Pressure−Temperature Phase Transition Diagram for Wheat Starch

Abstract

Wheat starch suspensions in water (5% dry matter) were subjected to various pressures (0.1-600 MPa) and temperatures (-20 to 96 degrees C) for 15 min. The gelatinization rate was measured after treatment by using microscopic measurements of the loss of birefringence of the granules. This method was previously calibrated by differential scanning calorimetry. Curves of isogelatinization were 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 curve shifts. On the basis of equations already shown for proteins, the P-T gelatinization diagram of wheat starch would show different kinds of thermal contributions, suggesting endothermic, athermic, or exothermic melting reactions. Second, as a practical consequence, these previous P-T areas corresponded to specific gelatinization conditions as confirmed by hydration evaluation measured by starch swelling index. Depending on the pressure-temperature conditions, gelatinization would involve hydration. Lowering the pressure and temperature resulted in a complete gelatinization with less hydration in comparison with a thermal treatment at atmospheric pressure. A hydration model based on an energetic approach was proposed.

High Pressure Processing – a Database of Kinetic Information

“…However, the pressure effect is by far smaller when the treatment temperature is approaching the gelatinization temperature at the atmospheric pressure. Wheat starch is different in that sense because the temperature required to irreversibly change the native granule structure is already decreased markedly when the pressure increases by 50 MPa [100]. [47], B. amyloliquefaciens [48], B. stearothermophilus [49], C. botulinum [50] and C. sporogenes [51] after 5 min isothermal/isobaric treatment.…”

Recent Processing Methods for Preparing Starch‐based Bioproducts

“…Increasing screw speed, and hence shear (or SME), has also been found to increase the extent of starch gelatinization or melting (Xie et al ., 2006a ). Increasing pressure has been found to decrease the melting temperature of starch in water at a rate of 0.075 °C/MPa (Douzals et al ., 2001 ). Thus, the effect of pressure is expected to be rather small at typical extrusion pressures of ~10 MPa.…”

“…Effects of pressure-temperature combinations on the gelatinization of wheat starch granules were determined, and a pressure-temperature gelatinization diagram was constructed (Douzals et al ., 2001 ). Similarities between starch gelatinization and protein unfolding under pressure were observed.…”

Food preservation by high pressure

“…However, the pressure effect is by far smaller when the treatment temperature is approaching the gelatinization temperature at atmospheric pressure. Wheat starch is different in that sense because the temperature required to irreversibly change the native granule structure is already decreased markedly when pressure is increases by 50 MPa (Douzals et al 2001). Fig.…”