Red rice drying and storage: Effects on technological properties and phenolic compounds of the raw and cooked grains

Abstract

The use of pigmented rice grains has increased in the food industry in recent years, however, the effects of post-harvest on chemical, physical and technological properties are poorly known. Pigmented rice grains were dried at temperatures between 40 and 100 °C, followed by storage for 12 months, to evaluate the technological properties and phenolic compounds of rice grains with red pericarp. The increase in drying temperature promoted reductions in head rice yield (HRY), soluble protein, cooking time, grain integrity after cooking, total free and bound phenolics, and total proanthocyanidins and increased electrical conductivity, defects, hardness, and rehydration index. The prolonged storage of grains dried at temperatures above 60 °C promoted an increase in electrical conductivity, defects, hardness and reduction of soluble protein, cooking time, and total free phenolics, possibly due to the formation of cracks in the grains and due to latent damage in grain storage. Therefore, it is recommended drying temperatures below 60 °C for the storage of red pericarp rice grains for adequate conditions of conservation of technological properties and phenolic compounds.