Quebracho wood, tannins

The vegetable tannins can be divided into two main classes, i.e. hydrolysable and condensed. The hydrolysable tannins are obtained commercially from, for example, sumac leaves, tara pods, myrabolam fruits, Turkish or Chinese galls or oak bark. Examples of condensed tannins are those from quebracho wood, mimosa bark and gambier leaves and twigs. 

Quebracho Colorado, Red quebracho. Wood of Loxopterygium lorentzii Griseb., Anacardiaceae. Habit. Argentine Republic. Constit. Tannin, coloring matter, loxopterygine. 

Condensed tannins constitute more than 90 per cent of the total world production of commercial tannins (200000 tons per year) [11]. Their high reactivity towards aldehydes and other reagents renders them both chemically and economically more interesting for the preparation of adhesives, resins and other applications apart from leather tanning. The main commercial species, such as mimosa and quebracho, also yield excellent heavy duty leather. Condensed tannins and their flavonoid precursors are known for their wide distribution in nature and particularly for their substantial concentration in the wood and bark of various trees. These include various Acacia (wattle or mimosa bark extract), Schinopsis (quebracho wood extract), Tsuga (hemlock bark extract), Rhus (sumach extract) species, and various Pinus bark extract species, from which commercial tannin extracts are manufactured. 

Bacillus, Klebsiella, Cornybacterium, and Pseudomonas being the most frequently observed. The capacity of these bacteria to degrade tannins, and detoxify bark chips or barks extracts, was further demonstrated with pine (Pinus maritima) (51), oak (Quercus pedonculata) and gaboon wood (Aucoumea kleneana) barks (52). The degradation of quebracho and wattle tannins was also confirmed in pure cultures (53). 

Trees of the genus Schinopsis. native to the southern part of South America, including southern Brazil, Bolivia and other southern countries are very important source of tannin. These trees are known by the name quebracho, which means ax-breaker, because of their very hard, dense, heavy, dark-red wood, which is cut with difficulty. The heartwood of the tree contains 20-27% tannin, which is obtained by cutting the wood into small chips and extracting with water. Tilts tannin is often used in combination with tannins from other plants. 

For many years, most of the leather in the United States was tanned with domestic tannins from hemlock and oak bark and from chestnut wood. Today only a small amount of tannin comes from these and other domestic sources. The most important source of vegetable tannin today is the wood of the quebracho tree, which grows mainly in Paraguay and Argentina. The tannin content of this tree and a few other sources of vegetable tannin are shown in Table 28.10. 

There are a few minor wood-based chemical industries. After chestnut blight wiped out the American chestnut, U.S. tannin production essentially ceased. The main natural tannins, watde and quebracho, are now imported. High U.S. labor costs and the advent of synthetic tannins make re-establishment of a U.S. tannin industry unlikely. Tannins are used in oil-weU drilling muds. Tree exudates are a continuing wood-based chemical industry. Tree exudates include mbber, tme carbohydrate gums (eg, acacia gum), kinos (eg, the phenolic exudates from eucalyptus), balsams (eg, Storax from l iquidambar spp.), and many different types of oleoresins (mixtures of a soHd resin and a liquid essential oil). The most important oleoresin stiU collected in the United States is pine gum (rosin plus turpentine). 

Quebracho. [Climax Performance] Wood-derived tannin for leather tanning and water treatment applies.. 

Tannins from mimosa, quebracho, and pine (Pinus radiata) are actually used on an industrial scale for wood gluing. The extraction itself is only performed industrially in the southern hemisphere. The tannins are produced by water extraction of the wood or of the bark. Suitable solvents are water, alcohols [248], or acetone. Some of the parameters which influence tannin extraction are ... 

The Type 1 proanthocyanidins are distributed almost ubiquitously in the woody plants, whereas Type 2 proanthocyanidins are confined to certain families in the Leguminosae and Anacardiaceae (see Sect. 7.7.3.1), often co-existing with Type 1 proanthocyanidins either in the same or different organs of the plant. However, the Type 2 tannins are of pre-eminent importance commercially as currently the two most important sources of condensed tannins for industrial applications are wattle Acacia mearnsii) bark and quebracho Schinopsis spp.) wood, which are both of this type (Chap. 10.3). Our current knowledge of these tannins is almost entirely due to the efforts of David Roux and his colleagues over the past three decades. 

Vegetable tans, however, are based on wood, bark, leaves and roots of mimosa, quebracho, chestnut and oak. - Tannin is the active ingredient, a polyphenol (sugar derivative of gallic acid), which binds to the collagen (- proteins) by hydrogen bonds. Due to a m.w. of 500-5000, the penetration into the fibrils is slower than with chromium tans and results in heavier and fuller leathers. 

T. are extracted from various parts (wood, bark, fruits, gall apples) of trees (oak, birch, mimosa, quebracho, chestnut) with water and spray-dried. Tannin is a white to yellowish powder. 

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