Effects of High-Pressure Treatment on Functional, Rheological, Thermal and Structural Properties of Thai Jasmine Rice Flour Dispersion

Abstract

Effect of high-pressure (300–600 MPa) and flour to water (F/W) ratio (1:1-1:4) on functional, rheological, thermal and structural properties of Thai Jasmine rice flour were investigated. Water holding capacity and water solubility index of high-pressure-treated rice samples increased linearly with pressure intensity. Pressure treatment significantly influenced the particle size distribution of flour. Thermal transitions and the mechanical property of pressure-treated samples were measured by DSC and rheometry, respectively. Starch gelatinization of rice flour is affected by both applied pressure and F/W ratio. The mechanical rigidity G′ of rice flour decreased with increasing F/W ratio and increased with the pressure level. The peak viscosity, hot paste viscosity and final viscosity decreased significantly with increasing pressure intensity. Fourier-transform infrared (FTIR) spectroscopy showed changes in the secondary structure of rice proteins and the sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) showed changes in the protein subunits that occurred after the pressure treatment. Practical Applications High pressure is a novel processing technology that transforms sol to gel and produces a desirable gel which is relatively softer than the thermal gel. Rice flour is currently studied extensively for development of food products for celiacs and an increasing demand from Asian consumers' for preparation of ethnic foods. Therefore, an application of pressure as a processing method to improve the quality of rice starch products would be possible.