Comparison of Microwave-Assisted Thermal Pasteurization and High Pressure Processing as Pasteurization Methods for Green Beans


Faculty Sponsor: JumingTang


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

Category: Agricultural and Natural Resource Sciences

Campus: Pullman




There has been an increasing consumer desire for high quality minimally processed food. The food industry is seeking new processing technologies to meet such consumer desire by producing ready-to-eat meals (RTE) with adequate shelf-life. Novel methods such as high pressure processing (HPP) and microwave-assisted pasteurization system (MAPS) can be the good candidates for food industry. The aim is to provide scientific support to food industry about both pasteurization methods.

Based on literature review, the mild pasteurization conditions were selected as 70°C-2 min for MAPS and 600 MPa-10 min at 25°C for HHP, respectively.  For the severe pasteurization, 90°C-10 min was selected for MAPS and 600 MPa-20 min at initial temperature of 45°C were selected for HPP. The quality attributes such as color, chlorophyll content, texture, and pH of green beans were determined at 2°C over 36 days and 10°C over 20 days and at 2°C over 14 weeks and 7°C over 7 weeks for mild and severe pasteurization, respectively.

Similar color change after both pasteurization methods shows that the processing temperature of MAPS did not negatively affect the color of green beans. Severe pasteurization conditions of MAPS and HPP resulted in more loss in green color. The severe MAPS conditions resulted in less retention of firmness in comparison with the severe HPP pasteurization. This can be attributed to the higher processing temperature (90°C), which results in β-eliminative depolymerization of pectin (softening). Microbial growth, mainly acid-producing microorganisms, might be attributed to the decrease in pH and undesirable appearance and smell.