สำนักราชบัณฑิตยสภา

The Journal of the Royal Institute of Thailand Vol. 30 No. 2 Apr.-Jun. 2005 378 °“√æ— ≤𓇧√◊Ë Õßµâ π·∫∫Õ∫·Àâ ߢ⠓«π÷Ë ß ·∫∫ø≈Ÿ Õ‘ ‰¥´å ‡∫¥‚¥¬„™â ‰ÕπÈ ”√â Õ𬫥¬‘Ë ß Abstract Development of a Superheated-steam-fluidized-bed Dryer for Parboiled Rice Wathanyoo Rordprapat Adisak Nathakaranakule Warunee Tia Somchart Soponronnarit Fellow of the Academy of Science, The Royal Institute, Thailand Due to possessing a large number of componential machines and long operating time, the present procedure for producing parboiled rice requires much investment and operating costs. This research is therefore aimed at developing a 100 kg/h prototype for fluidized bed paddy drying using superheated steam. The experiments were set up by pre-soaking paddy in hot water with the initial temperatures of 80 and 70 o C for 3 and 4 hours to obtain the moisture contents of 28.7 and 31.7% w.b. respectively. The paddy was then dried at the temperatures in the range 128 - 164 o C, with the bed height of 8 cm, the super- ficial velocity of 3.8 m/s, and the residence times of 4 - 5 minutes. After drying, the moisture contents were reduced to 17.9 - 22.8% w.b. and the finished rice was characterized as parboiled rice. When com- pared to the reference rice, the head rice yield was higher while rice whiteness was lower and decreased with increasing temperature. For pasting properties, peak and final viscosities were lower than those of the reference rice. With the above mentioned process, decreasedmoisture content and a gelatinized paddy starch simultaneously occurs. Consequently, steaming and drying processes can be merged into a single stage; resulting in the reduced investment cost and operating time when compared with the production system of the commercial parboiled rice. Key words : soaking, parboiled rice, gelatinization, fluidization, physical properties, superheated steam