Development and Validation of Analytical Chart for 915 MHz Single-mode Microwave Assisted Thermal Processing Conditions

Primary Author: Yonas Gezahegn

Faculty Sponsor: JumingTang


Primary College/Unit: Agricultural, Human and Natural Resource Sciences

Category: Engineering and Environmental Science

Campus: Pullman




Microwave thermal processing has wide applications in the food industries such as drying, pasteurization and sterilization. In microwave heating understanding the relation between dielectric properties and processing conditions is key in accurately predicting the heating rate that ensures food safety. Hence, this research aims to develop an analytical chart that will relate the dielectric properties and processing conditions to accurately predicted the cold spot temperature in the center layer of food. By measuring some physical properties of food samples (mashed potato, rice and pea) and applying analytical equations the chart was developed using MATLAB2019a software. In predicting dielectric constant, the chart was accurate with 0 – 1.2%, 0.1 – 2.3% and 0 – 4.6% error, for the products respectively. The optimum salt content of 0.1%, 1% and 0.5% were discovered for higher heating rates, respectively. The best preheating temperatures were also determined, where higher salt content foods have a less preheating temperature for maximum heating rate. It was also possible to related dissipation power and heating rate to predict the cold spot temperature at a given microwave heating time. Using mashed potato sample 0% salt and 22 mm, 0.6% salt and 22 mm, 0.6% salt and 40 mm, 0.1% salt and 40 mm, 0% salt and 35 mm the temperature prediction error was only 0 – 2%,  0 – 3%, 0 – 6%, 0 – 9%, and 0 – 6%, respectively. In conclusion, the analytical chart accurately predicts dielectric properties and processing conditions that can save time and resources