Electrostatic Spraying of Passion Fruit (Passiflora edulis L.) Peel Extract for Inactivation of Escherichia coli O157:H7 and Listeria monocytogenes on Fresh-Cut Lollo Rossa and Beetroot Leaves

Abstract

In the present study, we evaluated the antimicrobial activity of passion fruit peel extract (PPE) against Escherichia coli O157:H7 and Listeria monocytogenes. The application of PPE using an electrostatic spraying system for the disinfection of fresh-cut Lollo Rossa and beetroot leaves was also examined and compared with conventional PPE washing. Time-kill assays indicated that PPE had antibacterial activity against Escherichia coli O157:H7 and Listeria monocytogenes, effectively reducing the populations of the pathogenic bacteria within 3 h following treatment with 6 mg/mL PPE. Confocal laser scanning microscopy and scanning electron microscopy showed that PPE treatment caused bacterial cell death by damaging the cell membrane. PPE treatment produced significant decontamination against the pathogens on fresh-cut vegetables. Electrostatic spraying of 6 mg/mL PPE for 20 s decreased the populations of pathogenic bacteria on Lollo Rossa and beetroot leaves by 2.29–2.86 log CFU/g, regardless of the difference in the contact angle and surface roughness of the vegetables. Our results showed that electrostatic spraying of PPE was more effective than washing with PPE. Electrostatic spraying of PPE did not affect the color and texture of fresh-cut Lollo Rossa leaves during storage, suggesting that it can be used as a novel disinfection method.