EFFECTS OF PLASMA-MODIFIED POLYVINYLIDENEFLUORIDE AND POLYETHERSULFONE ULTRAFILTRATION (UF) MEMBRANE TREATMENTS ON QUALITY OF SOYBEAN OIL

The effects of unmodified and surface-modified polyvinylidenefluoride (PVDF) and polyethersulfone (PES) ultrafiltration membranes on quality of crude soybean oil and crude oil miscellas were studied. Membranes were modified with hexamethyldisiloxane in radiofrequency plasma polymerization (PlzP) at 60 W (PVDF) or 75 W (PES) glow discharge power for 5 min. Contact angle results indicated an interfacial free energy increase between water and solid surface by 2.1- and 12.7-fold for PVDF and PES, respectively, after PlzP, i.e., both membranes became more hydrophobic. Modified PVDF removed 10% more free fatty acids, 8-11% peroxides, and maintained 2-5% more tocopherols compared to those of unmodified PVDF and modified PES. Oxidation products and color compound removal of modified PVDF from crude oil and miscellas were similar to the commercial bleaching step and better than degumming-neutralization step. Total tocopherol loss during modified PVDF treatment was 5.3% and 5.0-6.8% for crude oil and miscellas, respectively, and these values were far below than any processing steps in commercial refining (10.4-28.4% loss).