Pigments formation

Fujikawa, S. et ah. Brilliant skyblue pigment formation from Gardenia fruits, J. 

Coupled with the latter investigations, it was shown that a diazo suspension can be fed through a micro device without leading to plugging [55]. This broadens the scope of micro processing applicability towards azo pigment formation. 

Sullivan, D. J. Theories on malarial pigment formation and quinoline action. Int. J. Parasitol. 2002, 32,1645-1653. 

Another family of technically important diazo components for pigment formation includes a series of aromatic diamino compounds, primarily 3,3 -dichlorobenzidine, and to a lesser extent 3,3 -dimethoxybenzidine (o-dianisidine), 3,3 -dimethylbenzidine (tolidine) and 2,2, 5,5 -tetrachlorobenzidine ... 

The overall process can be related to two operations diazotization and coupling. Out of the vast number of patents concerning continuous methods of azo pigment formation, the following examples have been chosen. 

In the past it used to be quite common for customers of the pigment industry, especially for printing ink manufacturers throughout western Europe, to be supplied with the sodium salts of the sulfonated (3-naphthol compounds. Pigment formation, e.g., precipitation was then typically carried out by the printing ink manufacturer. 

DMAC does not detect urea, but uronium ion (8). Another color test for urea nitrate, which is less specific but is simple and quick, was developed in Israel by A. Bomstein. It is based on the fact that urea nitrate is highly acidic thus, the pH indicator bromophenol blue changes its color from blue to yellow upon reaction with trace amounts of urea nitrate [95]. Red pigment formation in the reaction between p-DMAC and urea nitrate [91, 92] is as follows ... 

Enough heat is generated by the reaction to keep the suspension at boiling point. It is essential to have an excess of iron metal to ensure complete decomposition of the nitrobenzene. The details of the reaction mechanism are not fully understood, but it is presumed that the nitrobenzene oxidizes Ee to Ee which is then hydrolysed. The acid is released by hydrolysis and pigment formation and dissolves the metallic iron and thus renews the supply of Ee " no additional acid other than that produced dur-... 

O2 oxidoreductase (E.C. 1.10.3.1.) and peroxidase (E.C. 1.11.1.7.) contribute to secondary pigment formation during curing processes (J ) and during stresses to plants caused by ozone ( > ) diseases, chemicals, physical wounding and adverse temperatures, moisture and nutrient levels (, ). The resulting pigments contribute to abnormal foliar and food coloration (6) and flavors (, 7) of plants and plant products. 

The berry or the small fruits consist of strawberry, raspberry, blackberry, black currant, blueberry, cranberry and elderberry. The volatiles responsible for the flavour of small fruits are esters, alcohols, ketones, aldehydes, terpenoids, furanones and sulfur compounds (Table 7.3, Figs. 7.1-7.7). As fruit ripen, the concentration of aroma volatiles rapidly increases, closely following pigment formation [43]. 

The type and quality of the pigment are determined not only by the nature and concentration of the additives, but also by the reaction rate. The rate depends on the grades of iron used, their particle size, the rates of addition of the iron and nitrobenzene (or another nitro compound), and the pH value. No bases are required to precipitate the iron compounds. Only ca. 3 % of the theoretical amount of acid is required to dissolve all of the iron. The aromatic nitro compound oxidizes the Fe2 + to Fe3 + ions, acid is liberated during hydrolysis and pigment formation, and more metallic iron is dissolved by the liberated acid to form iron(II) salts consequently, no additional acid is necessary. 

Pigment Formation Heme status Heme iron state Globin status Color... 

The pigment formation in the case under consideration here is then organized in 5 steps ... 

This is, however, not so in extreme cases, since, as shown above, the velocity of reaction is very strongly negatively influenced by the massively decreased water content at higher temperatures (see above) decreased mobility of the reaction partner, decreased reactivity of iron, increased evaporation of ad-/absorbed hydrogen cyanide etc. (see chapters 6.5.2. and 6.5.3.). A strong reduction in pigment formation must therefore be expected at increased temperatures. 

Early work by Hannan and Lea187 on pigment formation was concerned with glucose in relation to casein, poly-L-lysine, and V -acetyl-L-lysine. Similarity in behaviour fitted the expectation that the group primarily involved is the e-amino group of protein-bound lysine. Chemical tests suggest that colourless IV-glycosides are formed first, followed by Amadori compounds. 

The kinetic expression for the Chi formation was made according to a pigment formation model proposed in the previous paper [42]. In this model, it was postulated that the pigment was accumulated in an organelle by means of per-... 

Another important observation concerning growth characteristics of plant cells deals with the separation of growth and production phases, especially for a large number of secondary metabolities. Certain media components will favor growth while other components will favor secondary metabolite production. This has been extensively documented with pigment formation by Lithospermum erythrorhizon (33) and the phenolics production in Nicotiana tabacum (34). 

Methyl groups at positions 5, 9 and 13 on retinal are not a necessity for pigment formation. This was shown by synthesis and formation of visual pigment analogs from 5-desmethyl, 17 [145], 9-desmethyl, 18 [70,176-180], 13-desmethyl, 19 [176-180] and 9,13-desmethylretinal, 20 [70,176,177],... 

Birbeck, M. S. C. and Barnicot, N. A., Electron microscope studies on pigment formation in human hair follicles, in Pigment Cell Biology, Gordon, M., Ed., Academic Press, New York, 1959, 549. Thody A. J., Higgins, E. M., Wakamatsu, K., Ita, S., Burchill, S. A., and Marks, J. M., Pheomelanin as well as eumelanin is present in human epidermis, J. Invest. Dermatol., 97, 340,1991. 

Revilla, I., Gonzalez-San Jose, M.L. (2001). Evolution during the storage of red wines treated with pectolytic enzymes New anthocyanin pigment formation. J. Wine Res. 12, 183-197. 

---