Membrane Technology in Degumming, Dewaxing, Deacidifying, and Decolorizing Edible Oils

Abstract

A membrane process offers several advantages over the conventional method of oil refining. Conceptually, membranes could be used in almost all stages of processing. In the present review, various attempts made by the researchers towards degumming, dewaxing, deacidifying, and decolorizing edible oils using membrane technology with and without using solvents have been discussed. Attempts made with UF and nonporous membranes have demonstrated the ability of these membranes to separate phospholipids from undiluted and hexane-diluted oils and a high oil flux was obtained with UF membranes in hexane-diluted oils. MF membranes were very effective for dewaxing undiluted oils while UF membranes were effective in dewaxing hexane-diluted oils without a precooling step. Deacidification was successful only with either addition of an alkali followed by membrane filtration or by following an indirect route of selective solvent extraction of FFA followed by membrane separation. Consistent color reduction in terms of pigments (chlorophyll and xanthophylls) and other instrumental measurements (Lovibond and visible spectra) could be achieved only with nonporous membranes. Interestingly, these membranes did not have selectivity for α-and β-carotenes. UF membranes are best suited for degumming and dewaxing applications, while nonporous membranes appear to be a better choice for achieving simultaneous degumming, dewaxing, and decolorization of oils. Hexane-dilution improved the oil flux of nonporous membranes by one order of magnitude, but further improvement is desirable for industrial adoption.

Keywords:

• bleaching
• deacidifying
• degumming
• dewaxing
• edible oils
• membrane processing

ACKNOWLEDGEMENTS

S. Manjula thanks the Council of Scientific and Industrial Research, New Delhi, India for the award of CSIR-JRF Fellowship.

Notes

^a Solvent free basis.

^b Percent retention.

^c Not reported/inadequate data for calculation.

^d Wax and gum (acetone insolubles).

^e Effective reduction based on PL content of crude oil.

^a Solvent-free basis.

^b Not reported/inadequate data for calculation.

^c Wax and gum (acetone insolubles).

^a Solvent free basis.

^b Percent reduction of FFA in oil.

^c Not reported/inadequate data for calculation.

^d FFA content in methanol.

^e Percent rejection of FFA from alcohol extract.

^f Methanol flux.

^a Solvent free basis.

^b Percent reduction in carotenoids/Lovibond color value (5R+Y).

^a Solvent free basis.

^b Percent retention.

^c Not reported/inadequate data for calculations.