Abstract :
[en] Prebiotics are non-digestible food ingredients that beneficially affect the host health by stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and moreover can have systemic effects on metabolism regulation. Recent studies have pointed out the certain links between their structure (DP, types of linkage, sequence) and the specificity and intensity of their effects on host health. Therefore, the knowledge of the exact composition of prebiotic preparations has become a crucial step in the development of new products. Amongst these prebiotics, isomaltooligosaccharides (IMO), produced enzymatically from hydrolyzed starch, are the most developed in Asia thanks to their many favourable properties for application in food industry. However, their full characterization hasn’t been achieved yet.
In the present thesis, an HPAEC-PAD method has been set up in order to quantify the IMO present in syrups. Moreover, this step-forward analytical method permitted us to point out the presence of unknown IMO. Two structural determination methods were then set up and applied. PGC-LC-ESI-IT-MS2 including a chromatographic separation on a porous graphitized carbon column and producing MS2 fragment ion profiles specific to the linkage position proved to be promising but delicate for certain combination of linkage, while 1D and 2D NMR experiments give unambiguous structural determinations but need a preliminary chromatographic preparation step.
Moreover, two enzymes from different families (a glucosyl-transferase and an α-glucosidase) were tested on maltose individually or in combination. The IMO kinetics of formation and mixtures obtained were compared with a view to produce IMO preparations with singular profiles.
Finally, a new original method was set up to convert deleterious digestible saccharides, present in IMO preparations, into gluconic acid which presents various advantageous techno-functional properties as well as nutritional properties, in particular, prebiotic.
