The FT–IR spectra of fructan – inulin (RAFTILINE), widely applied in the food industry and crystalline fructose as the main component of fructans, were studied. Special interest was to study the spectra of the levan precipitate and fructan syrup – produced byZymomonas mobilisduring the fermentation on sucrose–based medium.It was shown that levan precipitate and fructose syrup does not contain lipids and nucleic acids. Levan precipitate consists of ∼93% of fructose and admixture of glucose, mannan and enzyme – levansucrase. Fructan polymer inulin consists principally of linear chains of fructosyl units linked by aβ(2–1) bonds ended by a glycosyl unit. The links between the molecules are of a very special type: theβ(2–1) form (2) [8]. The bacterial fructans of the levan type are high molecular weight polymers, i.e., they are composed ofβ–(2,6)–ructosyl–fructose linked molecules and side chains [17]. The FT–IR spectra of levan, apart from inulin’s, in the carbohydrate region 900–1200 cm–1, shows overlapping broad band with maximum at ∼1030 cm–1and stronger absorption at ∼940 cm–1. The differences in both spectra could be caused by different structure and glucose, sucrose and mannan influence.

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Purpose -The aim of this study was to evaluate the influence of temperature and action time on the extraction rate of carbohydrates of Jerusalem artichoke concentrate powder and inactivation of inulin during boiling and sterilization. Design/methodology/approach -Water suspension of Jerusalem artichoke concentrate (5 g/ 100 ml) at 25, 50 and 100 C was tested after 5, 15, 30 and 60 min to determine the content of inulin, glucose, fructose and sucrose and evaluate the extraction rate. The stability of inulin was studied after boiling and sterilization at 120 C during 1, 2 and 3 h. The extraction rate was evaluated by Fourier-Transform Infrared (FT-IR) spectroscopy as well. Findings -It was shown that extraction of soluble carbohydrates -fructose, glucose, sucrose and inulin, from water suspension of Jerusalem artichoke concentrate was practically completed in 5 min at 25 C. The extraction rate was not significantly influenced by temperatures lower than 100 C. Inulin was stable during boiling for 1 h but sterilization for 1 h caused significant losses. Infrared spectral analysis of soluble and insoluble fractions showed that inulin was practically fully extracted. Originality/value -The paper shows that inulin can be easily extracted from Jerusalem artichoke concentrate powder even at 25 C and it maintains for 60 min at temperatures up to 100 C, nevertheless boiling or sterilization at higher temperatures for longer time causes significant loses of inulin and consequently the functional quality of Jerusalem artichoke powder. These results must be taken into account when applying inulin concentrates as functional food components.

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