Evaluation of the mechanical damage on wheat starch granules by SEM, ESEM, AFM and texture image analysis.

The effect of mechanical damage on wheat starch granules surface, at a microstructural level, was investigated by scanning electron microscopy (SEM), environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), and image textural analysis. The SEM and ESEM images of the native sample showed that the starch granules had smooth, flat surfaces and smooth edges. The samples with higher damaged starch content exhibited granular distortion, irregularity and less uniformity. The fractal dimension of contour parameter increased with mechanical damage, indicating that the surface irregularities quantitatively increased due to the damage. The surfaces of damaged granules showed depressions of different shapes and sizes. The roughness parameters and fractal dimension of the surface increased as a result of the mechanical damage. The surface of damaged granules showed higher entropy and lower homogeneity values when damaged starch increased. The results indicated that the mechanical process caused structural modifications at nano level.