Characteristics of Flour and Starch Isolated from Red Rice Subjected to Different Drying Conditions

Abstract

Drying is a method used to reduce grain moisture and prolong safe storage. The objective of the study is to evaluate the changes in red rice flour and starch submitted to sun‐drying, continuous drying at 40 °C, continuous drying at 100 °C and intermittent drying. In general, the significant changes are found in continuous drying at 100 °C, followed by intermittent drying, continuous drying at 40 °C and sun‐drying. Continuous drying at 100 °C reduces starch extraction yield and increases residual protein, leading to starch with dark reddish stains. At higher temperatures, increases in TO and relative crystallinity and lower solubility, swelling power, ΔT occur. The flour gel presents higher values when intermittent drying is applied, differing from the starch gel, which higher hardness found at continuous drying method at 40 °C probably due to the macromolecules from rice pericarp. According to the increase in grain drying temperature, there are reductions in final viscosity and setback in the starch and increases in final viscosity and setback in the flour, attributed mainly to the high amount of protein. The parameters of RVA and texture demonstrates that the higher purity of the starch promotes a gel with greater stability in refrigeration.