Colorants brown polyphenols

Francis, F.J., Caramel, brown polyphenols and iridoids, in Colorants, Eagan Press, St. Paul, MN, 83,1999. 

There are two important sources of brown polyphenols, cocoa and tea, used as colorants for foods. Both are very old and date back to antiquity. 

FRANCIS, F. J. Caramel, Brown Polyphenols, and Iridoids. Chap. 10 in Colorants, Eagen Press, St. Paul, MN, 1999, pp. 83-8. 

PVPP is commonly used to remove undesirable brown or pink pigments from wine (Jackson, 1994). However, because much of the color of red wine is due to polyphenolic compounds, treatment with PVPP or other polyamides can diminish the red color and so must be carefully controlled. Additions of gelatin or egg white (egg albumin has about... 

Aqueous tea extracts deteriorate rapidly during storage. They develop an undeslreable taste commonly described as "flat" and concurrently turn dark brown in color. Roberts et al. (56) used a modification of the HPLC procedure of Hoefler and Coggon T57) to separate the polyphenols in tea to study this problem. The effluent from the reverse phase acetone gradient was monitored at 380 nm. 

Among polyphenolic compounds, two types of flavonoids, the anthocyanins and flavanols (i.e., catechins, proanthocyanidins, condensed tannins), are particularly relevant to the quality of red wines, as they are key compounds for color definition and astringency. Other flavonoids such as flavonols may have some influence on color and bitterness, although they are present in red wines in much lower amounts. Phenolic acids and hydrolysable tannins, released from barrel wood, may also have an influence on wine taste and color, and hydroxycinnamoyl derivatives from grape must are involved in the oxidative browning of white wines together with flavanols. Besides, some of these perceptions may be modified by other sensory characteristics (e.g. sourness, sweetness) related to other wine components (Preys et al. 2006). 

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