The effects of both preparation method and season on the supercritical extraction of ginger

Experiments were conducted to study and compare the supercritical extraction of oleoresin from fresh, oven-dried and freeze-dried ginger samples. When new season water-rich fresh ginger rhizomes were utilised, higher extraction yields resulted relative to both the oven-dried and freeze-dried samples. Mathematical modelling of experimental data confirmed that this yield enhancement resulted principally from an enhancement in the effective diffusivity within the ginger particle. However, when a more fibrous and less moist old season ginger supply was utilised, the mass transfer rate in all samples declined. Further, the reduction in effective diffusivity was most pronounced for the fresh ginger sample. HPLC analysis showed that the ginger extract obtained from the oven-dried feed contained proportionately less gingerols and more shogaols due to thermal degradation. This confirms that the utilisation of fresh ginger rhizomes for supercritical extraction would lead to a more pungent and naturally flavoured extract. However, there are a number of significant disadvantages to this approach from a manufacturing perspective that would need to be considered. (c) 2005 Elsevier B.V. All rights reserved.