Color characteristics

Many cellulose derivatives form Hquid crystalline phases, both in solution (lyotropic mesophases) and in the melt (thermotropic mesophases). The first report (96) showed that aqueous solutions of 30% hydroxypropylceUulose [9004-64-2] (HPC) form lyotropic mesophases that display iridescent colors characteristic of the chiral nematic (cholesteric) state. The field has grown rapidly and has been reviewed from different perspectives (97—101). 

Blending. Most chocolate and cocoa products consist of blends of beans chosen for flavor and color characteristics. Cocoa beans may be blended before or after roasting, or nibs may be blended before grinding. In some cases finished Hquors are blended. Common, or basic beans, are usually African or BraziUan and constitute the bulk of most blends. More expensive flavor beans from Venezuela, Trinidad, Ecuador, etc are added to impart specific characteristics. The blend is deterrnined by the end use or type of product desired. 

The dyes used in the ink sheet must satisfy various requirements (/) optimum color characteristics of the three primary colors (hue, color density, shape of absorption spectmm) (2) sensitivity, ie, sublimabiHty from ink sheet to acceptor sheet (3) fastness for light and migration and (4) compatibiHty with the resin in the ink sheet. With respect to these characteristics, a large number of anthraquinone dyes have been proposed particularly for magenta and cyan colors. Typical examples are given in Table 8 and Table 9. 

In the 19-nor series, the reaction with NOF is more complex and there is isolated in addition to the fluoro nitrimine corresponding to (31) a 20% yield of the nitroso dimer (34), which dissolves in methanol-methylene dichloride solution to give the pure blue color characteristic of the monomer (35). The latter then isomerizes to the oxime (36). 

As the reaction takes place, the purple color characteristic of Mn04 fades the Fe2+ formed is pale yellow. 

The sixth coordination position of Fe2+ in heme is occupied by a water molecule that can be replaced reversibly by oxygen to give a derivative known as oxyhemoglobin, which has the bright red color characteristic of arterial blood. 

Methods are described for determining the extent to which original natural color is preserved in processing and subsequent storage of foods. Color differences may be evaluated indirectly in terms of some physical characteristic of the sample or extracted fraction thereof that is largely responsible for the color characteristics. For evaluation more directly in terms of what the observer actually sees, color differences are measured by reflectance spectrophotometry and photoelectric colorimetry and expressed as differences in psychophysical indexes such as luminous reflectance and chromaticity. The reflectance spectro-photometric method provides time-constant records in research investigation on foods, while photoelectric colorimeters and reflectometers may prove useful in industrial color applications. Psychophysical notation may be converted by standard methods to the colorimetrically more descriptive terms of Munsell hue, value, and chroma. Here color charts are useful for a direct evaluation of results. 

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. 

You can find sodium silicate in the colorful Magic Rocks seen in gift shops at museums. The dry form is mixed with salts of various metals. When you drop them in water, the sodium is replaced by the metal. The resulting metallic silicate is not soluble in water, and it takes on a color characteristic of the metal (e.g., copper is blue). The metallic silicate is also a gel, so it expands and grows into colorful stalagmites in the water. 

PRODUCT BFG.xls consists of the chemist s table, a reduced table obtained by casting out data that is not ammenable to statistical analysis such as subjective assessments ( off-white color, characteristic crystal form, pungent smell STEP 1), and the final table that was freed of all inconsistencies by going back to the original data (STEP 2). Various interesting items are highlighted ... 

The dearrangement of phenylthiourea may be demonstrated very simply by heating a small quantity of the material in a test-tube. It undergoes a violent decomposition slightly above its melting-point, the odors of ammonia, of aniline, and of phenyl mustard oil may be detected, and the residue which consists largely of sym.-diphenylthiourea gives with ferric chloride the a ed color characteristic of thiocyanic acid. 

Giusti, M.M. et al., Molar absorptivity and color characteristics of acylated and nonacylated pelargonidin-based anthocyanins, J. Agric. Food Chem., 47, 4631, 1999. 

Sinuco, D.C. et al., Application of tristimulus colorimetry to obtain natural additives from fruits. 11. Color characteristics of solids, in Proceedings of 4th International Congress on Pigments in Food, Hohenheim, Germany, Carle, R. et ah, Eds., Shaker Verlag, Aachen, 2006, 180. 

Hajjaj, H. et ah. Production and identification of N-glucosylrubropunctamine and N-glucosyhnonascorubramine from Monascus ruber and occurrence of electron donor-acceptor complexes in these pigments, Appl Environ. Microbiol, 63, 2671, 1997. Jung, H. et ah. Color characteristics of Monascus pigments derived by fermentation with various amino acids, J. Agric. Food Chem., 51, 1302, 2003. 

Antimony chloride, such as 4% SbClj in 50-ml CHCI3 or 50-ml glacial add, forms various colors characteristic of the compounds showing carbon double bonds... 

The composition and properties of the ions contained in the solution are not the same as those of ions contained in the ionic crystal lattice. It is already known that anhydrous copper sulfate (CuS04) is colorless. This implies that Cu2+ and SCT ions that make up the crystal lattice of the sulfate are colorless. When the Cu2+ ions combine with water molecules during dissolution they turn blue (the color characteristic of copper salt). This color is therefore due to hydrated ions of copper, i.e., ions connected with the water molecules. 

Pavia, M., Trujillo, A.J., Guamis, B., Capellas, M., and Ferragut, V. 1999. Changes in microstruc-tural, textural and color characteristics during ripening of Machego type cheese salted by brine vacuum impregnation. Int. Dairy J. 9, 91-98. 

Analytical Methods. The samples were analyzed by standard AACC (21) procedures for moisture (air-oven method), protein (Method 46-13), crude fat (Method 30-25), crude fiber (Method 32-10), insoluble dietary fiber (Method 32-20) and ash (600°C, 3 hr). Starch content was determined by the polarimeter method (Method 76-20) and total sugars by Method 80-60. Color characteristics of the dried products were evaluated with the Hunter Color Difference Meter. 

When oxygen was bubbled into a THF solution of 5 in the presence of methanol, the orange color characteristic of 5 disappeared immediately.54 The formation of products 52, 53, and 54 was interpreted in terms of an initial [2 + 2] cycloaddition of molecular oxygen to 5, leading to a transient dioxagermetane followed by a [2 + 2] decomposition with formation of germanone 5554 (Scheme 5). 

On standing, the filtered solids take on a color characteristic of iodine the solids can be decomposed by treatment in water with sodium thiosulfate or bisulfite to a negative starch-iodide endpoint. 

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