Purification of industrial tannin extract through simple solid-liquid extractions

Abstract

Acacia Mimosa or black wattle (Acacia Mearnsii) industrial tannin extracts are used as such for leather tanning, water flocculants, adhesives and many other applications. However, when higher purity of the polyphenols is requested, these extracts are not suitable anymore. Therefore, feasible strategies have to be developed in order to improve the purity of the extract. Solid-liquid extractions with common solvents were performed and the soluble and insoluble fractions of the tannin extracts in methanol and acetone were quantified and characterized through chemical analysis of phenolics, FT-IR, Py-GC/MS, LC-UV/ESI-MC and GPC. It was observed that the solvent soluble fractions were enriched of polyphenols, the insoluble residue after methanol extraction was the one presenting higher amount of hydrophobic compounds and the fraction soluble in acetone resulted purified of proteins. However, these encouraging findings suggest that this strategy does not allow to separate the phenolics from the saccharidic components which appear to be intimately interconnected.