Kinetics of polyphenol extraction from wood chips in wine model solutions: effect of chip amount and botanical species

Abstract

The extraction of polyphenols from wood chips into a wine model system was described using kinetics, over a period of 20 days. The wood chips tested were made from oak (Quercus alba), false acacia (Robinia pseudoacacia) and cherry (Prunus avium) wood. Kinetics were established using nonlinear regression and the leaching of polyphenols into the liquid model systems was found to obey a second-order model. The determination of basic kinetic parameters enabled the identification of leaching trends and comparison among the difference wood species used, as well as determination of the effect of the amount of chips added. Oak chips were found to enrich the model wine in polyphenolic substances significantly more compared with either acacia or cherry. Furthermore, the wine model treated with oak chips displayed a much higher reducing power on day 20 of the treatment. The correlation of the total polyphenol concentration at saturation with the amount of chips added, using nonlinear regression, revealed that in every case the maximum concentration of total polyphenols attained was linked with the amount of chips by a three-parameter exponential growth function. Possible differences pertaining to wood botanical species and polyphenolic load are discussed on the grounds of theoretical considerations for diffusion. Copyright © 2015 The Institute of Brewing & Distilling