Principal color

EEC No. E 160b), which is the monomethyl ester of the dicarboxyhc acid norhixin. The principal colorant ia alkaline aqueous extracts is norbixin [542-40-5] (36 R = H) (51,52). 

The principal coloring matter in turmeric and its oleoresin is curcumin [458-37-7] (l,6-heptadiene-3,5-dione, l,7-bis[4-hydroxy-3-methoxy-phenyl] (45), an orange-yeUow, crystalline powder, insoluble in water and ether but soluble in ethanol and glacial acetic acid. It has a reported melting point of 180-183°C. 

The large number of dyes and the potential for toxicity of dyes and dye components have made this class of compounds one of the most extensively reviewed and regulated. Up until 1987, 765 PMNs for dyes have been submitted by 53 different companies and over 50% of these notices by six companies. Figure 2 shows PMN dyes received by the USEPA, described by principal color forming group (382). 

The Wesson method, which is the principal color method for the U.S. edible oil industry, has been used for many years primarily because of its simplicity. AOCS Method Cc 13b-45 (103) determines the color of a melted fat or oil product by comparison with red and yellow Lovibond glasses of known characteristics. This method, originally developed in England for measuring the color of beer, is only intended to assess the degree of redness. Yellow is necessary for assessment of redness by allowing the colors to closely match with that of oil sample the amount of yellow was considered unimportant for this method, and a fixed yellow ratio of... 

For reference, the approximate wavelengths and complementary colors to the principal colors of the visible spectrum are given in Table 11-1. 

In a study of absorption of the compound lawsone, the principal color ingredient in henna, on human skin, two hair coloring products and two shampoo products, all containing henna, were tested on nonviable human skin. The shampoo was left on the skin for 5 min, while the coloring was left on for 1 h. For the henna hair paste products, 0.3 and 1.3% of the applied dose was absorbed into the receptor fluid in 24 hours while 2.2 and 4.0% remained in the skin. For both henna shampoo products, 0.3% of the applied dose was absorbed into the receptor fluid at 24 hours while 3.6 and 6.8% remained in the skin. For all products, most of the lawsone applied was washed from the surface of the skin (83-102%) at the end of the exposure period. Extended absorption studies were conducted for 72 hours to determine if skin levels of lawsone in the 24-hour studies might eventually be percutaneously absorbed. The studies determined that the majority of the lawsone remained in the skin with only a small increase in receptor fluid values (Kraeling et al. 2007). 

The colors observed by transmission are the principal colors. Slight changes in eolor away from the principal color are observed if the slides are tilted from the normal. This is due to the fact that interference colors shift to lower wavelengths with inereased angle of viewing. 

Table I lists some important examples of each type of yellow dye discussed above. The structures of both luteolin and quercetin, the principal coloring matters of weld and quercitron, respectively, suggest that 4,5-type chelates could form with metal ions impregnated in the fibers to be dyed. Undoubtedly, the formation of these chelates lent stability to the colors of the dyed fibers, but their importance as chelates seems to be as limited at the importance of their respective dyes.

Red wine, for example, contains porphyrins, carotenoids, anthocyanins, flavones, and tannins as the principal colorants, and the relative proportion of these determines the color and hue of the wine [1]. As the wine matures, the color gradually changes to a more browny hue as the anthocyanins link together and to other chemicals in the wine, forming polymers. Research has shown that approximately 90% of the color of some wines after maturing for a year is due to such polymers [2]. 

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