500 g tubers were taken randomly from each batch and chopped into small pieces. Inulin was extracted in hot distilled water according to Gao's methods with minor modification (Gao, Peng, & Xu, 2009). Firstly, the samples were boiled for 5 min to eliminate enzymes. Then they were stoved at 60 °C for 7 h and smashed with a grinder. The sample power was boiled in deionized water at 90 °C for 40 min twice and filtered. Ca(OH)2 was added to the filtrate until pH reached 11 to remove the protein, and H3PO4 was added until pH was 8 to remove the redundant Ca(OH)2. Then 30% H2O2 (v/v 3%) were used to bleach the solution. Finally, the inulin powder was collected by precipitation with excess ethanol and freeze dried at −40 °C.