EXTRACTION OF OIL FROM GRAPE SEEDS WITH SUPERCRITICAL CARBON DIOXIDE
INTRODUCTION Grape seeds are known as a waste byproduct of juice and wine production. They contain oil between 10 and 20%, depending on grape variety, which has high amounts of unsaturated fatty acids, usually linoleic and oleic acids ranged from 53 to 78% and 16 to 31% (Bail et al., 2008; Sabir et al., 2012). Oil from grape seeds is also constituted with natural antioxidants, among others, tocopherols in the 50 to 520 mg/kg range that are responsible for health-benefits such as lowering cholesterol levels and alleviating cardiovascular diseases (Bail et al., 2008; Sabir et al., 2012). Grape seed oil is a promising lipid for human consumption due to its nutritional constituents. The use of supercritical carbon dioxide (SC-CO2) is an effective method for oil extraction. It produces purer oil and preserves bioactive components of the oil when compared with the typical hexane extraction and refining. This is because the low critical point (Pc = 7.3 MPa, Tc = 31°C) and characteristics of CO2 that allows for organic solvent free extraction, making it safe and efficient for separation and fractionation of thermally sensitive oils (Agostini et al., 2012). In the present study the effects of pressure (20, 30 MPa) and temperature (30 °C, 40 °C, 50 °C) were investigated on the oil yield. The quality of SC-CO2 extracted oil in term of fatty acid content was compared to that of hexane-extracted oil.
The fatty acid and tocopherol constituents of the seed oil extracted from 21 grape varieties (Vitis spp.).
BACKGROUND
Fatty acids and tocopherols in appropriate quantities are invaluable attributes that are desirable in seeds of agricultural products. Studies have generally focused on the evaluation of the oil and tocopherol components of oil crops. Recently, investigations revealed that the grape seed has robust potential in the production of healthy fatty acids as well as tocopherols. This study was thus conducted to determine the oil and tocopherol components of grape seeds, obtained from various grape cultivars of different species, including two rootstock varieties.


RESULTS
The grape seed oil concentration of the studied varieties ranged from 7.3 to 22.4%. The determined fatty acid profiles of the genotypes conformed to the pattern described in the literature for grapes. Linoleic acid is the major component comprising 53.6-69.6% of the total, followed by oleic (16.2-31.2%), palmitic (6.9-12.9%) and stearic (1.44-4.69%). The oils of all the seeds analysed showed a preponderance of α-tocopherol (ranging from 260.5 to 153.1 mg kg⁻¹ oil extract). β-Tocopherol, γ-tocopherol and δ-tocopherol were also detected with the general means of 0.98, 22.2 and 0.92 mg kg⁻¹, respectively. Linoleic acid showed a significantly negative correlation with all the fatty acids analysed. The strongest negative correlation existed between linoleic and oleic acids (r = -0.834, P < 0.01).


CONCLUSION
Present investigations indicated that oil content, fatty acid composition and tocopherol constituents of grape seed show great variation among the genotypes. Markedly higher proportions of linoleic acid with considerable amounts of tocopherols found in the oil samples suggest that grape seed is a good source for culinary, pharmaceutical and cosmetic uses.
Yield and composition of grape seed oils extracted by supercritical carbon dioxide and petroleum ether: varietal effects.
Grape seed has a well-known potential for production of oil as a byproduct of winemaking and is currently produced as a specialty oil byproduct of wine manufacture. Seed oils from eight varieties of grapes crushed for wine production in British Columbia were extracted by supercritical carbon dioxide (SCE) and petroleum ether (PE). Oil yields by SCE ranged from 5.85 +/- 0.33 to 13.6 +/- 0.46% (w/w), whereas PE yields ranged from 6.64 +/- 0.16 to 11.17 +/- 0.05% (+/- is standard deviation). The oils contained alpha-, beta-, and gamma-tocopherols and alpha- and gamma-tocotrienols, with gamma-tocotrienol being most important quantitatively. In both SCE- and PE-extracted oils, phytosterols were a prominent feature of the unsaponifiable fraction, with beta-sitosterol quantitatively most important with both extractants. Total phytosterol extraction was higher with SCE than with PE in seven of eight variety extractions. Fatty acid composition of oils from all varieties tested, and from both extraction methods, indicated linoleic acid as the major component ranging from 67.56 to 73.23% of the fatty acids present, in agreement with literature reports.