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

Abstract

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 β-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 β-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.Paper no. J9845 in JAOCS 78, 803-807 (August 2001).

Processing vegetable oils using nonporous denser polymeric composite membranes

“…But the greater reduction of color values observed in screw-pressed oils (18) revealed that the solution-diffusion effect was the predominant mechanism in rejecting pigments. It seems that the silicon layer of the membrane did not have higher permeability for xanthophylls, resulting in greater rejection in crude oils (21). HOSF oil along with a lutein and lecithin model system.…”

“…Xanthophylls (predominantly lutein) were detected in mature soybean seeds, whereas no hydrocarbon carotenoids including β-carotene were detected (except for a trace amounts in some varieties) (32). Xanthophylls are the major carotenoids present in the oils extracted from soybean and rapeseed (21).…”

“…The following systems were studied to understand the rejection phenomenon of carotenoids (21). High oleic sunflower (HOSF) oil along with β-carotene and lecithin model system.…”

“…Sorption plays a major role in determining the selectivity since the difference in diffusivity of components is generally smaller in liquid systems (27). Therefore, it can be construed that actual feed composition and thermodynamic interactions between the components in the ternary system resulted in lower positive rejection instead of preferential permeation of carotenes (21).…”

“…In recent years, Subramanian et al (15)(16)(17) extensively investigated processing solvent-extracted oils, screw-pressed oils (18), and used frying oils (19) with nonporous denser polymeric composite membranes. Studies were also carried out to understand the rejection mechanism of phospholipids (20) and pigments (21), as well as differential permeation of liquid constituents, namely, TG, FFA, and tocopherols (22,23). In this review, attempts are made to explain the results obtained in these studies with real and model systems in a batch membrane cell, focusing on the mechanism of rejection or differential permeation of oil constituents during processing using nonporous denser polymeric composite membranes (Table 1).…”