Inulin extraction from common inulin-containing plant sources

Currently there is a growing interest from the food industry in obtaining inulin for its possible use in the elaboration of functional foods. A set of optimum extraction conditions was developed for the recovery of inulin plus fructo-oligosaccharides (FOS) from several common inulin-containing plant sources, like chicory roots (Cichorium intybus L.) and Jerusalem artichoke tubers (Helianthus tuberosus L.), as well as from novel sources like globe artichoke inflorescence (Cynara cardunculus L.) and its by-product. Optimal conditions for temperature (60-80 degrees C), time (20-60 min) and solvent to solid ratio (10-40 mL/g) were estimated in order to maximize inulin plus FOS extraction by using response surface methodology (RSM) with a Box-Behnken design. Inulin plus FOS were estimated colorimetrically by difference between total carbohydrate and reducing sugar contents for the optimization. Moreover, the profile of inulin and low molecular weight carbohydrates was studied in optimized plant extracts by HPLC. Inulin in raw samples and optimal extracts were further characterized by Fourier Transformed Infrared spectroscopy. According to response surface methodology model, optimal conditions for inulin plus FOS extraction depended on plant source and were achieved at a solvent to solid ratio of 27.8-37.4 mL/g, from 62-80 degrees C and a variable time of 22-60 min. The highest inulin plus FOS contents were achieved in chicory root (70.5 g/100 g dry weight) and Jerusalem artichoke tuber (81.1 g/100 g dry weight), and the lowest ones were attained in globe artichoke by-product (4.2 g/100 g). Nevertheless, its high availability and low cost would support this novel globe artichoke by-product as an alternative and valuable source of inulin and FOS for the food industry. At the same time their reuse as potential prebiotic ingredients would contribute to the circular economy.