Thermogravimetric study of water state in wheat starch gels obtained under high pressures.

Wheat starch gels containing 56.0% of water were obtained during thermal gelatinization under isobaric conditions at different pressures ranging from 0.5 to 100 MPa. Thermogravimetric analysis allowed determination of pressure influence on water behavior in gel matrix. The vaporization rate indicated that water is released in two main steps. The first step corresponds to the diffusion of the water fraction (so-called nonbound water) from the porous structure of the amylose gel located between partially swollen starch granules. However, the second step that appears at higher temperature is related to the desorption of water molecules (bound water), included in the swollen granules. It was observed that the most important influence of pressure on water partitioning in the starch gel took place over a pressure range from 0.5 to 10 MPa. The results obtained indicate that pressure is a thermodynamical parameter, which stabilizes the native state of starch granules.