Investigation of Thai plants for potential sources of inulin-type fructans

Several studies have found wide distributions of natural inulin and its fractions as fructo-oligosaccharide (FOS) in varieties of plants, starchy roots, fruits, and vegetables. However, there is a lack of information of their abundance in foods consumed in Thailand. Therefore, the objective of this study was to determine inulin-type fructans, FOS (1-kestose (1-kestotriose; GF2), nystose (1,1-kestotetraose; GF3), and 1F-β-fructofuranosylnystose (1,1,1-kestopentaose; GF4)) and sugars (glucose, fructose and sucrose) in potential food sources. For a preliminary study, 47 varieties of Thai plant foods, distributing in five food groups, were selected and purchased from one representative market. Inulin-type fructans, FOS and total sugars were extracted following the method 997.08 of AOAC, and determined by gas chromatography. Potential food sources of inulin-type fructans and FOS were identified. Another two sets of these samples were purchased randomly from other two representative markets and the same analyses were conducted. High levels of inulin-type fructans was found in great headed garlic, Chinese garlic, common garlic and Jerusalem artichoke (Kaentawan) (29.2 ± 5.62, 24.3 ± 1.94, 22.4 ± 2.86 and 19.4 ± 1.04 g/100 g fresh weight (FW), respectively), with the medium level in shallot and red onion (8.86 ± 0.75 and 3.56 ± 0.95 g/100 g FW, respectively). Highest level of FOS (5.18 ± 0.04 g/100 g FW) was found in Jerusalem artichoke.