Location: Healthy Processed Foods ResearchTitle: Effect of infrared and conventional drying methods on physicochemical characteristics of stored white rice Author
|Ding, Chao - University Of California|
|Khir, Ragab - University Of California|
|Tu, Kang - Nanjing Agricultural University|
|El-mashad, Hamed - University Of California|
Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/30/2015
Publication Date: 9/15/2015
Citation: Ding, C., Khir, R., Pan, Z., Tu, K., El-Mashad, H. 2015. Effect of infrared and conventional drying methods on physicochemical characteristics of stored white rice. Cereal Chemistry. 92(5):441-448.
Interpretive Summary: The objective of this study was to investigate the effect of infrared (IR) drying followed by tempering and natural cooling on the change of physicochemical characteristics of white rice during up to 10 months of storage. High drying efficiency and good rice quality were obtained with infrared drying (IRD) of rough rice. IRD could anneal the starch at the surface layer of rice kernels, and slightly decrease the temperature and enthalpy of gelatinization and the viscosity of rice flour, which reduced the changes in rice microstructure during storage and better maintained the cooking quality of stored white rice. There was no significant difference in the hardness of cooked rice dried with different methods. Therefore, IRD is recommended to improve the drying efficiency and maintain the stability of physicochemical characteristics of white rice during storage.
Technical Abstract: The objective of this study was to investigate the effect of infrared (IR) drying followed by tempering and natural cooling on the change of physicochemical characteristics of white rice during up to 10 months of storage. The physicochemical characteristics of IR dried rice was also compared with that of conventionally dried rice. It took only 58 s to heat the rough rice from room temperature to 60 °C using IR and 2.17 percentage points of moisture was removed. After 4 months of storage, the increments of yellowness index, water uptake and volume expansion ratio of the rice dried with IR were 73.8%, 63.9% and 55.3% of that dried with ambient air drying methods, respectively. Due to the high drying temperature, IR heating could denature protein and anneal starch that located at rice surface layer, slightly decreased the gelatinization temperature, enthalpy and viscosity, reduced the changes in microstructure and maintained cooking characteristics during storage. IR drying process is recommended to maintain the quality of milled rice during storage.