Effects of High-Temperature Fluidized Bed Drying and Tempering on Kernel Cracking and Milling Quality of Vietnamese Rice Varieties

Studies on the effects of high-temperature fluidized bed drying and tempering on physical properties and milling quality of two long-grain freshly harvested Vietnamese rice varieties, A10 (321% wet basis moisture) and OM2717 (24.50.5% wet basis moisture), were undertaken. Rice samples were fluidized bed dried at 80 and 90C for 2.5 and 3.0min, then tempered at 75 and 86C for up to 1h, followed by final drying to below 14% moisture (wet basis) at 35C by thin-layer drying method. Head rice yield significantly improved with extended tempering time to 40min. Head rice yield tended to increase with decreasing cracked (fissured) kernels. The hardness and stiffness of sound fluidized bed dried rice kernels (in the range of 30-55N and 162-168N/mm, respectively) were higher than that of conventionally dried ones (thin layer dried at 35C). The color of milled rice was significantly (P0.05) affected by high-temperature fluidized bed drying, but the absolute change in the value was very small.