Supercritical carbon dioxide extraction of bergamot peels. Extraction kinetics of oil and its components

Bergamot flavedo (Citrus bergamia Risso) was extracted by supercritical carbon dioxide (SC-CO2) at three different conditions: 80 bar of pressure at 40°C of temperature, 90 bar at 50°C, 100 bar at 60°C. The density value was similar for every experiment and was limited between 282 and 288 g/dm3. The extractions were performed on fresh and dried minced peels. The extraction curves showed two phases of the process. The first part had a constant oil concentration in the SC-CO2 procedure, with the slope of the line influenced by the temperature. The second extraction part showed that the concentration of the oil in the solvent is limited by diffusion and the oil yield has a small increase during the extraction. The asymptotic value was reached at ms:m0 ratio of 12–14 (ms:kg of CO2 utilized; m0:kg of matrix charged). In addition, the composition of the extracts changed during the process. Therefore, in the first period a high concentration of hydrocarbon monoterpene was observed; after an appropriate extraction time, the composition of the volatile fraction was similar to that typical bergamot essential oil. Bergaptene content in the samples was also quantified and increase of its percentage during the extraction was observed. The bergaptene solubility was influenced by the water content of the matrix, so a higher percentage of this compound was found in extracts obtained from fresh bergamot peels.