Physicochemical characteristics of inulins obtained from Jerusalem artichoke (Helianthus tuberosus L.)

摘要

The physicochemical characteristics (thermal stability, glass transition temperature and degree of crystallinity) of inulins, obtained from the tubers of four varieties Jerusalem artichoke (Helianthus tuberosus L.) grown in Bulgaria—Energina, Verona, Topstar and Spindel, were investigated. The inulins obtained had molecular weight from 4,882 to 5,600 Da (degree of polymerization around 30 fructose units). The experimental data from differential scanning calorimetry showed that the glass transition temperature of inulins is between 51 °C and 55 °C. It was found that the first transition (due to evaporation of the unbound water) starts from 77 to 80 °C. The second transition phase started between 152 and 158 °C, and it determines the limit of inulin thermal stability. The data from differential thermal analysis confirmed the results of differential scanning calorimetry with slight differences in the starting temperatures and durations of the phase transitions. X-ray analysis showed that the degree of crystallinity of inulins is very low (except for Spindel inulin—21%).