Total Color

A measure of the color developed by impurities when trimeUitate esters are produced can be correlated with the anhydride color measurement. The method measures the color difference in light transmittance between a trimellitic solution and a 3.0 N sodium hydroxide solution as a reference. The difference in light transmittance or AH (total color difference) is obtained using a colorimeter. 

In the process of testing, color deviations are expressed ia the CIELAB system which projects total color differences either on the axes of the rectangular LAB or the equivalent polar LHC system (26). In either case tested samples must fall within acceptable ranges or limits estabhshed versus a standard by the pigment manufacturer and accepted by the pigment user. 

In the CIELAB and CIELUV color spaces, the difference between a batch sample and a reference standard designated with a subscript s, can be designated by its components, eg, AAL = L — L. The three-dimensional total color differences are given by EucHdian geometry as the 1976 CIE lYa b and 1976 CIE lYu Y color difference formulas ... 

Lead (as Pb)—not more than 10 ppm Arsenic (as As)—not more than 3 ppm Total color—not less than 85.0%... 

Lycopene is well known as the predominant carotene in tomatoes, accounting for 65 to 98% of the total colored carotenoid content, depending on the cultivar (Table 4.2.3). The levels of lycopene in fresh tomatoes for salad varied from 21 to 79 g/g 34,35 jjj tomatoes for processing and deep-red tomatoes, the level of lycopene can be as high as 623 More than 80% of the tomatoes produced are... 

Most published data deals with model solutions to assess the major factors influencing betalain stability, among which pH and temperature are most frequently addressed. Until recently, total color loss was assessed by spectrophotometric monitoring of the decline at the wavelength of maximum absorption. To predict color fading over time, kinetic data were derived therefrom, most often obeying first-order decay principles. 

The effect of particle size, and hence dispersion, on the coloring properties of aluminum lake dyes has been studied through quantitative measurement of color in compressed formulations [47], It was found that reduction in the particle size for the input lake material resulted in an increase in color strength, and that particles of submicron size contributed greatly to the observed effects. Analysis of the formulations using the parameters of the 1931 CIE system could only lead to a qualitative estimation of the effects, but use of the 1976 CIEL m v system provided a superior evaluation of the trends. With the latter system, the effects of dispersion on hue, chroma, lightness, and total color differences were quantitatively related to human visual perception. 

In colorimetric terms, color differences are generally characterized by the distance between two colors in one of the color notation systems, most commonly the CIELAB system. The difference determined in this way represents the total color difference. Since a color is characterized by three quantities, a color difference can also be expressed in terms of three difference components (that is, differences in the color coordinates) and thus described in greater detail. Visually equal color differences between almost equal colors may, upon colorimetric measurement, be considered distinct if the colors of one pair differ strongly from those of the other pair. The formulas for color differences are further elaborated in order to remedy this defect. 

The Delta E (DE) is a single number widely used today for color acceptability. A traditional DE number is a measure of total color difference and is calculated from the individual com-... 

Under aerobic conditions Reactive Black 5 maximum total color removal was 92%. The authors attributed initial rapid loss primarily to adsorption to sludge biomass. Hydrolyzed Reactive Black 5 showed little color removal, adsorption, or degradation. Navy 106 also exhibited a loss of color over time. The initial rapid loss was likely adsorption to sludge, but the subsequent decrease may have been due either to anaerobic transformation of dyes in microanaerobic zones of the aerobic system, or to aerobic microbial degradation. 

Fig. 4.—Dependence of Color Intensity of a D-Glucose-Glycine Solution on pH. (Curve A intensity of total color curve B intensity of color due to non-melanoidin products curve C color from melanoidin formation, by difference between A and B.164)...

Table VI. Total Color Change AE (CIEL a b Color Difference Units, CDU) After Aging of Sets A and B. (4 Days...

Need unleashes creativity and resourcefulness. An appropriate and excellent example came to my attention when one of my colleagues forwarded an e-mail from Harry, a general chemistry instructor who had a totally color-blind student who could only distinguish shades of gray but with great accuracy. After some conversations, the student... 

T. Hofmann, Studies on the influence of the solvent on the contribution of single Maillard reaction products to the total color of browned pentose/alanine-solutions — a quantitative correlation by using the color activity concept, J. Agric. Food Chem., 1998, 46, 3912-3917. 

Color can be true or apparent. Apparent color is essentially total color, composed of dissolved and suspended organics and other suspended solids such as iron oxidizes. True color is measured by filtering out the suspended matter so that the only color present is due to dissolved organics. Color is measured using APHA (American Public Health Association) dimensionless units. 

Assay Not less than 85.0% total coloring matters. 

Assay Determine the total color strength as the weight percent of the sample taken using Methods I and II in Total Color under Colors, Appendix IIIC. Express the Total Color as the average of the two results. 

Identification An aqueous solution containing 2.8 mg of sample per liter exhibits absorbance intensities (A) and wavelength maxima as follows in neutral (pH = 7) and alkaline (pH = 13) solutions, A = 0.32 at 527 nm with a shoulder at 490 nm. In acid solution, a yellow-brown precipitate forms. Assay Not less than 87.0% total coloring matter. 

Method III (Sample Preparation) Proceed as directed for Method III in Total Color under Colors, Appendix IIIC. The gravimetric conversion factor (F) for Erythrosine is 1.074. Arsenic Determine as directed under Arsenic Limit Test, Appendix IIIB, using a Sample Solution prepared as directed for organic compounds. 

Other Fower Iodinated Fluoresceins Not more than 9.0%. Total Color Not less than 87.0%. 

---