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.
Characterisation of various grape seed oils by volatile compounds, triacylglycerol composition, total phenols and antioxidant capacity.
Grape seed oil (Oleum vitis viniferae) representing a promising plant fat, mainly used for culinary and pharmaceutical purposes as well as for various technical applications, was subject of the present investigation. HS-SPME-GC-MS was applied to study volatile compounds in several seed oil samples from different grape oils. The triacylglycerol (TAG) composition of these oils was analyzed by MALDI-TOF-MS/MS. In addition the total phenol content and the antioxidant capacity (using TEAC) of these oils were determined. The headspace of virgin grape oils from white and red grapes was dominated by ethyl octanoate (up to 27.5% related to the total level of volatiles), ethylacetate (up to 25.0%), ethanol (up to 22.7%), acetic acid (up to 17.2%), ethyl hexanoate (up to 17.4%) and 3-methylbutanol (up to 11.0%). Triacylglycerol composition was found to be dominated by LLL (up to 41.8%), LLP (up to 24.3%), LLO (up to 16.3%) and LOO (up to 11.7%), followed by LOP (up to 9.3%) and LOS/OOO (up to 4.3%). Total phenol content ranged between 59μg/g and 115.5μg/g GAE. Antioxidant capacity (TEAC) was analyzed to range between 0.09μg/g and 1.16μg/g.
Chemical characterization and phase behaviour of grape seed oil in compressed carbon dioxide and ethanol as co-solvent
The aim of this work is to report phase equilibrium experimental results for the systems grape oil/carbon dioxide and (grape oil/carbon dioxide + ethanol). The oil was obtained by supercritical extraction from the grape seed residue from wine production. The static synthetic method using a variable-volume view cell was employed for obtaining the experimental bubble and dew (cloud) points transition data over the temperature range of (313.15 to 343.15) K and pressures up to 20.6 MPa. The experiments were carried out using (ethanol + CO2) overall mass fractions ranging from 0.50 to 0.99, keeping a fixed ethanol to carbon dioxide molar ratio at 1:3. Results indicate the existence of complex phase behaviour for all temperatures investigated with the occurrence of vapour–liquid, liquid–liquid and vapour–liquid–liquid phase transitions observed.