|Gabel, Michael - UC DAVIS, DAVIS, CA|
|Amaratunga, K.S.P. - UC DAVIS, DAVIS, CA|
|Harris, Linda - UC DAVIS, DAVIS, CA|
|Thompson, James - UC DAVIS, DAVIS, CA|
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2006
Publication Date: October 1, 2006
Citation: Gabel, M., Pan, Z., Amaratunga, K., Harris, L.J., Thompson, J.H. 2006. Catalytic infrared dehydration of onions. Journal of Food Science. V71(9):E351-E357. Interpretive Summary: Infrared radiation as an energy efficient heating method was studied for drying onions. The drying rates and qualities of sliced onions were measured and compared under both infrared drying and hot air drying. Infrared drying showed a significant higher drying rate than hot air and is recommended to be used in the early stage of onion drying.
Technical Abstract: Dehydrated onions are commonly dried with convection heating which is inefficient and costly. This study compared the drying and quality characteristics of onion dried with catalytic infrared (CIR) heating and forced air convection (FAC) heating. Sliced high solids onions were dehydrated under nine conditions: CIR heating with and without air recirculation, and FAC, each operated at 60, 70 and 80°C. In general, CIR both with and without air recirculation had higher maximum drying rates, shorter drying times and greater drying constants than FAC. Dried onion quality, measured as pungency degradation, was similar for both the drying methods at 60°C and 70°C. The color analysis showed better product color (whiter and less yellow) at lower temperatures for CIR and higher temperatures for FAC. The browning could have been caused by the higher heat intensities of the CIR heating and longer process times of FAC drying. Aerobic plate counts and coliform counts were not significantly different for either product from the CIR or FAC drying. However, samples dried by the CIR had significantly lower yeast and mold counts than those dried by the FAC. It is recommended that CIR be used in the early stages of onion drying.