Contents of tannins

A calibration graph 3-15 ppm TA concentration range was constructed and the content of tannins in sumac leaves was determined by the Folin-Ciocalteu method. 

Content of Tannins, Gossypol, and Chrysanthemln In Cotton Plant Tissues Seasonal Averages for 3 August 1981 Replicates,... 

To obtain the prescribed concentration, a preliminary test must be made if there is no indication of the approximate content of tannin in the substance. In general this concentration is obtained approximately by weighing out, for each litre of solution, the following quantities of the different tanning materials (see Joum. Soc. Chem. Indus-... 

Plant material is well known for its contents of tannins and various phenolic compounds that may polymerize-precipitate on the surface. It is... 

Pyrolysis techniques were applied for the evaluation of catechol content of tannins from different plant materials [1,2], or for the quantitation of tannin content in products such as wine [2]. 

Analyses of yumberry juice show a cross section of essential nutrients, but levels are not as high as in the top superfruits. More than a hundred reports on bayberry are in the medical research database, most of these identifying polyphenols extracted from the tree bark or leaves. Ellagic acid is the dominant polyphenol in yumberry juice among many isolated polyphenols, including high contents of tannins and anthocyanins. 

In order to avoid side-effects, the daily administration shonld not exceed 2 weeks and should involve the nse of cold water to prepare an infusion with a low content of tannin. 

COWBERRY (Cranberry), Vitis idaeaefolium, from Vaccinium vitis idaea L. The leaves have the advantage of having a lower content of tannins. The arbutin content is about 5%. 

Table 6. (A) Contents of tannins in the extracts of Geranii Herba...

Wanasundara and Shahidi (1994a) reported that the total content of phenolic acids of flaxseed meal was about 220 mg/lOOg, on a dry weight basis. Methanol-ammonia-water/hexane extraction lowered the total phenolic acid content of the meals by approximately 48%. The content of condensed tannins of flaxseed meal was about 136 mg/lOOg, determined as (+)catechin equivalents, and this must have originated from the seed coat. The two-phase solvent extraction system (methanol-ammonia-water/hexane) reduced the content of tannins in the meal by 74% (Wanasundara and Shahidi, 1994a). 

Investigations have focused on the content of polyphenoHcs, tannins, and related compounds in various foods and the influence on nutrient availabiHty and protein digestibiHty. It has been estabHshed that naturally occurring concentrations of polyphenoloxidase and polyphenols in products such as mushrooms can result in reduced iron bio availabiHty (75). Likewise, several studies have focused on decreased protein digestibiHty caused by the tannins of common beans and rapeseed (canola) (76—78). 

Tannins are polyhydroxyphenols. They are soluble in water, aleohols and aeetone and ean eoagulate proteins. They are yielded by extraetion from wood substanee, bark, leaves and fruits. Other components of the extraction solutions are sugars, pectins and other polymeric carbohydrates, amino acids and other substances. The content of non-tannins can reduce wood failure and water resistance of glued bonds. The polymeric carbohydrates especially increase the viscosity of the extracts. 

The most widely used method is based on the reaction between potassium iodate and hydrolyzable tannins (Hartzfeld and others 2002). This method provides a good estimate for gallotannins but underestimates the content of ellagitannins. 

Proanthocyanidins (PAs), also known as condensed tannins, are oligomeric and polymeric flavan-3-ols. Procyanidins are the main PAs in foods however, prodelphinidins and propelargonidins have also been identified (Gu and others 2004). The main food sources of total PAs are cinnamon, 8084 mg/100 g FW, and sorghum, 3937 mg/100 g FW. Other important sources of PAs are beans, red wine, nuts, and chocolate, their content ranging between 180 and 300 mg/100 g FW. In fruits, berries and plums are the major sources, with 213.6 and 199.9 mg/100 g FW, respectively. Apples and grapes are intermediate sources of PAs (60 to 90 mg/100 g FW), and the content of PAs in other fruits is less than 40 mg/100 g FW. In the majority of vegetables PAs are not detected, but they can be found in small concentrations in Indian squash (14.8 mg/ 100 g FW) (Gu and others, 2004 US Department of Agriculture, 2004). 

Adsorption measurements were made by batch technique at room temperature (25 3°C). Known amounts of tannin resin were placed in 250 mL erlenmeyer flasks containing 100 mL of metal ion solution of known concentration and were stirred for a given time period. The solutions were then filtered, centrifuged and the concentrations of metal ions were measured by AAS. The difference in the metal ion (Pb + and Ztf+) content before and after adsorption represented the amount of Pb and Zn adsorbed by new resin. 

Rhus coriaria L. is a shrab, which reaches 3M p in high in the wild. Its powdered leaves were used as a tanning agent for its high tannin content [10]. Tannins are found in the leaves, fmit, barks, roots and wood of trees. They can be classified into two groups condensed tannins and hydroly sable tannins [11]. The co-occurrence of both kinds of tannins in the same plant or plant tissue is often observed [12]. The main compounds present mRhus coriaria L. are hydrolysable gallatonnins. 

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