Combination effect of 915 MHz microwave heating and carvacrol for inactivation of Escherichia coli O157:H7, Salmonella Typhimurium and Listeria monocytogenes in hot chili sauce

Hot chili sauce is a type of condiment whose popularity is steadily increasing with the incline of a risk for foodborne outbreaks. The combination effect of 915 MHz microwave and carvacrol was studied to inactivate the foodborne pathogens inoculated in hot chili sauce. The addition of 3.25 mM carvacrol did not change the dielectric properties including dielectric constant and dielectric loss factor, which remained at 54.1 and 80.5, respectively. Also, the heating rate was not influenced by the addition of carvacrol (p > 0.05). Time to reach 100 °C was 65 s for both samples with or without carvacrol. However, adding 3.23 mM carvacrol generated a synergistic effect against E. coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes when combined with 915 MHz microwave. An additional population reduction of 1.0–2.6 log CFU/ml for the different pathogens was observed under the combined treatment of 40 s. No significant amounts of injured cells were observed. Furthermore, combination treatment did not result in a significant change in the color or water activity of hot chili sauce. No significant difference in volatile compound contents was found. This study demonstrates the potential of combining carvacrol and 915 MHz microwave for sauce processing without significant quality changes.