Astringent General

Astringents are designed to dry the skin, denature skin proteins, and tighten or reduce the size of pore openings on the skin surface. These products can have antimicrobial effects and are frequendy buffered to lower the pH of skin. They are perfumed, hydro-alcohoHc solutions of weak acids, such as tannic acid or potassium alum, and various plant extracts, such as bitch leaf extract. The alcohol is not only a suitable solvent but also helps remove excess sebum and soil from the skin. After-shave lotions generally function as astringents. 

Tea oxidation is generally referred to as fermentation because of the erroneous early conception of black tea production as a microbial process.66 Not until 1901 was there recognition of the process as one dependent on an enzymically catalyzed oxidation.67 This step and further reactions result in the conversion of the colorless flavanols to a complex mixture of orange-yellow to red-brown substances and an increase in the amount and variety of volatile compounds. Extract of oxidized leaf is amber-colored and less astringent than the light yellow-green extract of fresh leaf and the flavor profile is considerably more complex. 

Data for the metabolites in plasma are generally for the unbound forms, but there is ample evidence that PPT bind noncovalently to proteins. Most studies on PPT-protein interaction have focused on protein utilization or astringency but a few studies have addressed binding to plasma proteins and lipoproteins. " " Strongest binding has been associated with 1,2-dihydroxyphenols and proline-rich proteins such as those character-istic of human saliva and structure-activity relationships have been reported. 

The widely used preparations are gum acacia and tragacanth. vi. Tannins are nonnitrogenous constituents of plant. Chemically they are phenolic derivatives and are characterized by their astringent action. Tannins are generally employed in the treatment of diarrhoea and burns. The important plants which contains tannins are Amla, Behera, Hirda (in combination form Triphala ), Black catechu and Ashoka bark. 

In dentistry, when astringents and antiseptics are used to harden and dry tissues of the pulp and root canal so that the tissues are resistant to infection, they are termed as mummifying agents. It is used in certain dental procedures when it is not possible to completely remove the pulp and contents of root canal. For this, generally a combination of various mummifying agents are used in the form of paste or semi-liquid preparation like tannic acid glycerine. 

As a bitter tonic without astringency, in weakness of stomach function and indigestion generally. The infusion of 1 ounce of the powdered root to 1 pint of cold water is taken in two tablespoonful doses three or four times daily. 

The manipulation of the cap, the length of time the juice is kept in contact with the skins, and the temperature of fermentation are three important variables available to the enologist to produce a wine of the depth of color and flavor, degree of astringency and bitterness, and general texture and longevity that he wishes his wine to have. Later in the process there are additional variables but none is more important than these three. 

After free draining, the pomace is removed and pressed. The press wine, which yields 30-45 gallons per ton, is dark red, high in tannin, and heavy bodied. This press wine generally is segregated from the free-run fraction and, after separate clarification to reduce the astringency caused by polyphenolic compounds, may be blended in with the main free-run volume. 

Grape phenolics compounds are important to wine colour, flavour, astringency and bitterness, with red wines generally containing 1200-1800 mg gallic acid equiv-alents/L of total phenolics, six- to ninefold more than present in white wines (Kennedy et al. 2006). Hydroxycinnamic acids (non-flavonoid phenolics) are major phenolic compounds of white wines and are responsible for their colour. Other non-flavonoid phenolics contribute flavour, such as vanillin, vinyl phenols and gallic acid. Vinyl and ethyl phenols, which can be present to variable extents, elicit phenolics, medical, Bandaid , barnyard and spicy characters in wine, which are generally... 

It is usual amongst experienced tasters to employ general and subjective terms to define astringency or sub-qualities of astringency. To categorize the vocabulary. 

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