|DING, CHAO - Nanjing Agricultural University|
|KHIR, RAGAB - University Of California|
|ZHAO, LIMING - Shanghai Institute Of Technology|
|TU, KANG - Nanjing Agricultural University|
|EL-MASHAD, HAMED - University Of California|
Submitted to: Food and Bioprocess Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2014
Publication Date: 5/4/2015
Citation: Ding, C., Khir, R., Pan, Z., Zhao, L., Tu, K., El-Mashad, H., Mchugh, T.H. 2015. Improvement in shelf life of rough and brown rice using infrared radiation heating. Food and Bioprocess Technology. 8(5):1149-1159. doi: 10.1007/s11947-015-1480-5.
Interpretive Summary: Though the infrared drying (IRD) characteristics, moisture diffusivity, milling quality, and disinfestation effect of rough rice were widely investigated, the effect of infrared drying on the storage stability of rough and brown rice has yet to be studied. The objectives of this research were to determine drying characteristics and milling quality of rice dried using IR heating and to investigate the impact of IRD on the storage stability of rough and brown rice when compared to rice dried by hot air and ambient air. The studies showed significant improvement in rough and brown rice stability during storage when rough rice was dried using IR heating to temperature of 60 °C followed by tempering for 4 h and natural cooling. Kinetic models for the change of free fatty acid in rough and brown rice during storage were also developed. The research demonstrated the potential of IR drying treatment in extending shelf life and reducing cost of storing brown rice.
Technical Abstract: The objective of this study was to investigate the effect of IR heating and tempering treatments on storage stability of rough and brown rice. Samples of freshly harvested medium grain rice variety M206 with initial moisture content of 25.03±0.21% (d.b.) were used. They were dried using infrared (IR), hot air at 43 °C and ambient air for comparison. For IR drying, rice were heated to temperature of 60 °C under radiation intensity of 4685 W/m-26, followed by 4 h tempering and natural cooling. The dried samples were divided into two portions, which were respectively used as rough and brown rice for storage at 35±1 °C with relative humidity of 65±3% for ten months. The drying characteristics and milling quality of rice were determined. Free fatty acid, peroxide value and iodine value were determined to detect any notable degradation of lipids in rough and brown rice during storage. High heating and drying rates of rice were achieved under IR heating. It took only 58 s to heat rough rice to temperature of 60 °C with corresponding moisture removal of 2.17 percentage points during IR heating. The total moisture removal after natural cooling reached to 3.37 percentage points without additional energy input. IR drying did not show any adverse effects on milling quality of the dried rice. Additionally, it resulted in an effective inactivation of lipase and consequent improvement in the long-term storage stability of rough and brown rice was achieved under accelerated storage condition. It is concluded that the improvement in rough and brown rice stability during storage can be achieved through drying rough rice using IR heating to temperature of 60 °C followed by tempering for 4 h and natural cooling. IR drying provides a potential to store brown rice instead of rough rice with extended shelf life and reduced cost.