Inactivation of foodborne pathogens influenced by dielectric properties, relevant to sugar contents, in chili sauce by 915 MHz microwaves

The objective of this study was to investigate the effect of sugar content on dielectric properties of chili sauce, and inactivation efficiency when exposed to microwave energy. Heating history showed sugar content was an important factor influencing heating rate when chili sauce was exposed to microwave energy. Also, chili sauce of lower sugar content had a higher dielectric constant and dielectric loss factor. This trend was linked to inactivation efficiency of chili sauce inoculated with foodborne pathogens. As sugar content decreased, the time required to inactivate foodborne pathogen was reduced. Also, the inactivation efficiency of microwave heating was better since conventional heating took much longer to inactivate foodborne pathogens to under the detection limit. Also, our results showed that there was no significant difference in color, except for 25% and 40% sugar content exposed to 915 MHz microwave at 3.0 kW. Even though decreased water activity was observed, there was no significant difference between conventional heating and microwave heating at 1.5 kW and 3.0 kW. These results show not only that microwave heating can inactivate foodborne pathogens without generating significant quality change but also that the effect relies on dielectric properties associated with the sugar content of chili sauce.