Application of membranes and enzymes in processing vegetable oils

Manjula, S. (2009) Application of membranes and enzymes in processing vegetable oils. PhD thesis, University of Mysore.

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Abstract

The thesis was initiated through an exhaustive review of research conducted worldwide towards degumming, dewaxing, decolourizing and deacidifying edible oils using membrane technology. To begin with, the influence of phospholipid (PL) composition and solvent (hexane) medium on critical micelle concentration levels in crude oil and crude oil-hexane systems was investigated, which explained the dependency of ultrafiltration membranes on the initial PL concentration in their degumming performance and how the nonporous membranes achieved near complete degumming in vegetable oils under various conditions. Attempts made to enhance oil flux showed that the nonporous membrane did not reject triglycerides (TG) over a wide range of hexane dilution due to a positive flow coupling with hexane while improving the oil flux by an order of magnitude. Besides, the results revealed that the oil flux followed an inverse relationship with average molecular weights of TG despite their narrow range of existence in various vegetable oils, interestingly even under hexane-diluted conditions. Assessing the potential of nonporous membranes revealed its prospect as a single-step pretreatment process for simultaneous degumming, dewaxing and decolourizing crude rice bran oil besides eliminating the problem causing phosphoglycolipids. Enzymatic degumming employing phospholipase-A1 was found to be effective in oil system, however only to a moderate extent in hexane-oil system. Further, potential applications of membrane technology in nonaqueous systems were examined, specifically for enriching beneficial oryzanol in rice bran oil (RBO) and deoiling lecithin. Nonporous membrane exhibited moderate rejection of oryzanol (ferulate esters) in RBO owing to their hydrophilic nature, suggesting 8 a physical method for enriching oryzanol in RBO and thereby the possibility of producing a standard RBO with a guaranteed oryzanol content. The phenomenally high selectivity of nonporous membrane for PL was responsible for its high efficacy in deoiling lecithin in a favourable solvent (hexane) scoring over the industrially-practiced acetone-extraction method. Nonporous membranes possess the potential for being employed in various steps of vegetable oil processing, however the flux needs further improvement for industrial adoption. Thus present study has clearly brought out the effectiveness of nonporous membranes on their suitability in nonaqueous applications, principally in vegetable oil processing.

Item Type:	Thesis (PhD)
Uncontrolled Keywords:	Edible oils-; Degumming; Dewaxing; Decolorizing; Deacidifying; Membrane technology; Enhancing of oil flux; RBO
Subjects:	600 Technology > 08 Food technology > 05 Processing and Engineering 600 Technology > 08 Food technology > 19 Lipids-oils/fats
Divisions:	Food Engineering
Depositing User:	Food Sci. & Technol. Information Services
Date Deposited:	12 Mar 2010 10:53
Last Modified:	12 Mar 2010 10:53
URI:	http://ir.cftri.res.in/id/eprint/9386

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