Refining of crude lecithin using dense carbon dioxide as anti-solvent

Gas anti-solvent crystallization (GASC) has been utilized for refining of crude lecithin (L) from its solution in hexane (H) with dense carbon dioxide as the anti-solvent, leaving behind its oil in the solution. The performance of the process has been evaluated in terms of the lecithin content and its recovery in the final solid product. The effects of various process parameters have been analyzed at temperatures in the range of 283-313 K, pressures in the range of 15-80 bar, initial oil in crude lecithin in the range of 20-60 wt.% and hexane in the feed solution in the range of 80-95 wt.%. The crystallization of lecithin is facilitated by a drastic reduction of its solubility in hexane solution due to CO2 dissolution which varied in the range of 40-75 wt.% CO2 at temperatures in the range of 283-313 K. However, any phase separation of oil was avoided which occurred with more than 63 wt.% CO2 in the solution. The highest value of selectivity of lecithin (defined as the ratio of the wt.% ratios of lecithin and oil in the product to that in the feed solution) was observed at 298 K and 65 bar for a complete (100%) recovery lecithin, and the selectivity decreased on lowering the temperature to 283 K. At any temperature, crystallization of lecithin occurred over a range of pressure or a range of CO2 dissolution, allowing different combinations of enrichment and recovery of lecithin from the feed solution. The highest enrichment in the product was 98.6 wt.% lecithin with 78% recovery and this could be obtained at 298 K and 58 bar, starting from the crude lecithin feed having 60 wt.% oil. For a lower initial oil content, even a lower pressure was required to obtain a final solid product having the same lecithin content. Also, the lecithin content in the final product increased with an increase in the hexane-to-feed ratio, as oil remained miscible in the excess hexane. (C) 2003 Elsevier B.V. All rights reserved.