Thermal and textural properties of extruded rice affect its cooking performances and the texture of the steamed extruded rice

Abstract

Extruded rice has increasingly gained popularity in the market due to its convenience and acceptable texture. The objective of this study was to understand how the physicochemical, thermal, and textural properties of the extruded rice affected its cooking properties and texture of the cooked one. It was found that air trapped in the grains during extrusion reduced the transparency of extruded rice. More air trapped in the grains reduced the true density of the extruded rice, which in turn decreased the hardness of extruded rice. A looser internal structure of extruded rice grain, as indicated by the lower true density, resulted in a faster hydration and shorter optimum cooking time. Extruded rices showed two thermal-transition peaks, with peak 1 from 93.3 °C to 112.8 °C and peak 2 from 107.5 °C to 132.5 °C. The increased hardness of extruded rice led to increases in its thermal-transition temperatures, longer optimum steaming time, and decreases in its water absorption and cooking loss, which resulted in an increase in the hardness and a reduction in the adhesiveness of the steamed one. This study provides insights into the key factors determining the eating quality of extruded rice, which is beneficial for food scientists in developing premium extruded rice.