Combined effect of ultrasound and organic acids to reduce Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes on organic fresh lettuce

Abstract

This study was performed to compare the effectiveness of individual treatments (ultrasound and organic acids) and their combination on reducing foodborne pathogens on organic fresh lettuce. Lettuce leaves were inoculated with a cocktail of three strains each of Escherichia coli O157:H7, Salmonella Typhimurium, and Listeria monocytogenes and treated with ultrasound (40 kHz) alone, organic acids (0.3, 0.5, 0.7, 1.0, and 2.0%--malic acid, lactic acid, and citric acid) alone and combined with ultrasound and organic acids for 5 min. For all 3 pathogens, the combined treatment of ultrasound and organic acids resulted in additional 0.8 to 1.0 log reduction compared to individual treatments, without causing significant quality change (color and texture) on lettuce during 7 day storage. The maximum reductions of E. coli O157:H7, S. Typhimurium, and L. monocytogenes were 2.75, 3.18, and 2.87 log CFU/g observed after combined treatment with ultrasound and 2% organic acid for 5 min, respectively. Our results suggest that the combined treatment of ultrasound with organic acids was effective at increasing pathogen reduction compared to individual treatments without significantly affecting quality, and demonstrates its potential as a novel method to increase the microbial safety on organic fresh lettuce.

Microbial Decontamination of Fresh Produce (Strawberry) Using Washing Solutions

“…Studies showed that combination of vinegar and lemon juice (1:1) reduced the log counts of 6.0 to 5.7 of viable S. Typhimurium and reduced to undetectable level when treatment was applied up to 30 min (Sengun & Karapinar, 2004). Similarly, other studies found that combination of 2% organic acids (malic, lactic and citric acids) and ultrasound of 40 kHz reduced number of E. coli O157:H7, L. monocytogenes and S. Typhimurium on lettuce leaves by 3.2-2.3 Log CFU/g (Sagong et al, 2011). In another study, combination of alkaline electrolyte water and 1% acetic acid reduced L. monocytogenes and E. coli O157:H7 by 4 Log CFU/g on shredded carrots (Rahman at al., 2011).…”

Effects of ascorbic acid, citric acid, lactic acid, NaCl, potassium sorbate and Thymus vulgaris extract on Staphylococcus aureus and Escherichia coli

“…Other studies reported that citric acid (2%) was more effective against gram-positive bacteria (Bacillus cereus, and S. aureus) than gram-negative bacteria (Salmonella enteritidis, and E. coli) (del Rio et al, 2007). Also, increasing concentration of citric acid may reduce the growth of E. coli (Sagong et al, 2011). Lactic acid (0.03% or 0.1%) nearly completely inhibited the growth of S. aureus or E. coli strains, respectively.…”

“…Kolsarici and Candogan (1995) reported that number of total psychrotrophic aerobic bacteria, staphylococci and coliform bacteria on chicken was decreased after treatment with lactic acid and storage at 4±1°C. Sagong et al (2011) observed that immersion of lettuce leaves in 0.5% lactic acid significantly reduced growth of E. coli O157: H7. Also, lactic acid (0.03 and 0.1%) lowers the pH of the medium to 3.88 and 3.32, respectively; and S. aureus and E. coli are not able to grow at this pH.…”

Evaluation of SICON ® surfaces for biofouling mitigation in critical process areas

“…Escherichia coli is one of the most persistent foodborne microorganisms (Dourou et al, 2011;Sagong et al, 2011;Shi and Zhu, 2009) and its presence on food-contact surfaces has been associated with its ability to attach and form biofilms on these surfaces (Dourou et al, 2011). The most widely used method to detect the presence of the biological contaminants on the equipment surfaces is by swabbing and bacterial cultivation in order to determine the number of cells per cm 2 (Sudheesh et al, 2013).…”