Effect of medium hydrostatic pressure on the properties of wheat flour main biopolymers

In our work, the effect of medium hydrostatic pressure on the properties of wheat flour's main ingredients, starch and proteins, is presented and discussed. The symbiotic effect of the different constituents via size exclusion chromatography, water binding, gelatinization experiments as well as atomic force microscopy measurements and X-ray diffraction is elucidated. From results of size exclusion chromatography and protein content analysis, prolamin fractions seemed to be most sensitive to pressure. Hydrostatic pressure, however, had a significant influence on the amount of bound water and gelatinization enthalpy, especially at moderate pressures and higher temperatures. In this case, an optimal interaction between macromolecules and water occurs. This was also confirmed by atomic force microscopy images and X-ray diffraction patterns. Amorphous and crystalline regions of starch granules were modified, depending on pressure and temperature. At medium pressure (200 MPa), water was pressed into the starch cavities remaining there, whereas higher pressure (600 MPa) led to complete flattening of the surface. With X-ray diffraction, it was shown that medium pressure had nearly no effect on molecular structure, whereas higher pressure caused thermal-like molecular modifications.