Coloring matter development

Important twentieth-century developments include the addition of Molybdate Red to the series of inorganic synthetic coloring matters in 1936 Titan Yellow followed in 1960. 

Changes in coloring matter the (mauve) complexes with ethyl cross-bonds develop into orange pyrano-vinyl procyanidins. The reaction kinetics are disturbed by the presence of polysaccharides and, are apparently temperature dependent. This explains the difference between great wines that remain truly red for many years and more modest wines that rapidly take on a more yellow hue, as well as those that are saturated with oxygen during the winemaking process. 

The above transformations result in a reduced anthocyanin content, contrasting with the increase in color. The new condensed pigments formed are more intensely colored than anthocyanins. Other anthocyanin and tannin breakdown reactions may lead to a loss of color, generally accompanied by a tendency towards yellow-orange hues. This is characteristic of the normal development of bottle-aged red wines. The breakdown of anthocyanins involves a loss of molecular structure in the red coloring matter, possibly accompanied by the appearance of a yellowish hue. 

Influence of External Conditions on the Development of Coloring Matter and Tannins... 

It is apparent from the preceding considerations that two physicochemical factors, oxidation and temperature, have a particularly strong influence on the various reactions responsible for the development of coloring matter and tannins. The following paragraphs summarize all the phenomena involved ... 

Low temperatures, on the contrary, do not cause any particular problems, but rather facilitate the precipitation of colloidal coloring matter. Oxygen dissolves more easily, leading to oxidation of the medium, and various reactions take place more slowly. However, it is not advisable to keep wine at low temperatures for too long, as development is inhibited and there is a significant risk of oxidation, but a few weeks exposure to cold is strongly recommended. 

Detection of Sophistication. In Europe where red wines of full color are desired, and the lack of maturity tends to prevent full color development, addition of foreign coloring matter is occasionally practiced. Various methods have been devised for the detection of such additions. 

When hexuronic acids are boiled with strong acids and naphthoresorcinol, a blue color is formed. This reaction has been developed into a quantitative method (69). The coloring matter formed is extracted with benzene and determined photometrically. (See also Chapter XII, for identification and analysis.)... 

The method developed by Epton [212,213] became the universally accepted method for the analysis of active matter of anionic and cationic surfactants. Epton s method, also known as the two-phase titration, is based on the titration of the anionic surfactant with cetylpyridinium bromide, a cationic surfactant, in the presence of methylene blue as indicator. A solution of the anionic surfactant is mixed with the indicator dissolved in dilute sulfuric acid, followed by further addition of chloroform, and then it is titrated with the cationic surfactant. Methylene blue forms a complex with the anionic salt that is soluble in chloroform, giving the layer a blue color. As the titration proceeds there is a slow transference of color to the water layer until the equivalence point. At the equivalence point colors of the chloroform and water layers are visually the same. On successive additions of titrant the chloroform layer lightens in shade and finally becomes colorless. 

Illuvial accumulation of organic matter Residual accumulation of sesquioxides Illuvial accumulation of sesquioxides Accumulation of clay Development of color or structure... 

As a matter of course, replacement of (cyclo)alkylamino groups with arylamino groups will result in a bathochromic shift. For example, 3 -anilino-6 -chlorofluoran (23)13 develops yellowish red color. 

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