Radio Frequency Heating Behaviors Of Pizza With Multi-components

Radio frequency(RF)heating is a new potential treatment technology between 3 k Hz and 300 MHz.It can quickly raise the overall temperature of the material,has a large penetration depth,possesses high energy efficiency,and meets safe production requirements.Therefore,it is widely used in food and agricultural products processing for disinfestation,pasteurization,enzyme inactivation,drying,baking,thawing and other applications.RF heating technology has been studied for many years and great progress has been made in RF heating behaviors,heating uniformity,mechanism analysis,and application.However,most of the researches are based on the same food or agricultural product,which is usually considered as a uniform or homogeneous material.However,the research on multi-component foods and agricultural products with large differences in RF heating behaviors is very limited.Based on this special problem,this study selected a representative pizza as the multi-component material,containing base,cheese,salami,and onion,and applied the finite element simulation method to build a RF heating model,and analyzed the heating behaviors of RF treatments of multicomponent pizza,and finally compared the heating behaviors among RF,microwave and traditional heating methods.The main contents and results of the study are as follows:(1)Physical properties of four pizza components were determined,including density,thermal conductivity,specific heat capacity,and dielectric properties.The results showed that the temperature had a small effect on the density,thermal conductivity,and specific heat capacity of each pizza component,but a large effect on the dielectric properties.The dielectric properties of components increased with increasing temperature and decreasing frequency.These data provided a solid basis for developing the finite element simulation model of RFheated pizza.(2)A finite element simulation model was established to obtain RF heating behaviors of pizza components,such as electric field distribution,heating rate,and temperature distribution.A 27.12 MHz,6 k W RF heating system was used to heat the pizza and verify the simulation results.Both simulation and experimental results showed that during the RF heating of multicomponent pizza,the maximum temperature difference between different components reached 29 ° C,‘edges effect' appeared,and the components with higher loss factor did not result in higher heating rate.(3)The heating performances(heating rate,surface temperature distribution and product quality)of pizza were compared among RF,microwave,and traditional heating methods.The results showed that it took 5.75,4.16,and 9.67 min to heat the pizza to 85 ? with RF,microwave,and electric oven,respectively.The heating uniformity indexes were 0.158?0.214 and 0.104,respectively,for RF,microwave,and electric oven.The heating uniformity became worse is from electric oven to RF,and microwave.The effect of RF heating on color of base,cheese and salami was greater than that of microwave and oven,and the effect of RF heating on onion color was similar to that of oven,but less than that of microwave;three heating methods had different effects on the texture of different components of pizza.