Temperature and solvent effects on polyphenol extraction process from chestnut tree wood

Polyphenols are a group of chemical substances found in plants, characterized by the presence of more than one phenol unit or building block per molecule. Polyphenols are generally divided into hydrolysable tannins (gallic acid esters of glucose and other sugars) and phenylpropanoids, such as lignins, flavonoids, and condensed tannins. They are widely found in natural products, nowadays they are extensively used in food and beverage industry and in pharmaceutical and nutraceutical industry for their positive effects on human health. In conventional processes polyphenols are extracted from vegetable material using water as solvent in a temperature range from 40 to 90 degrees C. The aim of this work is to characterize chestnut tree wood in terms of total extractable polyphenols and assess the temperature and solvent type effects on the polyphenol extraction process. To this end, experimental data on equilibrium distribution of polyphenols between solid and liquid phases for different temperatures (ranging from 60 to 80 degrees C) and different solvent solutions (water and ethanol-water solutions) are reported. The obtained results have been correlated by means of Freundlich isotherm. Experimental data are also reported about the batch extraction kinetics of polyphenols from solid phase and analysed by a mathematical model to estimate the polyphenol diffusion coefficient inside the chestnut wood particles and the mass transfer coefficient in the liquid phase. (C) 2010 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.