Drying Characteristics and Quality of Rough Rice under Infrared Radiation Heating

Abstract

Infrared (IR) radiation heating could provide a high heating rate and rapid moisture removal for rough rice drying. The objective of this research was to investigate the effect of the drying bed thickness on drying characteristics and quality of rough rice subjected to IR heating. Samples of freshly harvested medium grain rice (M202 variety) with 20.5% and 23.8% (w.b.) moisture contents were used for this study. They were dried with two different radiation intensities (4685 and 5348 W m-2) and exposure times of 15, 30, 40, 60, 90, and 120 s for each drying bed thickness. The three tested drying bed thicknesses were single layer, 5 mm, and 10 mm. After IR drying, the samples were tempered for 4 h followed by natural cooling. The drying rate, moisture removal, and temperature of the rice were determined. The rice temperatures after the IR heating were in the range of 35.9°C to 71.4°C. The heating and drying rates decreased with the increase of bed thickness. Up to 2.2% of moisture was removed during natural cooling after tempering, without additional energy input. IR heating under tested conditions did not have adverse effects on rice sensory and milling quality, including total rice yield, head rice yield, and degree of milling of the dried rice. We concluded that a high heating rate, fast drying, and good rice quality can be achieved by IR heating of rough rice to about 60°C followed by tempering and natural cooling with a tested bed thickness up to 10 mm.

Study on the Variable-Temperature Drying Process of Corn Drying in an Industrial Corn-Drying System Equipped with a Self-Adaptive Control Heat Exchanger

“…Afzal et al also compared barley drying performance between far infrared convection drying and hot air drying; the results showed that far infrared convection drying could improve the drying rate and reduce the energy consumption, and the optimal radiation intensity was found to be 0.33 W/cm 2 [16]. Pan et al also reported that when fresh paddy with a thickness of 10 mm was heated up to 60 • C by far infrared drying technology, the moisture in wet paddy could be further removed under natural wind drying technology [17]. Obviously, it can be summarized from the above analyses that far infrared drying technology can be applied to grain drying.…”

Feasibility of Using a Multistage Drying Method Including Infrared Heating, Tempering and Sun Drying for Wet Paddy

“…Paddy is normally harvested at high moisture levels, higher than 14% (wet basis), which is not appropriate condition for storage due to quality deterioration [1,2,3]. Drying is usually considered as a common means to offer an appropriate moisture content of paddy.…”

“…Even though sun drying is still practiced largely unchanged from ancient times due to its low capital and operating costs and the fact that little expertise is needed, its disadvantages including slow or intermittent drying, contamination, large areas needed for shallow layers and unpredictable weather, have been encountered. As a result, many attempts have been made to develop drying technique to be served as an alternative method to dry wet paddy such as a conventional hot-air drying process in which it is typically dried by heated air [2]. Among various drying techniques, infrared (IR) radiation technology has been considered as one of potential alternatives to traditional heating methods for obtaining high-quality dried long-grain paddy [1].…”

“…Among various drying techniques, infrared (IR) radiation technology has been considered as one of potential alternatives to traditional heating methods for obtaining high-quality dried long-grain paddy [1]. The infrared drying has been recently employed in agro-industry due to its high thermal efficiency, simplicity of the required equipment and its installation [1,2]. Therefore, it has been used in many applications associated with conventional heating methods.…”