0022–5142/2005/$30.00 2167