STUDY ON THE PILOT-SCALE EXTRACTION OF ONION OLEORESIN USING SUPERCRITICAL CO2

Supercritical carbon dioxide (SC-CO2) was used to produce oleoresin fr om dried onion by pilot-scale extraction. The results showed that the extraction pressure and temperature affected the yield and sulphur con centration of onion oleoresin. Increase of the temperature from 45 to 65 degrees C at 300 bar resulted in an increase of the yield and the s ulphur concentration of oleoresin. At the same temperature (45 degrees C) the yield was also higher at 300 bar than 100 bar while sulphur co ncentration of oleoresin got smaller at 300 bar than at 100 bar. The v olatile composition of oleoresin displayed practically no differences as a function of extraction parameters, Comparison of different extrac tion methods showed that the yield after SC-CO2 extraction was 22 time s higher than that after steam distillation, but it was 14 or 39 times less than that after alcohol extraction, shaking at 25 degrees C or i n Soxhlet apparatus, respectively. The concentration of sulphur was th e highest in steam distilled onion oil while it was the lowest in the extract of hexane and alcohol (at 25 degrees C). The results of sensor y evaluation showed that oleoresin extracted by SC-CO2 was the first i n ranking (at level of significance 0.05), before steam distilled oil and alcoholic extract. There was no significant difference between ste am distilled oil and alcoholic extract in ranking, but the alcoholic e xtract was the least desirable, since the intensity of its off odour a ttribute was the highest. (C) 1998 SCI.