Applied Engineering in Agriculture Vol. 20(4): 487−494 2004 American Society of Agricultural Engineers ISSN 0883−8542 487 AIR AND RICE PROPERTY PROFILES WITHIN

ABSTRACT. Post−harvest processes such as drying can influence rice quality. Drying experiments conducted at the laboratory scale have been used to formulate a hypothesis explaining rice quality reductions; this work needed to be extended and applied to drying conditions encountered at the commercial level. A commercial cross−flow dryer was tested during the 2001 and 2002 rice harvest. The objectives were to record air temperature and relative humidity (RH) data at strategic locations throughout the dryer, obtain samples for rice moisture content (MC) and head rice yield (HRY) analysis at the end of each drying run from sampling locations within the rice column, and determine if rice experienced temperatures above its glass transition temperature (Tg). Above the first grain exchanger, air entering the rice column decreased rapidly in temperature while correspondingly increasing in RH as it passed through the column. However, after passing through the exchanger, lower air temperatures and higher RHs were observed near the hot air plenum (HAP). Rice samples collected next to the HAP showed that in some test runs, over−drying damaged a portion of the rice. For these test runs, rice experienced temperatures well above Tg. For those test runs dried at lower temperatures in which rice did not exceed Tg, negligible HRY reductions were observed