Refining physical

Leon-Camacho, M., Ruiz-Mendez, M.V., Graciani-Constante, M., Graciani-Costante, E. (2001) Kinetics of cis-trans isomerization of linoleic acid in the deodorization and/or physical refining of edible fats. Eur. J. Lipid Sci. Technol., 103, 85-92. 

The term row crop in this chapter generally means annual crops that are grown in rows. Their seeds have many similarities in extraction and oils processing, and often can be handled in the same facilities if provision is made for differences in dehulling requirements. As a group, these oils contain appreciable amounts of phosphatides, which must be removed, and are not as readily processed by physical refining as tree seed pulp crops such as palm and olive oils instead, they must be prepared for lower temperature deodorization. 

In processing most oilseeds, hexane is stripped from the miscella by distillation to produce a crude oil that subsequently is alkali or physically refined. However, gossy-pol and other pigments become extremely difficult to bleach if left in warm cottonseed oil for more than a few days. It is normal practice for cottonseed oil mills to send their crude oil immediately to an alkali refinery or to operate an on-site miscella refinery, where phosphatides, FFA, and color pigments are removed by alkali treatment of the oil-extraction solvent mixture. Cooling the crude oil as produced, until refining, also slows fixing of color. 

Deodorization is the final step in the production of RBD oils and modified fats. The process is called deodorization if most of the FFA is removed by alkali neutralization as with row crop ( soft ) oils, and physical refining if,... 

The organic and natural foods markets demand nonchemically treated oils. These often are made by hard pressing the source and water degumming the oil, followed by bleaching with natural (nonchemically treated) earths and removing FFA by physical refining. 

Warner, K., The effect of expeller pressed/physically refined soy oil on flavor of french fried potatoes and frying oil stability. USDA/ARS National Center for Agricultural Utilization Research. Peoria, IL. (Presented at AOCS Annual Meeting, May 9-12, 2004, Cincinnati, OH.)... 

Deodorization/Physical Refining Quality control is especially concerned with flavor, free fatty acid concentration, color, stability, and trace contaminants. With respect to routine flavor testing, two-three trained panelists test the flavor of small sample of the oil. The oil must be essentially bland, but very slight beany or grassy notes are tolerated. Free fatty acids, color, and stability testing is done by the AOCS official methods (76). 

Refining of crude fats and oils involves a series of steps for the removal of impurities from the glycerides to make the product suitable for human consumption and improve product shelf life. The impurities are fatty acids, phosphatides, metal ions, color bodies, oxidation products, solid paricles, and volatiles that include objectionable odors. Crude coconut oil is refined by any of the following methods (1) chemical refining (batch or continuous) and (2) physical refining. The comparative performance of both methods is summarized in Figure 4. 

Figure 4. Material balance chemical and physical refining of crude coconut oil. Units were converted from the original lb. and Be to kg. and sp. gr. (18).

Design and technological breakthroughs have improved efficiency of the system. Performance of new packed-column deodorizers for physical refining is predicted by computer calculation, for which a special program has been developed on the basis of experience with earlier columns (22). 

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