Kinetics and thermodynamics of the solid-liquid extraction process of total polyphenols from barley

Abstract

a b s t r a c t Antioxidants derived from plants are widely used in dietary supplements and have been investigated for the prevention of diseases such as cancer, coronary heart disease and altitude sickness. In order to obtain the highest possible amount of bioactive compounds from plant material, effective extraction procedures are required. One of the most widely used extraction techniques which requires no toxic chemicals is solid-liquid extraction. Mathematical modelling of solid–liquid extraction processes is an important engi-neering tool in the design process in order to reduce energy, time and chemical reagents consumption. In agreement with that, the aim of this paper was determination of the best suited kinetic model for descrip-tion of the solid-liquid extraction of bioactive compounds from Asteraceae family plants. In this study, four most common representatives of Asteraceae family were chosen as subjects: camomile (Matricaria recutita L.), dandelion (Taraxacum officinale Web.), marigold (Calendula officinalis) and yarrow (Achillea millefolium L.). Initial extraction rate, extraction capacity, activation energy, Gibbs energy, enthalpy and entropy were determined for all of the four analysed plants. The highest extraction efficiency of total polyphenols content, antioxidants and extraction yield were achieved at the highest extraction temper-ature of T = 80 • C for all four plants used in this study. Obtained results for activation enthalpies indicated that the extraction processes were endothermic and Gibbs free energy of activation indicated that they were endergonic and not spontaneous.