Characterization of phospholipid reverse micelles in nonaqueous systems in relation to their rejection during membrane processing

The phospholipid (PL) rejection mechanism during membrane degumming was evaluated based on its critical micelle concentration (CMC) levels in undiluted and hexane-diluted vegetable oils. In this context, the influence of PL composition and solvent medium on the CMC levels has been investigated. In real and model systems, higher phosphatidylcholine to PL ratio lowered the CMC value and vice versa. The CMC of PL was lower in hexane-diluted systems when compared to undiluted oil systems owing to the greater hydrophobic-repulsive forces between hexane and amphiphilic PL. The PL rejection by UF membrane was near complete when the PL content of system was above CMC. Among the systems with lower PL contents (< CMC), rejection was greater in hexane-diluted systems (82–99% in lecithin-hexane system) than in undiluted oil systems (~ 40% in sunflower oil) owing to greater concentration polarization effect responsible for reverse micelle formation at the membrane surface leading to their subsequent rejection. UF membranes are generally preferred owing to higher productivity and the results suggest that their rejection performance could be kept high by careful manipulation of initial PL content. Nonporous membranes were effective in degumming vegetable oils irrespective of initial PL content and the type of system.