Description of Microstructural Changes in Wheat Flour and Flour Components during Hydration by using Environmental Scanning Electron Microscopy

Abstract

The initial microstructures of two wheat flours (hard wheat flour and soft wheat flour) and flour components (starch, gluten, soluble pentosans and insoluble pentosans) were observed by scanning electron microscopy (SEM) and the changes in microstructure during hydration were described using environmental SEM (ESEM). SEM images permitted observation of the classical microstructure of wheat flour particles and starch granules. The initial microstructure of the purified fractions of flour components (gluten, soluble pentosans and insoluble pentosans) seemed largely dependent on the purification techniques, and could not thus directly be used to describe their in situ behavior during flour processing. ESEM observations of wheat flours and flour components during hydration first demonstrated slight changes in surface of particles that we associated to apparent swelling effects. The formation of a continuous aqueous phase between particles was observed for long hydration times.