Implications of Microwave Drying Using 915 MHz Frequency on Rice Physiochemical Properties

Abstract. The objective of this study was to investigate the effects of utilizing an industrial MW to rapidly dry high moisture content (MC) rice on the physiochemical properties. Medium-grain rough rice (cv. CL721) at initial MC of 24% (w.b.) was dried using a 915 MHz industrial MW set to transmit energy at power levels 5, 10, and 15 kW for 4, 6, and 8 minutes and rice bed thicknesses 5, 10 and 15 cm. Near-infrared (NIR) spectroscopy and a rapid visco-analyzer (RVA) were used to assess the milled rice protein content, surface lipid content (SLC), total color difference (TCD) and rice peak and final viscosities (cP). The effect of increasing MW specific energy was statistically significant for all of the responses studied. Increasing MW specific energy resulted in an increase in measures rice surface lipid content (SLC), protein content and final and peak viscosities. Responses increased to a maximum then decreased at specific energies over 800 kJ/kg-grain. The opposite profile was true for rice total color difference. TCD decreased as a result of increasing MW specific energy to a trough at 533.33 kJ/kg-grain then increased at specific energies over 600 kJ/kg-grain. The effect of varying rice bed thicknesses was not statistically significant.