Effect of temperatures on inulobiose and inulooligosaccharides in burdock roots during storage

The variation of inulobiose, inulotrose and other higher inulo-n-oses in burdock roots stored at 0, 15 and 20 °C during six weeks was investigated. Results showed that at 15 and 20 °C, inulobiose appeared after three day storage and then it increased progressively to 2.03 and 2.72 mg/g dry weight (DW) after 42 days, while inulotriose, inulotetraose, inulopentaose, inulohexaose and inuloheptaose appeared after one week and increased also progressively, and were 1.81 and 2.30, 1.92 and 2.12, 1.52 and 1.89, 1.18 and 2.14, and 1.45 and 3.75 mg/g DW, respectively. At 0 °C, the different inulooligosaccharides (IOSs) increased sharply after the second week but inulobiose and inulotriose decreased slightly after five weeks. However, their contents were much higher than those observed at 15 and 20 °C. This suggests that low temperature induced strongly the hydrolysis of inulin and formation of IOSs in burdock root suggesting that this reaction would not be the result of a putative endo-inulinase but results from the activity of fructan:fructan 1-fructosyltransferase (1-FFT).