Refined and bleached color

FFA free fatty acids, FAC coior as per Fat Anaiysis Committee, R B refined and bleached color, MID moisture, impurites, and unsaponifiabies. 

Bleaching and color reduction are important in removing contaminants and also in improving the perception of quality in textile sizing applications. For example, the application of bleached tallow or bleached hydrogenated tallow on textile fabrics is preferred over the use of darker fats. When color requirements become important in the use of rendered fats, processors must pay careful attention to raw material selection. An important analysis of the rendered fat is R B color, or refined and bleached color. 

As a result of processing methods, condition of the original byproduct raw material, storage conditions, and other factors, rendered fats may have a minimum color that can be achieved by refining and bleaching. This best attainable color can be determined by the AOCS Method Cc 8d-55, refined and bleached color (tallow and greases for soaps). The various grades of rendered fats reflect different R B color values as outlined by the AFOA (14). 

The fat refining and bleaching operation is carried out to remove impurities that would cause color and odor in the finished soap. The wastewater from this source has a high soap concentration, treatment chemicals, fatty impurities, emulsified fats, and sulfuric acid solutions of fatty acids. Where steam is used for heating, the condensate may contain low-molecular-weight fatty acids, which are highly odorous, partially soluble materials. 

Refined and bleached (R B) color A measure of the amount of red color in the rendered fat is an indicator of the quality of both the starting material and the rendering techniques. This value is measured using the Lovibond 5.25-inch scale according to procedures described in AOCS Official Method Cc 13b 3 (39). The result is referred to as the AOCS Wesson color, the AOCS Lovibond color, or simply Lovibond color. The lower the value, the less colored the sample. 

While safflower oil may, on occasion, display minute traces of a fine, lacy wax (101), most U.S. refiners neither winterize nor dewax safflower oil, feeling that a brilliant oil can be delivered without it. Japanese refiners generally insist on refining and bleaching safflower oil to under 1.0 red color, followed by winterization to avoid problems with minute amounts of wax that may appear in the oil in the winter months in the north. 

Figure 7. Effect of oxidation (aeration at 120°C) on the color of refined and bleached cottonseed oil.

The industrial uses of the different fats depend on the characteristics of such fats as determined by analyses such as titer, fatty acid profile, free fatty acid content (or sometimes acid value), saponification value, refined and bleached (R B) color, peroxide value, and by the absence of impurities, such as moisture and unsaponi-fiable matter. Some abbreviations may be used, such as FFA for free fatty acids and IV for iodine value. 

The oil chemists have avoided the more serious of these difficulties by alternative methods, using F.A.C. Standards, for example, for different hues. Melvin, et al. (1953) have studied the spectral characteristics of green soybean oil and have suggested optical density values at selected wave lengths which would delimit Grade 2 for crude, refined, refined and bleached oils. Thomson (1953) has further discussed single-number systems with particular reference to the measurement of color of cottonseed and soybean oils. 

After refining (neutralization), the oil is bleached. Color bodies in the oil are adsorbed on the surface of the bleaching clay and activated carbon particles. Experiments cited by Brimberg (19) showed that bleaching process follows the rate formula. In (c/cq) = —ky/i, where t is the time from the addition of bleaching clay c is the concentration of pigment at time t, cq is the concentration at to, and k is the rate constant. 

Overcooking lowers the nutritional quality of the meal and darkens both the oil and the meal. Poor-quality seeds with high levels of free fatty acids cannot be cooked for as long a period as high-quality seeds because of darkening. Darker oil requires additional refining to achieve the desired bleach color. 

Safflower seed that is produced in areas with late summer rains or cool weather cycles that interfere with maturation can produce dark-colored or greenish oils that are often higher in FFA as well. If the seed has sprouted before or during harvest or has been attacked by Alternaria, Pseudomonas, or other head-rot diseases, the resulting oil can be quite difficult to refine and extremely difficult to bleach. 

Refinery Bleach. Various bleaching clays purify and remove color bodies from refined oils. These wastes contain 5% to 35% oil. The characteristics of these materials are such that they will combust spontaneously, which has created problems for disposal in sanitary landfills, as well as at factory locations in some instances, but this condition can be overcome by several methods. The model refinery presented in the previous section will generate about 2500 kg of waste earth per day, of which 570 kg is oil. 

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