Extraction of ginger (Zingiber officinale Roscoe) oleoresin with CO2 and co-solvents:: a study of the antioxidant action of the extracts

The effects of temperature, pressure and the addition of co-solvent (ethanol (EtOH) and isopropyl alcohol (IsoC3), both at 1.17% (mass)) on the kinetics of extraction of ginger oleoresin were studied. The design used was a 2 x 2 x 3 factorial (pressure 200 and 250 bar; temperature: 25 and 35 degreesC; solvent: CO2, CO2 + EtOH, CO2 + IsoC3). The experimental setup used was a fixed bed extractor with diameter of 2.76 x 10(-2) m and length of 0.387 m. The assays were carried out at a mean solvent flow rate of 5.86 x 10(-5) kg/s and with a bed apparent density of 350 kg/m(3). The identification of the substances present in the oleoresin was performed by GC-MS; GC-FID was used to determine the ginger extract compositions. The antioxidant activity of the extract fractions was determined using the coupled oxidation of linolenic acid and beta-carotene. The results show that the temperature and the interaction of the pressure and the solvent significantly affected the total yield. For the mass transfer rate, the effect of the interaction of the pressure and the solvent was significant; the mass transfer rate increased with the pressure in the absence of the co-solvent and decreased when ethanol and isopropyl alcohol were used. The major substances present in the ginger extracts were alpha-zingiberene, gingerols and shogaols; the amounts of these compounds were significantly affected by temperature, pressure and solvent. Nonetheless, the antioxidant activity of the ginger extracts remained constant at approximate to80% and decreased to approximate to60% in the absence of gingerols and shogaols. The Sovovd's model quantitatively described the overall extraction curves. (C) 2002 Elsevier Science B.V. All rights reserved.