Drying oils free fatty acid content

It should be noted that two ways are used to express the excess caustic soda. In American refineries the excess is expressed in terms of dry sodium hydroxide on a percentage basis, calculated on the weight of oil. In most other refineries the excess is stated as a percentage of the weight or volume of the caustic soda solution stoichiometrically equivalent to the free fatty acid content of the oil. The latter method is used in this chapter. 

Commercial lecithin is produced by water degumming (precipitation from oil with ion-exchange treated water), separation by stacked disk centrifuge, and vacuum drying to less than 1 percent moisture content. Crude lecithins contain 70-72 percent acetone insolubles (AI) and are standardized to 62-64 percent and an acid value of 30 by addition of oil and fatty acids before sale. Crude lecithins may be treated with acetone to obtain free-flowing powders with 95-98 percent AI. Lecithin can be additionally purified, bleached, fractionated, hydrogenated, hydrox-ylated, acetylated, sulfonated, and halo-genated.104 One domestic company makes 13 kinds of lecithin for food uses alone. 

Several methods exist for deacidification of fat or oil. The choice depends on the amount of free fatty acidspresent in crude fat or oil. The removal of fatty acids with 15% sodium hydroxide (alkali refining) is the most frequently used method. Technically, this is not very simple since fat hydrolysis has to be avoided and, moreover, the sodium soap (the soap-stock ), which tends to form stable emulsions, has to be washed out by hot water. After vacuum drying, the fat or oil may contain only about 0.05% free fatty acids and 60 to 70 ppm of sodium soaps. When the fat or oil is treated with diluted phosphoric acid, the content of sodium soaps decreases to 20 ppm and part of the trace heavy-metal ions is removed. 

Fluidizing. Fluidizing additives such as soybean oil, fatty acids, or calcium chloride can be added to adjust the viscosity. The viscosity of dried crude lecithin can also be decreased by warming it to a maximum of 60°C. The dried crude lecithin product (unbleached or bleached) can also be used to prepare a variety of grades of lecithin by removing the oil to increase the phospholipid content, or by separating the oil-free lecithin into alcohol-soluble and alcohol-insoluble fractions. 

Because calcium salts of fatty acids are insoluble in the rumen, they are partly protected against biohydrogenation (76). Therefore, it is logical, although untested, to assume that feeding calcium salts of CLA to ruminants would result in less conversion of CLA to stearic acid in the rumen than would feeding the free fatty add form of CLA this result would make CLA from the dietary caldum salt of CLA more available for absorption from the intestine. A study was conducted at Iowa State University to determine the effect of feeding CLA as a free add and as a calcium salt on CLA content of milk (77). The six different diets, with suppl ental fat concentrations expressed on a dry matter basis, for Holstein cows were as follows (i) control, (ii) control + 5% soy oil, (iii) control +1% CLA as CLA-60, (iv) control +1% CLA + 4% soy oil, (v) control +1% Ca(CLA)2, and (vi) control + 1% Ca(CLA)2 + 4% soy oil. 

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