HEATING UNIFORMITY STUDY IN LOW MOISTURE SEMI-SOLID FOOD SUBJECTED TO RADIO FREQUENCY HEATING

摘要

Radio frequency (RF) heating has a fast and volumetric heating characteristic, which may fulfill the needs of pasteurization on low moisture food due to the high heat resistance of food pathogen in low moisture environment. To provide adequate information for pasteurizing paste using RF energy, peanut butter was selected and conditioned to 5 moisture content levels (1.3%, 4%, 10%, 16%, 22% w.b.). Physical, thermal and dielectric properties were measured at 20-80 °C and 1-1800 MHz. The heating uniformity test was conducted on a lab scale 27.12 MHz, 6 kW RF heating system, and water surrounding was found to be the most efficient way in improving heating uniformity. A mathematical model was built up for guiding the experiment, and the cold spot location and heating rate were verified accordingly.