Edible oils membrane processing

The commercial membrane separation processes are offered in the areas of nitrogen production and waste treatment applications (1). Developing membrane applications in oil milling and edible oil processing are (1) solvent recovery, (2) degumming, (3) free fatty acid removal, (4) catalyst recovery, (5) recovery of wash water from second centrifuge, (6) coohng tower water recovery, (7) protein purification, and (8) tocopherol separation. 

Lipid peroxidation is a problem not only in the edible oil, but also in the human body. Excess production of oxygen radical species and particularly hydroxyl radicals can affect lipid cell membranes to produce lipid peroxides and reactive oxygen species (ROS), which are linked to a variety of diseases, such as cancer and cardiovascular disease, and acceleration of the aging process. 

Membranes have also been integrated at a second stage in edible-oil processing to recover the extraction solvents. Koseoglu reported the use of RO and UF in the separation of cotton-seed oil from isopropanol, ethanol and hexane. These membranes, originally developed for aqueous applications, showed acceptable performances in isopropanol and ethanol, but were often damaged or hardly permeable, as in the case of hexane [28]. Schmidt tested a PDMS membrane in the separation of corn-seed oil from hexane, with high permeability and rejection values of 90%... 

As weU as in edible-oil processing, the use of organic solvents is also relevant in the synthesis of amino adds and their derivatives. In producing dipeptides such as L-aspartyl-L-phenylalanine methyl ester, better known as aspartame, from amino acids and derivatives via enzymatic processes in organic solvents such as butyl acetate and 2-methyl-2-butanol, unreacted amino acids should be recycled after the synthesis to make the process more efficient. Reddy et al. tested several commercial membranes and found a polyamide-polyphenylene sulfone composite to be promising for this appHcation. However, further research is stiU needed here to apply other membrane materials, which are more resistant towards solvents like butyl acetate [33]. 

The recovery of a solvent in the processing of vegetable oils is done mainly by evaporation, with vapors recovered from noncondensable gases by absorption in mineral oil. For economic, environmental, and security reasons, make the recovery of a solvent in the most critical steps in the processing of edible oils. The first reverse osmosis membranes... 

Fig. 34.23. Principle of membrane-type filtration of olein and stearin. (From Tirtiaux, A., in World Conference Proceedings, Edible Fats and Oils Processing Basic Principles and Modern Practices, D. R. Erickson (Ed.), pp. 136-141, AOCS, Champaign, IL, 1990. With permission.)...

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