Decolorization of vegetable oils by membrane processing

Membrane decolorization studies of chlorophyll
added sunflower oil and crude soybean oil were
conducted in a batch membrane cell using two polymeric
composite membranes (NTGS-2100 and NTGS-1100),
and one polyethylene microfiltration membrane (PE-30).
NTGS-2100 membrane could remove up to 96% and
72% chlorophyll from the undiluted and oil-hexane
(50 wt%) solutions, respectively. Permeate oil flux was
very low when undiluted oil was used as feed, but improved
many fold by diluting with hexane. NTGS-1100
membrane gave higher permeate flux compared to
NTGS-2100, but showed reduced rejection. Absorbance
spectra of crude soybean oil and the permeate in the
350–550 nm range showed a greater degree of decolorization
by polymeric composite membranes. PE-30
membrane showed insignificant rejection of color compounds.
The permeate of conventionally bleached soybean
oil showed a reduction in extinction coefficients at
232 and 270 nm, indicating possible rejection of dienes
and trienes by the composite polymeric membranes. The
membrane process was effective in reducing the color
compounds in crude vegetable oils besides offering
many advantages over the conventional process.