Abstract
A more simple methodology of producing parboiled rice is subject to be investigated in this work with proposed the method, the gelatinization of rice starch, commonly taking place at the steaming step in the traditional process, and drying are combined and replaced by a hot air fluidized bed dryer. A pilot-scale continuous fluidized bed, with a maximum capacity of 140-150 kg/h, has been designed, constructed and tested. Suphanburi 90 paddy variety with high amylose content was dipped into hot water at temperatures of 70, 80, 83°C for 4.0, 3.3, 3.2 h, respectively, to get the moisture content around 47-55% db and dried at 150-170°C using air speed of 3.5 m/s. The paddy bed depth within the dryer was 3 and 5 cm. In the dryer operation, the exhaust air was fully recycled and reheated again by 30 kW electrical heaters to the desired temperature. The experimental result has shown that parboiled rice with a different degree of starch gelatinization could be produced by this technique. The degree ranged between 80-100% as examined by differential scanning calorimeter. The exit moisture content was given in a range of 14-21% db, relying on the drying temperature and soaking time. The aforementioned exit moisture contents were not a detrimental effect on head rice yield although the tempering was not included. The head rice yield was given in the range of 59-66%, depending on the degree of starch gelatinization. The starch granules lost their original shape as revealed by scanning electron microscope.
Highlights
Rice parboiling is a method for prolonging rice and provides more nutritious values [1] such as more vitamins B and some minerals
The conventional hydrothermal process for parboiled rice consists of 3 main steps, soaking, steaming and drying
The soaking step is usually applied to enhance water diffusion into the kernel. It can make the starch granules swell. It is the main step for starch gelatinization
Summary
Rice parboiling is a method for prolonging rice and provides more nutritious values [1] such as more vitamins B and some minerals. The conventional hydrothermal process for parboiled rice consists of 3 main steps, soaking, steaming and drying. The soaking step is usually applied to enhance water diffusion into the kernel. It can make the starch granules swell. The parboiling method involves high steam pressure and temperature to gelatinize rice starch. It was found that at initial moisture content of paddy 42 ± 1% db and the hot air temperature of 170°C, paddy could achieve complete gelatinization, due to the feature of volumetric heating. Many studies focused on drying agricultural products [12] and a combination of microwave with hot air has shown significant improvement in operating cost and product quality [13], and has made parboiling process more efficient time [14,15,16]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
