Extraction of Fennel (Foeniculum vulgare) Seeds: Process Optimization and Antioxidant Capacity of the Extracts

G. Angelov and S. Boyadzhieva

Abstract
This paper presents the study on the extraction of bioactive substances from fennel seeds. The impact of the main process variables (solvent composition, liquid-to-solid ratio, temperature, contact time) on the concentration of the target substances (polyphenols and flavonoids) in the extracts is studied resulting in the selection of a set of operating parameters, at which their content is maximized. Extracts with higher concentration of target compounds demonstrate higher antioxidant capacity, which confirms the contribution of these substances to better antioxidant performance. The performance of two types of solvents is compared: water and ethanol-water mixtures, showing that water extraction produces more concentrated extracts with higher antioxidant capacity. The extraction kinetics is simulated using Peleg’s equation, and a good fit to experimental data is observed. Data for initial extraction rate and equilibrium concentrations is obtained. Based on the combination of experimental and simulation results, an equation is proposed for determination of antioxidant capacity of water extracts of fennel seeds when the phenolic concentration is known, and vice versa – calculation of concentration of polyphenolic compounds in extracts with known antioxidant capacity.

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Keywords
Foeniculum vulgare, polyphenols, flavonoids, process optimization, antioxidant capacity, Peleg’s equation