Characterization of Inulin from Local Red Dahlia (Dahlia sp. L) Tubers by Infrared Spectroscopy

Inulin consists of soluble dietary fiber and insoluble dietary fiber, which is undigested carbohydrate produced by inulin extraction from local red dahlia tuber (Dahlia sp. L). Extraction of inulin was carried out through gelatinization by heating at a temperature of 90 °C for 30 minutes at pH 5 (control) and 10, respectively, then precipitated with ethanol to obtain inulin and continued with characterization by infrared spectroscopy (FT-IR). Based on FT-IR spectral analysis, the results showed characteristic absorption bands of inulin structure, OH stretch (3350 cm-1) and carbonyl (1645 cm-1). In addition, four characteristic regions can be distinguished from 3600 to 2500 cm-1, 2500 to 1550 cm-1, 1500 to 900 cm-1 and under 900 cm-1. The difference of infrared spectra obtained from each sample of inulin could be caused by different structure and influence of glucose, sucrose and mannan existed in inulin and the purification stage during treatment in alkaline condition.