Résumé
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•Douglas fir bark, a by-product of sawmills used as a source of added value products.•Isolation of polyphenols by means of dry fractionation processes.•A tannins enriched fraction was obtained from the knife milling of Douglas barks.•A taxifolin enriched fraction resulted from a knife and ball millings combination.•Taxifolin is used in cosmetic and pharmacy, tannins are used in biosourced polymers.
In order to isolate polyphenols from Douglas fir outer bark, this latter was mechanically fractionated by means of knife and ball millings. The sieving of the resulting powder gave rise to a set of fractions with different particle sizes and shapes. The particles ranging from 0.56 to 0.16mm size were mainly composed of tannins (46%) while, taxifolin was located in the coarser fraction (83%) with particles size above 1mm. The isolated phenolic compounds are suitable of upgrading to higher value products.