Synergistic bactericidal effect and mechanism of X-ray irradiation and citric acid combination against food-borne pathogens on spinach leaves

• Published in: Food microbiology Vol. 91; p. 103543
• Main Authors: Jeon, Min-Jin, Ha, Jae-Won
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2020
• Subjects: Cell Membrane - drug effects; Cell Membrane - radiation effects; Citric acid; Citric Acid - pharmacology; Colony Count, Microbial; Disinfectants - pharmacology; Escherichia coli O157 - drug effects; Escherichia coli O157 - growth & development; Escherichia coli O157 - metabolism; Escherichia coli O157 - radiation effects; Food Irradiation - methods; Food Microbiology; Foodborne pathogens; Inactivation; Listeria monocytogenes - drug effects; Listeria monocytogenes - growth & development; Listeria monocytogenes - metabolism; Listeria monocytogenes - radiation effects; Mechanism; Plant Leaves - microbiology; Reactive Oxygen Species - metabolism; Spinach; Spinacia oleracea - microbiology; X-ray irradiation; X-Rays; Foodborne pathogens; Spinach; Inactivation; X-ray irradiation; Citric acid; Mechanism
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2020.103543

In this study, we investigated the antimicrobial activity of the X-ray irradiation and citric acid (CA) combination against Escherichia coli O157:H7 and Listeria monocytogenes on the surface of spinach leaves and elucidated the mechanisms underlying their synergistic interaction. Upon treatment with 0.3 kGy X-ray irradiation and 1% CA combination, the cell counts of E. coli O157:H7 and L. monocytogenes reduced by 4.23 and 3.69 log CFU/mL on spinach leaves, respectively. The synergistic reduction in the cell counts of E. coli O157:H7 and L. monocytogenes by the combination treatment was 0.95 and 1.14 log units, respectively. The X-ray and CA combination exerts its antimicrobial effect by damaging the bacterial cell membrane and enhancing the generation of intracellular reactive oxygen species in the pathogens. The enhanced bactericidal effect of the combination treatment may not be due to the loss of intracellular enzyme activity. We also evaluated the effect of the combination treatment on the quality attributes of spinach leaves. The combination treatment did not result in adverse changes in color and texture of spinach leaves. These results demonstrate the potential of citric acid and X-ray irradiation combination for decontaminating foodborne pathogens on fresh produce. •X-ray and citric acid combination showed a synergistic bactericidal effect against two major pathogens on spinach leaves.•Cell membrane damage and ROS generation were the main bactericidal mechanism.•The combined treatment did not result in adverse changes in quality of spinach.