Valorization of Pinus taeda bark: source of phenolic compounds, tannins and fuel : Characterization, extraction conditions and kinetic modelling
2021
Xavier, Lúcia | Barrenengoa, Manuel | Dieste, Andrés | Amilivia, Agostina | Palombo, Viviana | Sabag, Marcel | Zecchi, Berta
Pine bark is a byproduct of wood processing which is usually burnt for energy. This article analyzes the liquid–solid extraction of Pinus taeda bark to obtain phenolic compounds by using response surface methodology to determine extraction conditions. The independent variables studied were temperature, ethanol concentration and solid–liquid ratio, and the variables to be optimized were total extractives yield, phenolic content, antioxidant capacity and condensed tannins yield. In addition, the extract was characterized by Fourier transform infrared spectroscopy and UV–Vis spectroscopy. Furthermore, extraction kinetics were modeled, and mass transfer mechanisms were studied. The extraction condition that maximizes extraction yields was defined at 50 °C, with a solid–liquid ratio of 1/10 and with an ethanol concentration of 50%. The condensed tannins yield was 4.01 g catechin equivalent (CE)/100 g pine bark dry base (d.b.), the total extractive yield was 9.83 g extract/100 g pine bark d.b. and the Stiasny number was 77. The extract showed a FRAP antioxidant concentration of 20.89 mmol ascorbic acid equivalent (AAE)/100 g pine bark d.b and 0.35 mmol trolox (TRE)/g pine bark d.b. for ABTS assay. The results showed that extended Fick’s law was adequate to describe the extraction kinetics. The extraction did not significantly affect the calorific value of bark (21 kJ/g d.b.). After extraction, the ashes were reduced by 13% and potassium (K) by 48%. The extraction of Pinus taeda to obtain phenolic content is technically feasible, and this paper provides the scientific ground for further scaling the process.
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