Study of the Red Rice Parboilization Process

Abstract

This research aimed to obtain information on hydrated red rice at different temperatures (45, 55, 65 and 75 °C) for 7 hours. During the hydration process, the structural and morphological modifications of red rice were observed, as well as the hydration kinetics by Peleg (1988), Cavalcanti-Mata & Duarte (2018) and Duarte & Cavalcanti Mata (2018) models. There were performed X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis in order to identify the type of crystallinity and to obtain images referring to the surfaces of the starch granules particles. The results identified by the XRD analysis that hydrated red rice is classified as type a starch. And the SEM analysis identified that there was a change in its morphological structure, providing the beginning of red rice starch gelatinization. The absorption kinetics showed that above 5 hours of hydration at 55, 65 and 75 °C, the red rice grain reaches 28% water content. Mathematical modeling proves that the models proposed by Cavalcanti & Duarte and Cavalcanti Mata & Duarte (2018) performed better than Peleg's model (1988), according to the statistical parameters evaluated (P, SE, DQM, and R²). The XRD and SEM results of red rice hydrated for 7 hours at 55 °C, autoclaved for 14, 22 and 30 minutes and dried at 50, 60 and 70 °C confirm parboiling process since the starchy structure of red rice was very distinct from the type A starch structure and confirmed the starch gelatinization.