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a b s t r a c tSubcritical water extraction was investigated as a novel and alternative technology in the food and pharmaceutical industry for the separation of mannitol from olive leaves and its results were compared with those of Soxhlet extraction. The effects of temperature, pressure, and flow rate of water and also momentum and mass transfer dimensionless variables such as Reynolds and Peclet Numbers on extraction yield and equilibrium partition coefficient were investigated. The operating conditions were: 3-11 MPa, 333-423 K, and water flow rates of 3.3E-9-3.3E-8 m 3 /s. The results revealed that the highest mannitol yield was obtained at 373 K and 5 MPa. However, the extraction of mannitol was not influenced by the variation of flow rate. A mathematical model for mannitol extraction was also developed which predicted the experimental measurements very well. In addition, the results indicated higher extraction yield and lower partition coefficient for the subcritical water extraction in contrast to Soxhlet method.

The experimental feasibility of mannitol extraction from olive leaves using supercritical carbon dioxide was investigated. The experimental data indicated that increasing the pressure from 200 to 350 bar and decreasing the temperature from 80 to 40°C resulted in an enhancement of the extraction yield and reduced the partition coefficient significantly. In addition, increasing the extraction time from 10 to 90 min increased the extraction yield, while further increases up to 180 min did not cause any further change. Ethanol was utilized as an entrainer and the maximum extraction yield was obtained using 20 % of ethanol. Moreover, modeling of the supercritical fluid extraction was carried out with the relevant mass transfer mechanisms involved in the supercritical and solid phases, and the appropriate numerical method of finite difference. The numerical results show that the model with three adjustable parameters is capable of predicting the experimental data very well.

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