Thermal processing of rice grains affects the physical properties of their pregelatinised rice flours

摘要

Waxy, low- and high-amylose rice were cooked at different temperatures (50, 70, 90 ℃) for different times (15, 30, 45 min). The microscopic, rheological and gel textural properties of resultant flours were investigated. There was a coarser and discontinuous honeycomb-like structure with formation of pores in rice flour with greater cooking degree. TG_(max) was positively correlated with cooking temperature and time. As cooking temperature increased, the G' values of pastes first increased and then decreased, whereas the opposite trend was observed for tan 5. Meanwhile, increased cooking temperature was responsible for increases in n values and caused drops in K and hysteresis area. As cooking time increased, the hardness and gumminess of gels from rice cooked were increased at lower temperature, but were decreased at higher temperature. Overall, cooking temperature was more important in determining the processing properties of rice flours than cooking time.