Lactobacillus reuteri strain (E81) is an alpha glucan producer from traditional sourdough and the physicochemical characteristics of this glucan was determined in this study. The HPLC analysis confirmed the presence of glucose as the only sugar monomer in the repeating structure of this exopolysaccharide (EPS). The functional groups within the glucan structure was detected by FTIR analysis. The scanning electron microscopy (SEM) analysis demonstrated the web-like branched structure of the glucan. Morphological characterisation of the glucan E81 by atomic force microscopy (AFM) analysis showed clear roundness lumps and chains. Importantly, thermal characteristics of glucan E81 determined by thermogram analysis (TGA) and differential scanning calorimeter (DSC) analysis revealed that glucan E81 has a melting point of 290 degrees C making it promising to be used in thermal processed foods including sourdough bread.