Comparison of the effectiveness of acidified sodium chlorite and sodium hypochlorite in reducing Escherichia coli

Possible sources of Listeria monocytogenes contamination of fresh-cut apples and antimicrobial interventions during antibrowning treatments: a review

Fresh-cut apples, being rich in antioxidants and other nutrients, have emerged as popular snacks in restaurants, at home and in school lunch programs, partially due to freshness, convenience, and portion size availability. Two major challenges in processing fresh-cut apples are browning of cut surfaces and contamination with human pathogens. Regarding human pathogens, contamination by Listeria monocytogenes is a major concern, as evidenced by two recent outbreaks of whole apples and numerous recalls of fresh-cut apples. Antibrowning agents currently used by the industry have little to no antimicrobial properties. The present review discusses possible origins of L. monocytogenes in fresh-cut apples, including contaminated whole apples, and contamination via the processing environment and the equipment in fresh-cut facilities. Treatment with antibrowning solutions could be an opportunity for Listeria contamination and represents the last chance to inactivate pathogens. The discussion is focused on the antibrowning treatments where formulations and coatings with antibrowning and antimicrobial properties have been developed and evaluated against Listeria and other microorganisms. In addition, several research needs and considerations are discussed to further reduce the chance of pathogen contamination on fresh-cut apples.

The antibacterial mechanism of ultrasound in combination with sodium hypochlorite in the control of Escherichia coli

In the present study, the action mechanism of ultrasound (US) combined with sodium hypochlorite (SH) against Escherichia coli was illustrated by different analysis, including reduction, particle size distribution, scanning electron microscopy (SEM), transmission electron microscopy (TEM), K⁺ leakage, confocal laser scanning microscopy (CLSM) and fluorescence spectroscopy of Escherichia coli. The results showed that ultrasound improved the antimicrobial effect of SH in control of E. coli. No significant difference was obtained in reduction of E. coli, CLSM analysis and K⁺ leakage between US + SH₃₀ (US + 30 ppm SH) and SH₅₀ (50 ppm SH) treatment. Smaller particle size was recorded in US and US + SH₃₀ treatment. The changes of morphology and intracellular organization of E. coli cells as a result of these treatments were confirmed by SEM and TEM analyses. Fluorescence spectroscopy results indicated SH₃₀, US + SH₃₀ and SH₅₀ treatment caused the burial of tyrosine residues and tryptophan residues as well as increase of hydrophobicity. Therefore, the mechanism of US + SH₃₀ treatment against E. coli involved decreased particle size, damaged membrane and changes of intracellular organization and protein conformation.

Inactivation of Salmonella on Sprouting Seeds Using a Spontaneous Carvacrol Nanoemulsion Acidified with Organic Acids

Over the past decade, demand has increased for natural, minimally processed produce, including sprout-based products. Sanitization with 20,000 ppm of calcium hypochlorite is currently recommended for all sprouting seeds before germination to limit sprout-related foodborne outbreaks. A potentially promising disinfectant as an alternative to calcium hypochlorite is acidified spontaneous essential oil nanoemulsions. In this study, the efficacy of an acidified carvacrol nanoemulsion was tested against mung beans and broccoli seeds artificially contaminated with a Salmonella enterica Enteritidis cocktail (ATCC BAA-709, ATCC BAA-711, and ATCC BAA-1045). Treatments were performed by soaking inoculated seeds in acidified (50 mM acetic or levulinic acid) carvacrol nanoemulsions (4,000 or 8,000 ppm) for 30 or 60 min. After treatment, the number of surviving cells was determined via plate counts and/or the most probable number (MPN) approach. Treatment for 30 min successfully reduced Salmonella Enteritidis by 4 log CFU/g on mung beans (from an initial contamination level of 4.2 to 4.6 log CFU/g) and by 2 log CFU/g on broccoli seeds (from an initial contamination level of 2.4 to 2.6 log CFU/g) to below our detection limit (≤3 MPN/g). Treated seeds were sprouted and tested for the presence of pathogens and sprout yield. The final sprout product had no detectable pathogens, and total sprout yield was not influenced by any treatment.