Effect of high-pressure microfluidization on the structure and properties of waxy rice starch

Abstract

Waxy rice starch-water suspensions (5, 15%) were subjected to high-pressure microfluidization treatment at 50 MPa, 100 MPa, and 150 MPa. The influence of microfluidizing pressure on the temperature, thermal properties, particle size and morphology of starch granules were investigated, with native waxy rice starch as a control sample. The temperatures of microfluidized starch slurries increased with the increase of the applied pressure and the rate was 0.12°C MPa-1 and 0.08°C MPa-1 for 5 and 15% starch concentration, respectively. However, the increasingtemperatures were below the gelatinization temperatures of waxy starch. Differential scanning calorimetry analysis showed a decrease in gelatinization temperatures (To, Tp) and gelatinization enthalpy (ΔHgel) with increasing homogenizing pressure. Laser scattering measurement of particle size showed an increase in the granule size at a homogenizing pressure of 150 MPa. Thiswas attributed to the gelatinization and aggregation of the starch granules. The morphology ofwaxy starch studied by scanning electron microscope showed that the waxy starch was partly gelatinized at the pressure of 100 and 150 MPa, and the gelatinized granules were tend to aggregate with each other, resulting in an increase of granule size.