Color development in sugars

An important consequence of sucrose degradation is the development of color from degradation products. Kuridis and Mauch60 have developed an equation for the prediction of color development in model sucrose solutions. Color development was expressed as a function of temperature (90 to 120°C), time (0 to 80 min), pH (7.5 to 9.5), and composition of the solution (sucrose 20 to 60%, invert sugar 0.02 to 0.18%, and amino acids 1 to 3 g/L). The authors claimed, with caution, that the effects of an intended alteration in a unit process in the refinery can be predicted in advance. 

Studies on the Color Development in Stored Plantation White Sugars... 

Several reactions can cause color development in starch-derived sweeteners. Because they contain reducing sugars, they will react with proteins and amino acids... 

In addition to the reactions mentioned above, there are others of this type that are used in detecting and determining specific classes of carbohydrates. The carbazole-sulfuric acid method has been much used in analysis of uronic acids and acidic polysaccharides, which give a weaker response than neutral sugars in the other methods. The presence of borate ions decreases interference by proteins and salts, increases color yield, and reduces the time required for color development. In a recommended procedure for manual analysis, the sample solution (containing 0.02-0.2 [tmol of uronic acid) is mixed (1 5, v/v) with a solution of sodium tetraborate (25mmol 1 ) in concentrated sulfuric acid and the mixture is heated at 100°C for 10 min. After rapid... 

Many of the qualitative tests may be applied to the quantitative determination of sugars. The color developed in the presence of acids and phenols or the amount of metal or metallic oxide formed by the reduction of the salts of heavy metals by the sugars can be measured. Some of these methods can also be used on a micro-scale to determine quantitatively the sugar eluted from paper chromatograms. In some cases, difficultly soluble derivations such as the osazones or hydrazones can be weighed directly. Because of the absence of a stoichiometric relation for the methods, they are not completely satisfactory. Complete descriptions of many of the methods described will be found in the article by Bell 6). 

The fruit of the native species differs markedly from the fruit of Vitis vinifera. Vinification processes in the eastern United States have developed to accommodate these characteristics. Differences are noted in sugar, acid, pectin, color, and flavor. 

Iron. Excess iron in wines causes cloudiness, interferes with the color, and can impair flavor. The mechanism of ferric phosphate precipitation has been intensively studied, and numerous colorimetric methods have been developed. For routine purposes the color developed with thiocyanate is adequate (6,9), but many enologists prefer the orthophenanthro-line procedures (3, 4, 6, 22). Meredith et al. (Ill) obtained essentially the same results for iron using 2,4,6-tripyridyl-s-triazine (TPTZ) to develop the color. Atomic absorption spectrophotometry can be used but, as with copper, corrections for reducing sugar and ethanol are necessary (51). 

The development of brown color in sugar during storage is of the oldest problems in the sugar industry. In Taiwan, about 400,000 tons of plantation white sugar from sugar cane are... 

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