Effect of high pressure on the physical properties of barley starch

The kinetics of the high-pressure gelatinization of barley starch suspensions at two different concentrations (10 and 25%) were studied in the pressure range 400–550 MPa. The pressure-treated samples were examined using rheological methods, microscopy and differential scanning calorimetry (DSC). The rheological properties, the microstructure and loss of birefringence, as well as the melting of amylopectin crystals as determined by DSC, were all both pressure- and time-dependent. For the 10% suspension, only a slight increase in viscosity was observed, while a strong paste with a creamy texture and a maximum storage modulus of approximately 23 kPa was formed during pressurisation of the 25% suspension. The rheological properties and the microstructure of the pressure-treated samples were different from those of the heat-treated samples. The starch granules remained intact after the pressure treatment and no leaching of amylose was observed. The retrogradation of pressure-induced gels was investigated by DSC and was shown to be similar to that of a heat-induced gel.