Nalan A. Akgün

Semi-batch operation and countercurrent extraction by supercritical CO2 for the fractionation of lemon oil

Abstract The supercritical fluid extraction of cold-pressed lemon oil was carried out in semi-batch and continuous countercurrent modes. In order to observe the extraction behavior of lemon oil, semi-batch extraction was performed using a rectification column, and the distribution curve for the main constituents of lemon oil was obtained. Separation was improved by applying an internal reflux induced by a temperature gradient along the column. The effects of the reflux on the extraction ratio, the separation selectivity, the concentration factor of each component and the recovery of oxygenated compounds were investigated for continuous operation at pressures of 8.8 and 9.8 MPa. Extraction combined with side-stream withdrawal was useful for lemon oil processing. The continuous operation with a linear temperature gradient from 313 to 333 K at 8.8 MPa showed the highest selectivity. Selectivity increased with the increase in solvent-to-feed (S/F) ratio.

STUDY OF THIN-LAYER DRYING OF GRAPE WASTES

The effect of drying temperature on grape wastes, the solid wastes of the wine and raki production processes, was investigated in a cabinet dryer. Drying experiments were performed three air temperatures of 70°, 90,° and 110°C, at constant air velocity of 1.2 m/s, and initial thickness of 1.8 cm for grape marc and 2.0 cm for grape pulp. Experimental data were fitted to Henderson and Pabis, Page, and logarithmic models, respectively. The performance of these models is evaluated by comparing coefficient of determination and reduced chi-square between the observed and predicted moisture ratios. The statistical analysis concluded that the best model was the logarithmic model. The effective moisture diffusivity varied from 8.55 × 10−10 to 3.32 × 10−9 m2/s over the temperature range. Temperature dependence of the diffusivity was well documented by an Arrhenius-type relationship. The activation energies for grape marc and grape pulp were calculated as 25.41 and 13.74 kJ/mol, respectively.

Supercritical Fluid Extraction of Lavandula stoechas L. ssp. cariensis (Boiss.) Rozeira

Abstract The flowers of Lavandula stoechas L. ssp. cariensis (Boiss.) Rozeira were extracted in both a batch and semi-continuous system by supercritical CO2. In the first stage, experiments were performed in a batch system based on response surface methodology (RSM). Parameters used were pressure, temperature, mixing speed and extraction time, and were coded as, X1, X2, X3 and X4, respectively. These parameters were investigated at three levels (-1,0 and 1). The dependent variable, Y, was taken as the volatile concentrate yield of supercritical fluid extraction. It was calculated with respect to the yield of solvent extraction by dichloromethane. In the second stage, experiments were carried out in a semi-continuous system at constant pressure and temperature, and different CO2 flow rates. Concentrations of volatile components were determined as a function of extraction time and CO2 residence time