Determination of the degree of polymerisation of fructans from rye-grass and chicory using MALDI-TOF Mass Spectrometry and Gel Permeation Chromatography coupled to multiangle laser light scattering

This study is concerned with the determination of the degree of polymerisation (DP) of fructans from chicory and rye-grass (Lolium perenne L.) using Gel Permeation Chromatography coupled to multiangle laser light scattering and refractive index detectors (GPC / MALLS) and Matrix-Assisted Laser Desorption/Ionisation Time of Flight Mass Spectrometry (MALDI-TOF MS). The results show that fructans isolated from ryegrass have a DP in the range 2 - >100 and the commercially produced fructans derived from chicory have a DP in range 2 - 61. It has been demonstrated that MALDI-TOF MS is particularly effective at determining the DP of low molar mass material but is less effective for detecting the presence of high DP molecules. On the other hand GPC / MALLS is able to provide a much broader range of DP values although it is less sensitive at very low DP. It has been shown that the two techniques give complementary information thus providing a more accurate estimate of the overall DP of the fructan molecules