Rejection of carotenoids in oil systems by a nonporous polymeric composite membrane

Earlier studies by the authors on crude vegetable oils showed that color compounds are reduced to the extent of 74-80% during membrane processing. In the present study, attempts were made to understand the rejection mechanism of carotenoids using real and model oil systems. In case of model systems consisting of refined high-oleic sunflower (HOSF) oil, lecithin and beta -carotene, the rejection of carotenes was low (11-20%). This could be explained based on the differences between the model and real systems as well as on the solution-diffusion mechanism controlling the material transport across the membrane. This study revealed that beta -carotene did not have affinity for the phospholipid reverse micelles present in the oil. Xanthophylls, the major carotenoids present in the crude soybean oil, were rejected to the extent of 60% in the model system (HOSF oil and lutein). High-performance liquid chromatographic analysis of crude oil revealed that there were few other xanthophylls, which are more polar than lutein. These unidentified xanthophylls would be rejected to a much greater extent by the hydrophobic membrane. The extent of color reduction would depend on the actual composition of xanthophylls present in the crude oil and their relative polarity.