Characterization of oligodextran produced by Leuconostoc mesenteroides SF3 and its effect on film-forming properties of chitosan

Oligodextrans (ODx) are exopolysaccharides (EPS) of low molecular weight (M_w <40 kDa) that have been of importance in food formulation due to their prebiotic activity. The way to generate ODx is through the acidic or enzymatic hydrolysis of high molecular weight dextrans (M_w>40 kDa), which are produced by bacterial strains (e.g., Leuconostoc mesenteroides) or their isolated enzymes. Since ODx are fragments of dextrans, their characteristics, such as molecular weight, main chain linearity (with α-(1→6) linkages), branches (with α-(1→2), α-(1→3), or α-(1→4) linkages) and their proportion in the molecule, are totally dependent on the producing strain. However, the modification of the ODx structure conducts to the variation of its properties (e.g., physicochemical, morphological, and rheological) and therefore its application is somewhat restricted when compared to a commercial dextran. The work aims to demonstrate the capacity of a new ODx, synthesized directly by Leuconostoc mesenteroides SF3, as a packaging material, with the idea of extending its application. For this, the ODx were characterized in a calorimetric and rheological manner; mixtures of the ODx (from 0 up to 4% w/v) and chitosan (CS: 1% w/v) were analyzed for viscosity to evaluate the interaction between the EPS and the filmogenic agent; finally, the morphology of the ODx/CS films was analyzed. The results show that the ODx and CS mixtures maintain the viscosity of the pure CS and significantly improve the morphology of the films. In such a way, this initial assessment shows the potential that ODx have as film former; however, a more exhaustive characterization is necessary to be able to evaluate their application as a packaging material directly in food.