Development of Microwave Heating Method for Rice Drying Deandrae Smith Dr. Griffiths G. Atungulu Statement of research problem Approach Objective Methods Results Conclusion Conventional drying of grain is done using: Convective heated air Natural air, in bin drying In both approaches inter kernel MC and temperature gradients exist during drying The inter kernel MC and temperature gradients Induces swelling or contraction within endosperm May result in differences in tensile properties across the kernel Fissures or cracks result from swelling or contraction Stresses. Fissures reduce rice kernel s ability to withstand the processes of hulling and bran removal without breaking apart Ultimate Problem Reduced Head Rice Yield
Part of the electromagnetic spectrum Lies between infrared and radio waves I. Volumetric heating Reduced inter kernel MC and temp. gradients Reduced fissuring Improved head rice yield The individual water molecules within the product rotate to align their dipoles with respect to the changing electric field they are subjected to thus generating heat. II. One pass, rapid rice drying a. Conventional Heating at surface b. Microwave Volumetric Heating III. Inactivate harmful microbes such as mold that leads to. Aflatoxin contamination Mycotoxin produced by Aspergillus molds Very toxic and highly carcinogenic Treatments on infected peanuts and yellow corn proven effective at microbe inactivation. To investigate the effectiveness of a microwave to achieve one pass rice drying that: Reduces MC and temperature gradients within individual rice kernels during drying Prevents fissuring of rice kernels to maintain rice milling quality.
. Freshly harvested, MG rice Cultivar: Jupiter Initial MC:.% (wb). Industrial Microwave Rice Cleaning MW Treatments With/Without Tempering Using Forced Air Cooling Moisture Content Readings Gravimetric Machine read Oven Method Milling and HRY Calculations The full system consists of: Transmitter Lab Oven Wave Guide Lab Oven Transmitter Wave Guide Industrial Microwave Power: 7 kw Frequency: 0.9 GHz Wavelength:.8 cm Household Microwave Power:. kw Frequency:. GHz Wavelength:. cm Desired Power Output (kw) Cavity Dwell Time (mins) Start/Stop Microwave Desired belt Speed (in/min)
Method Power (kw) Time (mins) 0 0. 0 Microwave (Natural Cooling) 0 0. 0 Microwave w/ Tempering (Natural Cooling) 0 0. 0 Microwave w/ Forced Air Cooling Methods x 8 treatments x replicates = 7 Experiments Kicker Laboratory Grain Cleaner: Series of small sized sieves Used to remove dockage. Bed Depth: 0.0 m Procedure. Equilibrate with room temperature ( o C).. kg of rice placed into microwave safe trays. Rice treatment. Cooled in EMC chamber. MC readings 6. Weighed Additional steps:. Sealed in glass jars with a HOBO sensor. Environmental test chamber (60 o C, % RH) 6. Cooled in EMC chamber 7. MC reading 8. Weighed A forced air cooling apparatus was constructed using:. A plastic cooling tray w microfiber mesh. blower Additional Steps. Cooled in EMC chamber. MC Reading 6. Weighed
Gravimetric moisture content was calculated. Moisture content was verified using:.am 00 MC Reader.Oven Moisture Content (ASABE standard) AM 00 Grain Moisture Tester 9 MHz radio waves Measures moisture content Procedure. Cooled to room temperature. MC was measured times. Average was recorded Before calculating the Head Rice Yield the rice was sorted to remove;. Kernels that were not hulled properly. Kernels that were less than / of a whole kernel. Chalky, striated, yellowish or greenish grains, and other foreign material. Results 0 Initial Temp: 7. o C 0 kw kw 0 kw kw kw MP0T. M: Refers to the mass in kg P: Refers to the Power in kw T: Refers to the time treated in minutes Rice was treated at 0,, 0, and kw for.,,, and minutes. 0 Rice Surface Temperature (deg. C) 0 00 80 60 0 0 0 0. Time (mins)
80 Theoretical Milling Yield: ~70% Moisture Content (%) 6.%.% Power 0 0 0 Time 0..%.6% Milled Rice Yield (%) 70 60 0.6%.% 0 Control 8 0 0 0 Energy (kwmin) Increasing Energy 60.% 8.7%.8% Head Rice Yield(%) Power 0 0 0 Time 0. 9.6% Energy (kwmin) 0 8 0 0.8%.% 70.% 6.8% 70.% 6.8% Microwave with Tempering Power Time (min) MC Reduction (ppt) MC Final (%) HRY(%) (kw) 9.. 6.8 7.9.6 70. Future plans include optimizing tempering times so as to not waste time and energy. Conduct experiments on long grain rice. Determine any changes in: o viscous properties of the rice starch o assess reduction in microbial activity/mold activity o Assess change in the flavor profiles of treated rice Acknowledgements Advisor: Dr. Griffiths G. Atungulu Research Group Shantae Wilson Supriya Thote Hou Min Zhong Zachary Young Anne Okeyo Arnelia Couch 6
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