Study on the Valorization of Oak Bark Biomass - Part I: Extraction and Characterization of Tannins

Oak bark, an abundant but underutilized biomass, is often combusted as fuel or discarded.This study aims to valorize this biomass by efficiently extracting tannins, a class of natural polyphenolic compounds.The effects of bark particle size, solvent type, and solvent concentration on the extraction yield and tannin composition were evaluated.The highest extraction yield (6.3%) was obtained from bark particles with a size range of 20-40 mesh.Despite their slightly lower extraction yields, finer particles (> 40 mesh) exhibited higher total polyphenol and tannin contents.Among the solvents tested, 90% ethanol provided the highest average yield (6.4 %), whereas acetone resulted in lower yields but higher tannin purity.The recovery efficiency of condensed tannins was maximized when bark particles > 40 mesh were extracted using 90% ethanol.These findings demonstrate the crucial roles of particle size and solvent selection in determining the quantitative and qualitative efficiency of tannin extraction, confirming the potential of oak bark as a valuable biobased resource.