Visual color

The most used EIA reagents conjugate a fluotophote such as fluorescein-isothiocyanate (EITC) or thodarnine—isothiocyanate to antibody (or antigen) free amino groups. Examples of other commonly used fluotophotes for EIA and their spectral characteristics ate presented in Table 3. EIA assays ate available in sandwich and competitive formats similar to EIAs. Unlike EIA kits which can be used directly with visual color deterrnination, EIAs require a fluorometer, and thus ate primarily laboratory-based. [Pg.26]

Color. The visual color, from white to dark brown, of sugar and sugar products is used as a general indication of quaUty and degree of refinement. Standard methods are described for the spectrophotometric deterrnination of sugar color that specify solution concentration, pH, filtration procedure, and wavelength of deterrnination. Color or visual appearance may also be assessed by reflectance measurements. [Pg.11]

Color. Color is deterrnined through the use of a Nessler-type visual color comparator as described in ASTM Designation D1209. [Pg.35]

Color-order systems, such as the many MunseU collections available from Macbeth, have been described previously. Essential for visual color matching is a color-matching booth. A typical one, such as the Macbeth Spectrahte, may have available a filtered 7500 K incandescent source equivalent to north-sky daylight, 2300 K incandescent illumination as horizon sunlight, a cool-white fluorescent lamp at 4150 K, and an ultraviolet lamp. By using the various illuminants, singly or in combination, the effects of metamerism and fluorescence can readily be demonstrated and measured. Every user should be checked for color vision deficiencies. [Pg.417]

The objective indication of color differences in foods has usually been attempted in a simplified, indirect way that involves a comparison of some physical characteristic of the samples or, more often, an extracted fraction that is assumed or has been proved to be largely responsible for the associated color characteristics. Although such a method does not measure the actual visual color of the samples, a measure of relative amounts of color-characteristic pigments or a comparison of physical properties of extracts of color-critical fractions (which may be mixtures of several pigments) may prove to be very sensitive indications of differences that are closely related to color. [Pg.4]

The indirect methods discussed thus far have dealt with measurement of color only as it can be correlated with physical characteristics of materials and the effect of these materials on radiant energy. As has been pointed out, the reflectance spectro-photometric curve describes a property of the material. A change in the reflectance spectrophotometric properties may not always result in a change in visual color. The reason is that color of the object is not an unchangeable characteristic of the object itself, dependent only upon these reflectance properties, but is also dependent upon the quality of the illuminating light and the sensitivity of the observer s eye. Thus the measurement and description of visual color are psychophysical problems... [Pg.6]

Food colorants are analyzed either by direct inspection (sensorial analyses) or by physical or physicochemical instrumental methods. Direct inspections determine the sensorial attribute of color, frequently combined with assessments of smells and flavors. Visual color assessment is subjective and may be used with reliable visual evaluations controlling multiple variables. [Pg.522]

First, a food quahty relationship model has been developed. It considers food quahty (FQ) to be dependent on food behavior (FB) and human behavior (HB). FB is a function of food dynamics (FD) (such as variable pigment concentrations and differing color degradahon prohles) and apphed technological conditions (TCs) (such as oxygen control to maintain color concentrahons). Likewise, HB is a function of human dynamics (HD) (for example, varying color perceptions due to age differences), and administrative conditions (ACs) (such as use of color cards to support visual color inspection). These relations are reflected in the food quahty relationship model as ... [Pg.554]

The degradation kinetics of total carotenoid contents and visual color of papaya puree were investigated at temperatures between 70°C and 105°C (Ahmed et al. 2002). The thermal degradation of total carotenoids and color change parameters (Hunter, axb values) followed first-order reaction... [Pg.235]

Ahmed, J., U. S. Shivhare, and K. S. Sandhu. 2002. Thermal degradation kinetics of carotenoids and visual color of papaya puree. J. Food Sci. 67 2692-2695. [Pg.250]

The fluorescent properties of NHS-fluorescein are similar to FITC. The wavelength of maximal absorbance or excitation for the reagent is 491nm and its emission maximum is 518nm, exhibiting a visual color of green (Sheehan and Hrapchak, 1980). Its molar extinction coefficient at 491 nm in a pH 8.0 buffer environment is Other components in... [Pg.404]

Neaalertubea analychem Standardized glass tubes for filling with standard solution colors for visual color comparison with similar tubes filled with solution samples. nes-lar, tubz ... [Pg.258]

Figure 8.7 Schematic representation of the recombinations of polymer 29 and 30 to obtain visual color changes (a) in solution and (b) in neat [26].

Figure 25 Calculated saturation effect for a 1 1 mixture of Py and Ox. This effect changes the visual color of the material.

Color, as used here, has nothing to do with visual color. The manner in which different colored quarks combine in quantum mechanics is suggestive of the way in which visual colors combine. Hadrons are "colorless 7 since they are averages of the three colors. [Pg.1397]

A written method would define the viewing conditions. They must be the same for all observers when judging color. An excellent reference for guidance in visual color appraisal is the published standard ASTM D 1729-96 (ASTM, 2000). [Pg.973]

Metal complexes are used for compound identification. They can shift or change absorption spectra, change the Rf of compounds in thin layer chromatography, and change visual colors used in chromatography. [Pg.45]

He also developed the Hunter L, a, b scale. This scale is easier to identify with visual color than the X, Y, Z scale. [Pg.307]

Huggart (17) using a Hunter Citrus Colorimeter developed an equation containing CR and CY values which established a high correlation between instrument color values and U. S. Department of Agriculture visual color scores. The State of Florida... [Pg.307]

As pink or red—fleshed grapefruit ripen, the color of the juice loses the distinct coloration and gives a juice that is definitely amber with a very slight brownish cast. Mixtures of white-fleshed and pink-fleshed grapefruit have a dull appearance and may look grayish to dull amber. There are no visual color standards for grapefruit juice products. However, color characteristics may be measured on tristimulus colorimeters using the L, a, b, color notation. [Pg.310]

Figure 7. Interactions of Nation s side chains and a Pt nanoparticle. A light brown color indicates Pt atoms at distances closer than 6.79A° from an S atom. Atoms that are in regions around the sulfonic groups have been enlarged to improve visualization. Color codes are white and red for H and O in water, respectively, green for F, gray for C, and yellow for S 73 Reprinted from Electrochim Acta, Vol. 50, Balbuena et al., Molecular modeling studies of polymer electrolytes for power sources, p. 3788, Copyright (2005), with permission from Elsevier.

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