Liquid-Liquid Equilibrium Data for the System Corn Oil + Oleic Acid + Ethanol + Water at 298.15 K Cintia B. Gonc ¸ alves, Eduardo Batista, and Antonio J. A. Meirelles* LASEFI, Faculty of Food Engineering, State University of Campinas (UNICAMP), P.O. Box 6121, Zip Code 13083-970 Campinas, SP Brazil Deacidification of vegetable oils can be performed by liquid-liquid extraction. The present paper reports experimental data for the system corn oil + oleic acid + ethanol + water at 298.15 K and different water contents. The addition of water to the solvent reduces the loss of neutral oil in the alcoholic phase and improves the solvent selectivity. The experimental data were correlated by the NRTL and UNIQUAC models, with a global deviation of 0.89% and 0.92%, respectively. Introduction Crude vegetable oils consist predominantly of triacylg- lycerols and free fatty acids, with mono- and diacylglycerols also present at a lower level. They are obtained mainly by solid-liquid extraction from oil seeds using hexane petro- leum fractions as solvent. 1,2 The refining processes of crude vegetable oils involve solvent stripping, degummimg, bleach- ing, deacidification, and deodorization. 3,4 The removal of free fatty acids (FFAs) is the most important stage of the purification process of oils, mainly because the yield of neutral oil in this operation has a significant effect on the cost of refining. 5 Besides, the presence of these compounds can adversely affect oil quality and stability to oxidation. Deacidification of oils is usually performed by chemical or physical refining. However, for oils with high acidity, chemical refining causes high losses of neutral oil due to saponification and emulsification. Physical refining is also a feasible process for deacidification of highly acidic oils, since it results in less loss of neutral oil than the traditional process, but more energy is consumed. Moreover, in some cases, the refined oil is subject to undesirable alterations in color and a reduction of stability to oxidation. 6 Thus, it is important to develop alternative processes for the deacidification of edible oils. The deacidification of oils by liquid-liquid extraction using an appropriate solvent has been receiving attention because of its advantages in comparison to the physical and chemical refining. Kale et al. 7 studied the deacidifi- cation of crude rice bran oil by extraction with methanol. Turkay and Civelekoglu 8 investigated the liquid-liquid extraction of sulfur olive oil miscella in hexane with aqueous ethanol solutions. As this process is carried out at room temperature and atmospheric pressure, less energy is consumed and the oil is submitted to softer treatments. Besides, the liquid-liquid extraction has the advantages of avoiding the formation of waste products and reducing the loss of neutral oil. Furthermore, solvent stripping from refined oil and solvent recovery from the extract stream can be easily carried out, because of the high difference between the boiling points of the solvent, fatty acids, and triacylglycerols. In fact, these operations can be accom- plished by evaporation or distillation at relatively low temperatures, in most cases lower than 353.15 K. 9 Liquid-liquid equilibrium data for systems containing vegetable oils and fatty acids are relatively scarce in the literature, yet such information is essential for studying the deacidification of edible oils by solvent extraction. The present paper reports liquid-liquid equilibrium data for the system corn oil + oleic acid + ethanol + water at 298.15 K and different water contents. The addition of water to the solvent reduces the loss of neutral oil and improves the solvent selectivity. 9 The experimental data set was used for adjusting the parameters of the NRTL and UNIQUAC models. Material Refined corn oil of the Mazzola brand (Brazil) was utilized as a source of triacylglycerols, and commercial oleic acid of Riedel-deHaen as the source of fatty acids. The chemical composition of these reagents was determined by gas chromatography of fatty acid methyl esters (these data are published in ref 10). Corn oil contains 12 different isomer sets with molecular weights varying in the range (831.35 to 887.46) g/mol. The commercial oleic acid contains 83.13 mass % oleic acid, 5.82 mass % palmitoleic acid, 5.05 mass % linoleic acid, 4.05 mass % palmitic acid, and linonenic, stearic, and myristic acids as minor components. The average molecular weight was 872.61 g/mol for the corn oil and 278.59 g/mol for the commercial oleic acid. The solvent used was ethanol, from Merck, with purity greater than 99.5%. Distilled water was used to obtain the aqueous solvent at different water contents (5, 8, 12, 18 wt %). Experimental Procedure Equilibrium cells similar to those of Silva et al. 11 were used for the determination of liquid-liquid equilibrium data. The cell temperature was controlled with a thermo- static bath (Cole-Parmer, Model 12101-15, accurate to 0.1 K). Thermometers (Cole-Parmer Instrument Co.) with subdivisions of 0.1 K were used for monitoring the cell temperature. The component quantity was determined by weighing on a Sartorius analytical balance (Model A200 S, accurate to 0.0001 g). The mixture was stirred vigorously with a magnetic stirrer (FISATOM, Model 752A) for 20 min * To whom correspondence should be addressed. E-mail address: tomze@ceres.fea.unicamp.br. Fax number: + 55-19-788-4027. 416 J. Chem. Eng. Data 2002, 47, 416-420 10.1021/je010273p CCC: $22.00 © 2002 American Chemical Society Published on Web 03/01/2002