Comparison of Microwave and Conventional Thermal Pasteurization of Frozen Green Beans

Primary Author: ZHI QU

Faculty Sponsor: Juming Tang


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

Category: Agricultural and Natural Resource Sciences

Campus: Pullman





Pasteurization is the process to eliminate pathogens and extend shelf life of food products. Consumer’s desire for high quality food and convenience has been a major driver for advancements of processing technologies. Microwave pasteurization can provide more rapid heating and better heating uniformity compared to conventional thermal pasteurization, thus holds potential to produce better quality vegetable products, such as fresh appearance and texture. The objective of this research was to study the influence of microwave and conventional thermal pasteurization on quality of green beans during storage at various cold chain temperatures.


Thawed frozen green beans were vacuum sealed in 8 oz polymer trays, pasteurized in a pilot-scale 915 MHz Microwave Assisted Pasteurization System (MAPS) and conventional water bath (WB). The processed samples were stored at 10 and 2 °C. Color and chlorophyll content of green beans were quantified to elucidate the quality of the food.


For green beans, chlorophyll and green color suffered greater degradation when pasteurized using WB. During storage, under both temperatures, microwave pasteurized samples showed better color retention and higher chlorophyll content. And, microwave pasteurized green beans can be preserved for a longer time at 2°C (100 days) than WB heated one (80 days) with no package swelling observed. This implicates that microwave pasteurization might be a potential alternative to produce safe, high-quality vegetable products and preserve the quality during storage.