Characterization and supercritical carbon dioxide extraction of walnut oil
Walnut (Juglans regia L.) oil was extracted with compressed carbon dioxide (CO2) in the temperature range of 308 to 321 K and in the pressure range of 18 to 23.4 MPa. The influence of particle size was also studied at a superficial velocity of 0.068 cm/s, within a tubular extractor of 0.2 L capacity (cross-sectional area of 16.4 cm2). FFA, sterol, TAG, and tocopherol compositions were not different from those of oil obtained with n-hexane. The main FA was linoleic acid (56.5%), followed by oleic acid (21.2%) and linolenic acid (13.2%). The main TAG was LLL (linoleic, linoleic, linoleic) (24.4%), followed by OLL (oleic, linoleic, linoleic) (19.6%) and LLLn (linoleic, linoleic, linolenic) (18.4%). The main component of sterols was β-sitosterol (85.16%), followed by campesterol (5.06%). The amount of cholesterol was low (0.31 and 0.16% for oils extracted by n-hexane and supercritical fluid extraction, respectively. The CO2-extracted oil presented a larger amount of tocopherols (405.7 μg/g oil) when compared with 303.2 μg/g oil obtained with n-hexane. Oxidative stability determined by PV and the Rancimat method revealed that walnut oil was readily oxidized. Oil extracted by supercritical CO2 was clearer than that extracted by n-hexane, showing some refining. A central composite, nonfactorial design was used to optimize the extraction conditions using the software Statistica, Version 5. The best results were found at 22 MPa, 308 K, and particle diameter (Dp) −0.1 mm.
Key WordsJuglans regia L. lipids oil characterization supercritical CO2 walnut
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- 1.Rattray, J.B., Spring: A New Beginning, inform 11:303–311 (2000).Google Scholar
- 3.Greve, C., G. McGranahan, J. Hansey, R. Snyder, K. Kelly, D. Goldhamerer, and J. Labavitch, Variation in Polyunsaturated Fatty Acid Composition of Persian Walnut. J. Soc. Hort. Sci. 117:518–522 (1992).Google Scholar
- 4.Savage, G.P., P.C. Dutta, and D.L. McNeil, Fatty Acid and Tocopherol Contents and Oxidative Stability of Walnut Oils, J. Am. Oil Chem. Soc. 76:1059–1063 (1999).Google Scholar
- 8.Abbey, M., M. Noakes, G.B. Belling, and P.J. Nestel Partial Replacement of Saturated Fatty Acids with Almonds or Walnuts Lowers Total Plasma Cholesterol and Low-Density-Lipoprotein Cholesterol, Am. J. Clin. Nutr. 59:995–999 (1994).Google Scholar
- 11.Zambon, D., J. Sabaté, S. Munoz, B. Campero, E. Casals, M. Merlos, J.C. Laguna, and E. Ros, Substituting Walnuts for Monounsaturated Fat Improves the Serum Lipid Profile of Hypercholesterolemic Men and Women. A Randomized Crossover Trial, Ann. Intern. Med. 132:538–546 (2000).Google Scholar
- 12.Dakovic, S., J. Turkulov, and E. Dimic, The Quality of Vegetable Oils Got by Extraction with CO2, Fat Sci. Technol. 91: 116–119 (1989).Google Scholar
- 13.Fors, S.M., and C.E. Eriksson, Characterization of Oils Extracted from Oats by Supercritical Carbon Dioxide, Lebensm. Wiss. Technol. 23:390–395 (1990).Google Scholar
- 15.Gómez, M.A., C.P. López, and E. Martínez de la Ossa, Recovery of Grape Seed Oil by Liquid and Supercritical Carbon Dioxide: A Comparison with Conventional Solvent Extraction, Chem. Eng. J. 61:227–231 (1996).Google Scholar
- 16.Kuk, M.S., and M.K. Dowd, Supercritical CO2 Extraction of Rice Bran, J. Am. Oil Chem. Soc. 75:623–628 (1998).Google Scholar
- 17.Devittori, C., D. Gumy, A. Kusy, L. Colarow, C. Bertoli, and P. Lambelet, Supercritical Fluid Extraction of Oil from Millet Bran, J. Am. Oil Chem. Soc. 77:573–579 (2000).Google Scholar
- 18.Gómez, M.A., and E. Martínez de la Ossa, Quality of Wheat Germ Oil Extracted by Liquid and Supercritical Carbon Dioxide, J. Am. Oil Chem. Soc. 77:969–974 (2000).Google Scholar
- 20.Official Journal of the European Communities L248:15–22 (1991).Google Scholar