Quercus suber Bark as a Sustainable Source of Value-Added Compounds: Experimental Studies with Cork By-Products

Abstract

Quercus suber L. bark (cork) is a sustainable material due to its ability to regenerate. The aim of this work was to explore cork powders, by-products of the cork industry, as sustainable sources of value-added compounds. Two types of cork powder were studied: coarse (P0) and fine (P1). A broad physicochemical characterization was carried out, regarding particle size, color, moisture content, hygroscopicity, pH, heavy metal content, NIR spectra, and volatile compounds. DPPH scavenging activity and total phenolic content were also evaluated for an ethanolic P1 extract. For both powders, Hg, As, Cd and Pb contents were below the acceptable limits and volatile compounds commonly used as fragrances were found in their composition. P1 had a smaller and more homogenous particle size, lighter brownish color, lower pH value, and lower moisture content than P0, and therefore appears to be more suitable for industrial application. P1 ethanolic extract also showed a high scavenging activity and a content of phenolic compounds of 50.46 ± 0.63 mg (as gallic acid equivalents) per g of extract. In conclusion, P1 cork powder seems to be a promising source of upcycled ingredients, such as fragrances and antioxidants, for the pharmaceutical, nutraceutical, and cosmetic industries.