Quebracho (also known as Luciano malo) is a common name in Spanish to describe very hard (density 1.15 - 1.35) wood tree species. The etymology of the name derived from quiebrahacha, or quebrar hacha, meaning "axe-breaker".
There are at least three similar commercially important tree species that grow in the Gran Chaco region of South America.
A fourth species, Jodina rhombifolia (syn. Iodinia rhombifolia, the Quebracho flojo (the loose quebracho) or quebrachillo) of the family Santalaceae, is also sometimes mentioned.
These species provide tannin and a very hard, durable timber. Quebracho is sometimes used as a commercial name for the tannin derived from the trees or their timber.
Other species with less economical significance are also locally known as quebracho and could be found in other areas of Latin America :
as Quebracho blanco
as Quebracho colorado
as Quebracho de cerro
Quebracho produces tannins that can be extracted in quebracho sawmills from the heartwood of both red (Schinopsis lorentzii) and white quebracho (Aspidosperma quebracho-blanco). Logs are inserted into planers to produce chips that are used to produce the quebracho extract by boiling them in vats. It is used for fine leather tanning and imparts a red-brown color. Ordinary or warm soluble quebracho (also known as insoluble Quebracho) is the natural extract obtained directly from the quebracho wood. This type of extract is rich in condensed tannins of natural high molecular weight (phlobaphenes), which are not easily soluble. Its use is therefore limited to addition of small amounts during the process of tanning leather intended for shoe soles in hot liquids (temperature above 35 °C) to improve the yield and the water-proofness of the leather. The cold soluble extracts are obtained by subjecting the ordinary extract to a sulphiting process which transforms the phlobaphenes into completely soluble tannins. The cold soluble quebracho extracts are the most universally known and used types. The chemical structure of these extracts can be described as polymers of epicatechin. The main properties of these extracts are: a very rapid penetration, a high tannin content and a relatively low percentage of non-tannins. The rather low acid and medium salt content characterise them as mild tanning extracts (low astringency). Quebracho tannins give an important added value to the quality of leathers, such as vacchetta, belts and garments, making them more compact and tear resistant with a pleasant touch. The sulphited quebracho extract may be carcinogenous in mice. Other recent studies show that quebracho tannins present a strong anti-mutagenic activity. The heartwood contains from 20 to 30 percent tannin and 3 or 4 percent water-soluble nontannin. It is said to not ferment.
According to King and White (1957), the hydrolysable tannins and gallic acid found in the sapwood constitute the raw material for the biosynthesis of the condensed tannins found in the heartwood.Fustin (predominantly (-)-Fustin 66%), (-)-7:3':4'-trihydroxyflavan-3:4-diol ((-)-leuco-fisetinidin), (+)-catechin, gallic acid, fisetin and 2-benzyl-2-hydroxycoumaran-3-ones have been isolated from the heartwoods of Schinopsis balansae, Schinopsis quebrachocolorado and from commercial quebracho extract. Quebracho tannin is rich in profisetinidins and prorobinetidins. The expected masses found in mass spectrometry in negative mode in quebracho tannin are 289, 561, 833, 951, 1105, 1377, 1393, 1651 and 1667. In Quebracho colorado, the sugars and the lignins are thought to be covalently linked to the condensed tannins.
Quebracho tannin is also sold as an enological tannin. The quabracho tannins structure is very similar to that of grape tannins, making them a desirable alternative to consider comparatively because they are much less expensive to produce than grape tannins.Myo-inositol and arabitol are detected in tannins from quebracho.
The tannic acid, in the form of alkalized salts, was extensively used as a deflocculant in drilling muds in 1940s-1950s, until it was replaced with lignosulfonates. Its red color gave the mixture the name red mud.
The tanning properties of quebracho extracts were discovered in 1867 by a French tanner, Emilio Poisier, who lived in Argentina. By 1895, the quebracho extracts were exported to Europe and became the principal vegetal tannin source in the world. Amongst other activities Ernesto Tornquist (1842-1908) organised the exploitation of quebracho in Santiago del Estero, in the Chaco region. Originally a dry forest area, the abundance of quebracho attracted timber industries of British capital during the 19th century, leading to extensive deforestation. This devastated the ecosystem in a relatively short time. The private owners of the Chaco then turned to cotton production, employing the local Toba people as a cheap seasonal workforce; the conditions did not change substantially for decades.
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