Air temperature and final grain moisture effects on drying time and milling quality in two types of fluidized bed dryer

摘要

Drying process is one of the important stages in paddy milling process and plays a key role in the product quality. In this modified the effects of air temperature (40°C, 50°C and 60°C) and final paddy grain moisture content (8-9%, 9-10% and 10-11% d.b.) were examined on the drying time and milling properties in fluidized bed dryer with two heating sources (infrared radiation and heater types). The experimental design was randomized complete design with factorial layout in which three levels of final paddy grain moisture content, three levels of air temperature and two types of dryers with three replications in each treatment. The results indicated that the lowest cracked grain (8.01%) was related to the air temperature of 40°C and the moisture content of 10%-11%; whereas the highest cracked grain percent (14.67%) was registered at the air temperature of 60°C and the moisture content of 8%-9%. The milling recovery decreased as the air temperature and final paddy grain moisture content increased. At each final paddy grain moisture content, the drying time decreased and broken rice increased significantly (P<0.01) as the air temperature increased from 40°C to 60°C, however the broken rice and drying time in infrared fluidized bed dryer was significantly (P<0.01) lower than those of the heater type one. The drying time in the infrared fluidized bed dryer was reduced by 67.7%, 70.0% and 75.4% compared to heater type fluidized bed dryer at the air temperatures of 40°C, 50°C and 60°C, respectively.