Isolation and identification of inulooligosaccharides resulting from inulin hydrolysis

In this study, inulooligosaccharides (Fn-type inulin) resulting from the endo-inulinase hydrolysis of globe artichoke inulin were purified and characterized. The aim was to produce Fn oligomer standards with the intention of identifying them in the complex inulin chromatogram. Inulin was extracted from globe artichoke and presented a high average degree of polymerization (DP) of about 80 as determined by high-performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). This inulin was hydrolyzed by a commercial endo-inulinase yielding a product with a very high Fn/GFn molecule ratio, thus limiting the interference of GFn during the purification process. High-performance size exclusion chromatography was used to individually isolate and collect each retention peak corresponding to a specific oligomer. The purity of these fractions was checked by HPAEC-PAD and showed that relatively pure molecules were produced. Electrospray ionization mass spectrometry allowed the molecular weight determination of these purified oligomers and ascertained their DP as F2, F3 and F4. These F2–4 standards were used with glucose, fructose, sucrose and GF2–4 (commercially available) to spike commercial oligofructose products in order to determine the elution profile in the HPAEC-PAD chromatogram.