Color quality scales

CQS Color Quality Scale HSAB Hard Soft Acid Base... 

Color quality of food can be determined by human inspectors. Although sensory evaluation is appropriate and may be the most accurate method for specifying acceptable color levels of food materials, sensory panels are not always available for routine large scale color quality determination. Moreover, their evaluations are often limited to qualitative descriptions. Human inspection is subjective, with color readings affected by the lighting conditions at die inspection site, the inspector s health and mood. 

As a consequence, other than its use in the ndM method, the refractive index is very often used in process operations because it can indicate smaii differences in product quality that would be missed by other measurements. The only restriction is that the color of the sample should be less than 5 on the ASTM D 1500 scale. 

Quality Specifications. Because of the extreme sensitivity of polyamide synthesis to impurities ia the iagredients (eg, for molecular-weight control, dye receptivity), adipic acid is one of the purest materials produced on a large scale. In addition to food-additive and polyamide specifications, other special requirements arise from the variety of other appHcations. Table 8 summarizes the more important specifications. Typical impurities iaclude monobasic acids arising from the air oxidation step ia synthesis, and lower dibasic acids and nitrogenous materials from the nitric acid oxidation step. Trace metals, water, color, and oils round out the usual specification Hsts. 

The quality of sulfonic acids produced as intermediates on an industrial scale is important to detergent manufacturers. Parameters such as color, water, free oil (unsulfonated material), and acid value (actual sulfonic acid) are all factors that determine the quality of a sulfonic acid. The quality of the feedstock prior to sulfonation, such as iodine value, water content, and sulfonatability, affects the quality of the sulfonic acid produced. Sulfonation conditions, such as temperature, molar ratio, rate, etc, also affect the quality of sulfonic acid. 

Smooth scale-ups from R D laboratory or bench scale to pilot scale and then to commercial size batch-operated, multi-purpose chemical plants are often not easy to achieve for a variety of reasons, often resulting from compromises due to the need to use existing equipment. The consequences of this lack of scalability can be a reduction in product quality and yield, increased by-product formation, longer cycle times, and, in some cases, an inability to reproduce key product properties such as color, size, or crystal structure. These consequences invariably result in an increased use of mass and energy and a production of greater waste per unit mass of product. 

Figure 4.3 To test the basic or acidic qualities of a substance, scientists use a pH indicator. The indicator is a specially treated strip that changes color when placed into the substance. The strip is then compared to a color scale that shows whether the substance is acidic, basic, or neutral in composition.

Many single number color scales have been developed for foods by converting X, Y, Z or L, a, b color specifications to a number indicating grade or quality on the desired scale. Such a scale was developed by Hunter to measure the citrus redness CR, and the citrus yellowness CY of the juice. The formulae are derived as follows ... 

Opal is a hydrous silica (Si02), sometimes thought of as an amorphous silica gel. It is a fairly soft gem, measuring only 5 to 6 on the Mohs scale. It is relatively common in nature except in its precious form, which comes mainly from Australia. In Switzerland, since 1970, opal of precious quality has been made synthetically. Usually cut in the cabochon shape to permit its rainbowlike display of color, opals come in white, black, and fire varieties. Black opals are dark gray to blue, and fire opals, which are more transparent than other opals, are usually orange-red in color. 

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