CHEMICAL COMPOUNDS astringents

The natural moisture of the cocoa bean combined with the heat of roasting cause many chemical reactions other than flavor changes. Some of these reactions remove unpleasant volatile acids and astringent compounds, partially break down sugars, modify tannins and other nonvolatile compounds with a reduction in bitterness, and convert proteins to amino acids that react with sugars to form flavor compounds, particularly pyrazines (4). To date, over 300 different compounds, many of them formed during roasting, have been identified in the chocolate flavor (5). 

C.-T. Ho S. Sang J. W. Jhoo, Chemistry of Theaflavins The Astringent Taste Compounds of Black Tea. In Challenges in Taste Chemistry and Biology, T. Hofmann, C.-T. Ho, W. Pickenhagen, Eds. ACS Symposium Series 867 American Chemical Society Washington, DC, USA, 2004 pp 125-138. 

The high abundance of aluminum has resulted in a multitude of apphcations for the element and its compounds. Aluminum derives its name from alum, the double sulfate KA1(S04)2-12H20, which was used medicinally as an astringent in ancient Greece and Rome. Today, aluminum plays an important role as the pure metal and its alloys while its compounds have extensive applications as structural and medical ceramics, electronic and optical materials, catalysts, ionic conductors, coagulants for water purification, and reagents for preparation of other chemicals. " ... 

Astringency is a tactile sensation, which is often described as a puckering, rough or drying mouthfeel. The mechanism of its perception is unknown, although it is probably mediated by touch or mechanoreceptors 4). Chemically, astringents have been defined as compounds which precipitate proteins. For water soluble phenols, this has been reported to require molecular weights between 500 and 3000 daltons (5). 

Tannins are a broad class of complex phenolic compounds that are comprised of two chemical groups the hydrolyzable tannins (gallotannins) and the condensed tannins (proanthocyanidins). Tannins bind to and precipitate proteins, producing the astringent activity of tannin-containing herbs. Tannins are natural components of many herbs and common foods, and some tannins are used in the processing of foods, alcoholic beverages, and medicines. 

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