Microwave heating for accelerated aging of paddy and white rice.

Abstract

Microwave heating treatment (MWH) can be applied for accelerated rice aging. Two microwave powers (MWP) (1,000 and 2,000 W) and six exposure time (ET) (23, 26, 31, 41, 66, and 159 seconds) were applied to paddy (PD) and white rices (WR) of indica cultivar as potential accelerated rice aging agent. The newly harvested rice was sun dried to < 14% dry basis and then heated under MWH. The head rice yield (HRY), color and gel consistency were determined for microwave-treated and untreated sample (control). Furthermore, texture of cooked rice grains, pasting properties, and gel texture of rice paddy after optimum MWH (41 seconds) were further investigated. After 41 seconds of MWH (by two levels of MWP), the HRY of PD decreased ( 5 %) while other MWH conditions caused a larger decrease in HRY of PD, compared to the control sample, especially for higher MWP at 66 s (31.97%) and 159 s (74.78%). The cooking time of white rice (WR) was also decreased while that of PD increased, compared to the control sample. The gel consistency was increased and variously changed depends to the form of rice and ET. After MWH, the appearance of WR was whiter while the PD looked browner with increased on exposure time ET, compared to the control. The cooked rice from WR was more damaged and less uniformed compared to PD. Further investigation on optimum condition for PD (41s) indicated increase in hardness of cooked rice grains, pasting properties and soft gel when compared to the control sample. The effect of MWP and ET was dissimilar between PD and WR on different rice aging properties, in which the PD seemed more effective to be applied as accelerating rice aging agent.