Tannin INDEX

Boiler Pressure Tannin Reserve Tannin Index/... 

When testing for a tannin reserve or tannin index, the presence of natural color aids detection. Testing for tannin is simple and relatively accurate using either a permanganate reduction test (development of permanent purple color) or lignin/tannic acid polymer test (tungstate blue color). 

However, the usual tests for characterizing active carbon — such as the phenol number, the surface area (BET 2)> tl tannin index or the iodine index — are inadequate for evaluating the potential removal of the humic substances by the carbon. Moreover the resulting adsorption may differ according to the source and previous treatment of those substances and the characteristics of the feed water used. 

Cannas, A., 1999 TANNINS Fascinating but Sometimes Dangerous Molecules , http //www.ansci.comell.edu/plants/toxicagents/tannin/index.html. 

Hplc techniques are used to routinely separate and quantify less volatile compounds. The hplc columns used to affect this separation are selected based on the constituents of interest. They are typically reverse phase or anion exchange in nature. The constituents routinely assayed in this type of analysis are those high in molecular weight or low in volatility. Specific compounds of interest include wood sugars, vanillin, and tannin complexes. The most common types of hplc detectors employed in the analysis of distilled spirits are the refractive index detector and the ultraviolet detector. Additionally, the recent introduction of the photodiode array detector is making a significant impact in the analysis of distilled spirits. 

Concerning the properites of tannins, we have stressed the importance of their structure, even more than their state of condensation or molecular weight. As it is impossible to separate and identify the flavolans in a given plant sample, one must be content with finding the aggregate indexes expressing the median state of polymerization. 

Length of skin-juice contact, days Tint Color Intensity Antho- cyanins, gram,/ liter Tannins grams/ liter V/LA Perman- ganate Index... 

Conditions Color Tint Intensity Antho- cyanins, mg/liter Total Phenols Index Tannins, grams/ liter Tannin Conden- sation Index, V/LA... 

Geranium maculatum s 10-18 percent tannin content would make it a useful astringent. See The Merck Index, p. 4412. 

Contains spigeline, resins, tannin, and volatile oils. Still listed as an anthelmintics in The Merck Index, p. 8900 and PDR for Herbal Medicines, p. 1155. jSeveral studies support its use in this regard. See Mowrey, Vaiidation ofHerbai Medicine, p. 240 and PDR forHerbai Medicines, pp. 672-673. 

The carbons produced were tested for iodine number (AWWA B 604-74), methylene blue index (Norit procedure), phenol value (DIN 19603), tannin value (AWWA B 600-78), and BET-surface (VUB). 

Other studies have described similar results to those found in our research, that is, that ellagitannins are more abundant in French oak (26) and therefore, in wines matured in French oak barrels. So, the presence of ellagitannins enhances the color of wine and increases absorbance at 620 nm by fevoring anthocyanin-procyanidin type tannin condensations with acetaldehyde (purple pigments) and that foct also helps to explain the higher PVPP index values of wines fix)m new French oak barrels. They also prevent the development of brick-yellow color by preventing the oxidation of phenolic compounds (24). 

The HCl index, therefore, reflects the state of polymerization of tannins in the wine, which, in turn, depends on the aging conditions. For example, polymerization decreases after winter... 

The procedure consists of adding 5 ml of cold-soluble gelatin solntion (70 g/1) to 50 ml of red wine. After three days, the wine is centrifuged and the tannins (LA) in the supernatant diluted to 1/50 are assayed to determine the tannin concentration Cl (g/1). Co is the tannin concentration of the control, prior to the addition of gelatin. The gelatin index is given by the equation ... 

Making objective measurements of these basic sensations is particularly complex. However, the gelatin index provides an estimate of reactivity to proteins. The intensity of the polyphenol-gelatin reaction depends on conditions in the medium. Acidity is a favorable factor, unlike alcohol content, which inhibits the reaction and gives a sweet taste. The reaction is independent of the tannin concentration at values above 50 mg/1 (Glories, 1983). Under given reaction conditions, it is thus possible to classify the various polyphenols according to their aptitude to combine. 

Table 6.10. Effect of terroir (soil and microclimate) on the reactivity to proteins of tannins in wine gelatin index and tannic strength (TS) (Merlot from Saint-Emilion, 1992 vintage) (de Freitas, 1995)...

Vineyard Tannins (g/1) Gelatin index Tannic strength (NTU) Tasting notes... 

Tannins in the stalks are polymerized, non-colloidal procyanidins (HCl index = 35-40) with a reactivity similar to that of tannins in seeds. 

OD 280 Tannins (g/1) Anthocyanins (mg/1) Polysaccharides (mg/1) Dialysis index Gelatin index... 

Wines Appellations Total phenols (index) Tannins (g/1) d(meq/l)... 

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