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.

Application of NIR Spectroscopy for the Valorisation of Cork By-Products: A Feasibility Study over the Screening and Discrimination of Chemical Compounds of Interest

“…No pre-treatment procedures were applied. Cork powder extracts were prepared by stirring 5 g of cork powder with H 2 O or 30% EtOH, 50% EtOH, 70% EtOH, 96% EtOH, or EtOH (100 mL) at either room temperature or 40 °C, following the procedure previously reported by our team [ 4 , 6 ], using a magnetic multistirrer (Velp Scientifica, Usmate, Italy) rotating at 700 rpm. The samples were prepared as follows: Samples 1–6 were prepared by stirring cork powder for a period of 2.5 h at room temperature using H 2 O and 30%, 50%, 70%, 96% or 100% EtOH, respectively; samples 7–12 were prepared by stirring cork powder for a period of 2.5 h at 40 °C using H 2 O and 30%, 50%, 70%, 96% or 100% EtOH, respectively; samples 13–18 were prepared by stirring cork powder for a period of 1 h at room temperature using H 2 O and 30%, 50%, 70%, 96% or 100% EtOH, respectively; samples 19–24 were prepared in two extraction cycles by stirring for 1 h in each extraction cycle at room temperature using H 2 O and 30%, 50%, 70%, 96% or 100% EtOH, respectively; and samples 25–29 were prepared in two extraction cycles by stirring for 1 h in each extraction cycle at 40 °C using H 2 O and 30%, 50%, 70% or 96% EtOH, respectively.…”

“…After harvesting, cork undergoes various industrial treatments involving several production processes, depending on the intended end product. Consequently, different by-products are produced, generating a substantial amount of waste, which is a key worry inherent in this industry [ 3 , 4 ]. One of the most significant by-products is “cork powder”, comprising particles of various shapes and sizes.…”

“…In recent years, cork bark has emerged as a promising source of sustainable raw materials, capturing industrial interest in harnessing the upcycling potential of cork by-products, such as cork powder, as a rich source of bioactive compounds for various applications [ 4 , 6 , 7 ].…”

“…Aspects like geographic location, cork age (both first and second harvest), age of the tree, and the condition of the planks extracted from the trees are the primary factors influencing cork characteristics [ 8 ]. Previous studies have revealed variations in the composition and properties of the different types of cork by-products [ 4 , 6 ]. Consequently, depending on the intended application, a screening tool could be of paramount importance for appropriately selecting a suitable by-product or batch.…”

Quercus suber L. Genetic Resources: Variability and Strategies for Its Conservation

“…Cork is mostly used for wine stoppers and other products, such as agglomerates of granulates for insulation, corkboards, and cork powder [5]. Cork also has the potential to be used as activated carbon and in ecoceramics [5,6], as well as in industries where its antioxidant and aromatic properties may be useful [7,8]. While Phellodendron amurense Rupr.…”