Kinetics of high pressure facilitated starch gelatinisation in Thai glutinous rice

The combined effect of pressure and temperature on the rate of gelatinisation of starch present in Thai glutinous rice was investigated. Pressure was found to initiate gelatinisation when its value exceeded 200 MPa at ambient temperature. On the other hand, complete gelatinisation was observed at 500 and 600 MPa at 70 °C, when the rice was soaked in water under these conditions for 120 min. A first-order kinetic model describing the rate of gelatinisation was developed to estimate the values of the rate constants as a function of pressure and temperature in the range: 0.1–600 MPa and 20–70 °C. The model, based on the well-known Arrhenius and Eyring equations, assumed the formlnk=lnk0-EaRT-ΔVRTPThe constants k0, Ea and ΔV were found to take values: 31.19 s−1, 37.89 kJ mol−1 and −9.98 cm3 mol−1, respectively. It was further noted that the extent of gelatinisation occurring at any time, temperature and pressure, could be exclusively correlated with the grain moisture content.