Optimization of conventional and ultrasound assisted extraction of inulin from gembili tubers (Dioscorea esculenta L.) using response surface methodology (RSM)

This study aim is to optimize the condition of conventional and ultrasound assisted extraction of inulin from Gembili (Dioscoreaesculenta L.). Optimization was performed using Response Surface Methodology (RSM). Inulin determination was done using UV-Vis spectrophotometry method which has validated on the preliminary study. RSM designed applied Central Composite Design (CCD) 33 using three-factor-three-level. Variables optimized were extraction time (X1), solvent to sample (water at temperature of 50°C) ratio (v/w) (X2) and extraction batch (X3). The quadratic model well fitted for response in both conventional and ultrasound assisted extraction method. Conventional method revealed higher inulin concentration on optimal extraction condition than ultrasound assisted extraction. The optimal extraction conditions of conventional method were achieved at the extraction time of 14.4 minutes; sample to solvent ratio of 1:18.18 (w/v); and extraction batch of 2.9. Furthermore, optimal extract contained inulin of 23.21% (w/w).