how are tannins removed using sodium carbonate

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What is condensed tannin?

Condensed tannins from wood and bark are flavonoids oligomers and copolymers. The tannin extraction looks like lignin extraction (pulping): a polyphenol is separated from a polysaccharide matrix. The extraction is facilitated with inorganic and or organic reagents. Commercial tannins are mainly extracted from Mimosa bark and Quebracho wood. Tannin extraction from pine bark has been of a great interest for industry. Analysis of condensed tannins is complicated by the presence of other chemical compounds resulting from the extraction process. Colorimetric and titration methods are used to determine tannin purity or content in a sample. Tannin oligomers can be fractionated with high-perfomance liquid chromatography and gel permeation chromatography. The exact molecular structure of tannins is mainly investigated by using nuclear magnetic resonance spectroscopy and mass spectrometry. This chapter presents a compressive overview on wood tannin extraction, commercial production, and related analytical methods to characterize this polyphenolic.

Where are tannins found?

... According to [2], tannins are the most important substances in plants, found in the wood, bark, fruit leaves, and roots, which occur naturally. and is used as a leather tanning material [3]. ...

What is the carbon in a tree?

A tree stores carbon and energy. The stored carbon is part of very complex chemical structures. The major wood components that have macromolecular structure are cellulose, lignin, and hemicellulose. The carbon content is high, and the oxygen content is high as well. Many different covalent bonds—with a broad diversity of bond dissociation energies—exist in those macromolecular structures. There are interactions and covalent bonds between different wood components. The challenge of the modern biorefinery is to manage the available chemical compounds with minimum damage to their structure. To achieve a profitable biorefinery, all the components should be considered equally important during the tree fractionation. Profitability strategies including preserving the chemicals’ structures and delaying the conversion of carbon back to carbon dioxide must be considered. The biorefinery should be a buffer between the high wood quality variability and the lower variability of the target lignin and tannin products.