| Abstract
| - Wheat starch suspensions in water (5% dry matter) were subjected to various pressures (0.1−600MPa) and temperatures (−20 to 96 °C) for 15 min. The gelatinization rate was measured aftertreatment by using microscopic measurements of the loss of birefringence of the granules. Thismethod was previously calibrated by differential scanning calorimetry. Curves of isogelatinizationwere found to be quite similar to a pressure−temperature (P−T) diagram of unfolding proteins.Results were first analyzed by considering the thermodynamic aspects related to the dT/dP curveshifts. On the basis of equations already shown for proteins, the P−T gelatinization diagram ofwheat starch would show different kinds of thermal contributions, suggesting endothermic, athermic,or exothermic melting reactions. Second, as a practical consequence, these previous P−T areascorresponded to specific gelatinization conditions as confirmed by hydration evaluation measuredby starch swelling index. Depending on the pressure−temperature conditions, gelatinization wouldinvolve hydration. Lowering the pressure and temperature resulted in a complete gelatinizationwith less hydration in comparison with a thermal treatment at atmospheric pressure. A hydrationmodel based on an energetic approach was proposed. Keywords: Starch gelatinization; high hydrostatic pressure; phase diagram; hydration
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