The color index determined by the area under the absorption curve in the region of 400–500 millimicrons is preferred over the A.O.C.S. photometric method in research on cottonseed oil color because the color index gives the more accurate measure of the relative chromogen concentration in cottonseed oils. The evidence that the color index method is more retiable includes: (a) a demonstration that the area under the absorption curve may be used in place of absorbance in the Beer‐Lambert equation; b) a panel score for cottonseed oil color intensity that agrees with the color index better than it does with the photometric color; and c) sources of error in the photometric method that do not occur in the color index method, including those contributed by the high emphasis on absorption at 550 and 670 millimicrons.

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The adsorption of fixed red pigments from refined off‐colored cottonseed oil by several adsorbents is described by the empirical Freundlich adsorption isotherm. Numerical values for the coefficient and the exponent in the Freundlich equation were determined for several oils and several adsorbeuts. Activated alumina was found to be a superior adsorbent for removing the red color bodies. It was observed that the variations from oil to oil in the numerical values of the coefficient and the exponent of the Freundlich equation were smaller for the several aluminas than they were for the other adsorbents studied. The particle size and moisture contents of the alumina, and the temperature of activated adsorption were of importance in determining the effectiveness with which the red color bodies were removed from the oils. The conditions required for optimum bleaching with alumina had no detectably adverse effect on oil quality.

1978. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.