Effectiveness of Washing Procedures in Reducing Salmonella enterica and Listeria monocytogenes on a Raw Leafy Green Vegetable (Eruca vesicaria)

Abstract

Vegetables are an important source of nutrients, but they can host a large microbial population, particularly bacteria. Foodborne pathogens can contaminate raw vegetables at any stage of their production process with a potential for human infection. Appropriate washing can mitigate the risk of foodborne illness consequent to vegetable consumption by reducing pathogen levels, but few data are available to assess the efficacy of different practices. In the present work, six different washing methods, in the presence or absence of sanitisers (peracetic acid and percitric acid, sodium bicarbonate, sodium hypochlorite) and vinegar, were tested for their effectiveness in reducing Salmonella and Listeria counts after artificial contamination of raw rocket (Eruca vesicaria). Results showed that washing with sodium hypochlorite (200 mg/L) was the only method able to produce a significant 2 Log reduction of Salmonella counts, but only in the case of high initial contamination (7 Log CFU/g), suggesting potential harmful effects for consumers could occur. In the case of Listeria monocytogenes, all the examined washing methods were effective, with 200 mg/L sodium hypochlorite solution and a solution of peracetic and percitric acids displaying the best performances (2 and 1.5 Log reductions, respectively). This highlights the importance of targeting consumers on fit for purpose and safe washing practices to circumvent vegetable contamination by foodborne pathogens.

Transmission of pathogens within the commonly consumed vegetables: Bangladesh perspective

“…A healthy human diet requires a considerable intake of vegetables due to the obvious benefits it can posses; many developed countries have advocated the daily consumption of substantial amounts of fruits and vegetables as a necessity for maintaining good health (1)(2)(3).Vegetables are known to be the most important basis of nutrients, dietary fiber, vitamins and minerals (4). A side from the health benefits, ironically, the increased consumption of fruits and vegetables has contributed to lowering the risk of various chronic diseases including enteric diseases, cardiovascular diseases and even of the onset of cancer (5-10).…”

“…Contamination with both microorganisms such as Listeria monocytogenes, Salmonella enterica, and o Received 10 September 2018/Accepted 10 October 2018 Escherichia coli O157:H7 and chemicals are a long term concern in food safety resulting in disease outbreaks (4,(11)(12)(13)(14). Vegetables, particularly raw vegetables, have previously been identified as a vehicle for the transmission of various bacterial, viral and parasitic pathogens (3).…”

The Hurdle Approach–A Holistic Concept for Controlling Food Safety Risks Associated With Pathogenic Bacterial Contamination of Leafy Green Vegetables. A Review

“…These treatments have led to reductions in pathogens, but none of the methods has proven sufficient to eliminate the pathogenic bacterial load completely. A number of studies have investigated the effect on foodborne pathogens of addition of chlorine to the wash water (Behrsing et al, 2000; Beuchat et al, 2004; Gragg and Brashears, 2010; Davidson et al, 2013; Omac et al, 2015; Pezzuto et al, 2016; Guzel et al, 2017). The efficacy of hypochlorite treatment is dependent on the microbial load of the inoculated pathogen and the target organism (Pezzuto et al (2016).…”

“…A number of studies have investigated the effect on foodborne pathogens of addition of chlorine to the wash water (Behrsing et al, 2000; Beuchat et al, 2004; Gragg and Brashears, 2010; Davidson et al, 2013; Omac et al, 2015; Pezzuto et al, 2016; Guzel et al, 2017). The efficacy of hypochlorite treatment is dependent on the microbial load of the inoculated pathogen and the target organism (Pezzuto et al (2016). Listeria monocytogenes and L. innocua (used as a surrogate for L. monocytogenes ) have been shown to resist treatment even when hypochlorite is administered in high concentrations, but this treatment is still more successful than washing without an additive (Beuchat et al, 2004; Omac et al, 2015; Guzel et al, 2017).…”

“…For example, peroxyacetic acid has been used against E. coli O157:H7 and L. monocytogenes (Baert et al, 2009) and peracetic acid, percitric acid, sodium bicarbonate and vinegar have been used against Salmonella and Listeria (Pezzuto et al, 2016). Edible plant extract, such as the pulp and juice of lime fruits and oregano, has been used against Salmonella, E. coli O157:H7 and Shigella sonnei (Orue et al, 2013).…”