Determination of Viscoelastic and Physicochemical Interactions of Dextran Type Exopolysaccharides (EPS) with Different Starch Samples

In this study, the rheological properties of three distinct dextrans with different levels of (1 → 6)-linked α-D-glucose/(1 → 3)-linked α-D-glucose units from three lactic acid bacteria (LAB) strains were determined. Dextran PDER21 was further selected following the rheological measurements and its interactions with maize, wheat and waxy maize starches were determined by characterizing the viscoelastic and pasting properties of the dextran–starch mixtures. Fourier transform infrared (FTIR) spectroscopy analysis was also applied to unveil this interaction. The presence of dextran PDER21 in the standard maize starch increased the elastic behavior, while its increased amounts enhanced the elastic properties of wheat and waxy maize starches. The temperature sweep test showed the solid-like property of starch–dextran mixtures in the studied temperature range (4–70 °C). Dextran PDER21 affected the pasting properties of starches. Especially, high levels of the peak, through and final viscosity values were reached with the blends of standard maize starch–1% dextran, wheat starch–0.5% dextran and waxy maize starch–0.5% dextran PDER21. Finally, the interactions were also confirmed by FTIR analysis as no alterations in the starch FTIR spectra were observed at different levels of dextran in different starch samples.