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Title: SUPERCRITICAL FLUID EXTRACTION OF EVENING PRIMROSE OIL-KINETIC AND MASS TRANSFER EFFECTS

Author
item King, Jerry
item CYGNAROWICZ-PROVO, MIRIAM - FOOD & DRUG ADM ROCKVILLE
item FAVATI, FABIO - UNIV BASILLICATA, ITALY

Submitted to: Italian Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Supercritical fluid extraction is a processing technique which makes use of highly compressed gases to extract agriculturally-derived products, such as seed oils. Previously we have shown that by using carbon dioxide as the extraction gas, a highly efficient extraction of evening primrose oil can be affected from the seed. Evening primrose oil is used commercially for the treatment of specific diseases and also finds widespread use as nutritional supplement. For this reason, it commands a premium price and, hence, is well matched for the inherently high capital equipment costs required for conducting supercritical fluid extraction. In this research, we have supplemented our previous studies by optimizing and predicting the rates of extraction for evening primrose oil from the ground seed, using both experimentally-derived data and applicable theoretical approaches. From this, data and its treatment and correlation with theory, we optimize the extraction of the oil with respect to time, gas flow rate, and the extraction pressure and temperature. The results from this study have also been compared to existing data on the rate of extraction of the oil on a pilot and production plant scale which exists in the literature, and we have found that our results and correlations agree with those obtained in larger processing facilities. Therefore, the results obtained in this study can be used as a model to scaleup the extraction.

Technical Abstract: For processing utilization, supercritical fluid extraction requires a thorough understanding of the relevant phase equilibria, mass balance, and kinetic factors that impact on the successful recovery of extracts. In this study, we have determined the factors contributing to the kinetics and mass transfer of evening primrose oil (EPO) from its ground seed matrix, to supplement previously determined solubility data and chemical characterization of this oil moiety. The effect of extraction pressure, temperature, fluid density, and flow rate (over a threefold range) have been ascertained; the flow rate effect being correlated in terms of the extracted seed mass and similar data from the literature performed on a pilot and production plant scale. Using a dual mass transfer model, we have correlated the theory with extraction experiments conducted over a pressure range from 20-70 MPa, temperatures from 40-60 deg C, and carbon dioxide flow rates in the interval from 9-27 g/min. The agreement between the model calculations and experimental data is excellent allowing potential use of the data in process design.