Physicochemical and Gelatinization Properties of Starches Separated from Various Rice Cultivars

Morphological, viscoelastic, hydration, pasting, and thermal properties of starches separated from 10 different rice cultivars were investigated. Upon gelatinization, the G' values of the rice starch pastes ranged from 37.4 to 2057 Pa at 25 °C, and remarkably, the magnitude depended on the starch varieties. The rheological behavior during gelatinization upon heating brought out differences in onset in G' and degree of steepness. The cultivar with high amylose content (Goami) showed the lowest critical strain (γ(c)), whereas the cultivars with low amylose content (Boseokchal and Shinseonchal) possessed the highest γ(c). The amylose content in rice starches affected their pasting properties; the sample possessing the highest amylose content showed the highest final viscosity and setback value, whereas waxy starch samples displayed low final viscosity and setback value. The onset gelatinization temperatures of the starches from 10 rice cultivars ranged between 57.9 and 64.4 °C. The amylose content was fairly correlated to hydration and pasting properties of rice starches but did not correlate well with viscoelastic and thermal characteristics. The combined analysis of hydration, pasting, viscoelastic, and thermal data of the rice starches is useful in fully understanding their behavior and in addressing the processability for food applications.

Rice flour has potential applications in various food products. The physicochemical properties of rice flour are dependent on its variety, which affects the quality of the final products. In this study, the combined analysis including hydration, pasting, viscoelastic, and thermal properties of rice flour could afford information for preparing a particular product such as bread and noodle.