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United States Department of Agriculture

Agricultural Research Service

Research Project: New Sustainable Processing Technologies to Produce Healthy, Value-Added Foods from Specialty Crops and their Co-Products

Location: Healthy Processed Foods Research

Title: Moisture removal characteristics of thin layer rough rice under sequenced infrared radiation heating and cooling

Authors
item Khir, Ragab -
item Pan, Zhongli
item Thompson, James -
item El-Sayed, Adel -
item Hartsough, Bruce -
item El-Amir, Mohamed -

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 20, 2012
Publication Date: August 8, 2012
Citation: Khir, R., Pan, Z., Thompson, J., El-Sayed, A., Hartsough, B., El-Amir, M. 2012. Moisture removal characteristics of thin layer rough rice under sequenced infrared radiation heating and cooling. Journal of Food Processing and Preservation. DOI:10.1111/j.1745-4549.2012.00791.x.

Interpretive Summary: To design efficient infrared (IR) dryers for rough rice, it is important to optimize the operating parameters of an IR dryer to achieve high heating rate, fast drying and high quality end-products. This research studied the effect of infrared intensity and various cooling conditions on drying rate. The obtained results revealed that IR heating followed by cooling could be an effective approach for designing new IR rough rice dryers with improved processing efficiency.

Technical Abstract: Rice drying with infrared (IR) radiation has been investigated during recent years and showed promising potential with improved quality and energy efficiency. The objective of this study was to further investigate the moisture removal characteristics of thin layer rough rice heated by IR and cooled with various methods, including natural cooling, forced air cooling and vacuum cooling. Rewetted rough rice samples with four different moisture contents (MCs), 16.7, 20.5, 23.6 and 25.7% (wb), were used for this study. Thin layer rough rice samples were heated using a catalytic IR emitter for four exposure times, 30, 60, 90, and 120 s under four different radiation intensities, 3616, 4023, 4685, and 5348 W/m2. The effects of heating time, radiation intensity, initial MC and cooling method on moisture removal were determined. High heating rate and moisture removal were achieved during the IR heating period. After heating, more moisture removal was achieved during the cooling period. The achieved grain temperatures ranged from 35.1ºC to 68.4ºC under the tested heating conditions. The vacuum and forced air cooling methods removed more moisture than did the natural cooling. When rice with 25.7% MC was heated by IR, moisture content was reduced by 3.2, 3.5, and 3.8 percentage points for rice heated to 63.5ºC at the IR intensity of 5348 W/m2 for 120s followed by natural cooling for 40 min, forced air cooling for 5 min and vacuum cooling for 10 min, respectively. We concluded that thin layer drying of rough rice with IR radiation followed by cooling could be an effective approach for achieving a large amount of moisture removal with a relatively short heating time.

Last Modified: 7/25/2014