Adsorption of lutein from soybean oil on silicic acid I. Isotherms

Adsorption of lutein from crude soybean oil miscella on dispersed silicic acid resulted in three different Freundlich type isotherms, depending on the amount of adsorbent used. Normally, changing the amount of adsorbent gives a new point on the same isotherm. Further investigation of the lutein adsorption revealed that addition of 1% isopropanol to the hexane solvent and deactivation of the silica acid with water decreased lutein adsorption. Purification of the lutein resulted in increased adsorption, indicating that triglyceride was competing for adsorption sites. The triglyceride competition was confirmed by calculating an adsorption isotherm for triglyceride from crude soybean oil miscella. Use of silicic acid as a column rather than dispersed yielded multiple isotherms for lutein adsorption based on the amount of adsorbent used. Also, lutein adsorption on columns was concentrated at the entrance to the column. Experiments showed that lutein adsorption was not due to partitioning between bound triglyceride and hexane solvent.