Supercritical fluid extraction of Cucurbita ficifolia seed oil

Pumpkin, Cucurbita ficifolia, seed oil was extracted with supercritical carbon dioxide (SC-CO2) in the temperature range of 308 - 318 K and in the pressure range of 18 - 20 MPa. In addition, the influence of the superficial velocity within a tubular extractor was studied. The oil content determined by a Soxhlet apparatus was 43.5%. Physical and chemical characteristics of the oil were obtained. The results in terms of free fatty acids contents were compared with those obtained when n-hexane was used as the solvent, and no significant differences between the oils extracted by both methods were found. The main fatty acid was omega6-linoleic acid ( about 60%), followed by palmitic acid ( about 15%) and oleic acid ( about 14%). Oxidative stability was studied by using the induction time determined by the Rancimat method. The oil obtained by supercritical fluid extraction (SFE) was less protected against oxidation (4.2 h for SFE-extracted oil and 8.3 h for the pumpkin seed oil extracted with n-hexane). The oil extracted by SC-CO2 was clearer than that extracted by n-hexane, showing some refining. The acidity index was 5.5 for the n-hexane extracted oil. For the oils extracted by SC-CO2, two analyses were made: for the oils obtained at 15 min of extraction time, for which the acidity indices varied from about 15 to 20, and for the remaining oils ( extracted until 150 min), for which the acidity indices varied from about 2 to 2.6. The central composite nonfactorial design was used to optimise the extraction conditions, using the Statistica, version 5, software (Statsoft). The best results, in terms of oil recovered by SC-CO2, were found at 19 MPa, 308 K and a superficial velocity of 6.0 x 10(-4) ms(-1).