Electrostatic Sprays of Food‐Grade Acids and Plant Extracts are More Effective than Conventional Sprays in Decontaminating Salmonella Typhimurium on Spinach

Abstract

About 40000 people fall victim to Salmonella infections every year in the United States. Recent occurrences of Salmonella contaminated spinach and its recalls have accelerated the need for efficient antimicrobials targeting these pathogens. Our study was aimed at evaluating the inhibitory properties of malic, tartaric, and lactic acids, and grape seed extract (GSE) alone and in combinations and their application methods against Salmonella Typhimurium-inoculated spinach using a response surface method. Fresh spinach leaves were washed, disinfected with sodium hypochlorite solution (0.04% v/v), rewashed with sterile deionized (DI) water, and inoculated with a 2nd-day culture of S. Typhimurium (7.0 log CFU/mL). Adhered S. Typhimurium population on day 0 were 7.5 log CFU/g. These were treated with individual and combinations of organic acids with GSE or DI water (control) adjusted to the same pH as that of the test solutions with both the modes of application and leaves were refrigerated at 4 °C. Malic acid (2%) in combination with GSE (3%) or lactic acid (3%) sprayed electrostatically showed reductions of 2.6 to 3.3 log CFU/g compared to lower log reductions (0.0 to 0.3 log CFU/g) by day 14 if sprayed conventionally. These findings indicate that malic acid in combination with GSE/lactic acid solutions applied by electrostatic spraying exhibited higher inhibition of pathogens than conventional spraying and can be used for commercial applications to enhance food safety.

Comparison of multiple chemical sanitizers for reducing Salmonella and Escherichia coli O157:H7 on spinach (Spinacia oleracea) leaves

“…Similarly, Lin et al (2002) obtained a 4 log CFU/g reduction of Salmonella Enteritidis on lettuce with application of 1.5% lactic acid at room temperature, but severe browning of the lettuce occurred with this treatment. Ganesh et al (2010) also found that 2% lactic acid when sprayed on inoculated spinach leaves reduced S. Typhimurium by approximately 1.5 log CFU/g during refrigerated storage as compared to the control.…”

Systematic Screening of Plant Extracts from the Brazilian Pantanal with Antimicrobial Activity against Bacteria with Cariogenic Relevance

“…Among the six compounds identified, the literature has already demonstrated the antimicrobial activity of three of them (malic acid, scopoletin and ferulic acid) [Craveiro and Silveira, 1982;Ganesh et al, 2010;Borges et al, 2012]. The antimicrobial activity of the three other compounds has yet to be uncovered.…”

Green tea and grape seed extracts — Potential applications in food safety and quality

“…Electrostatic spray application demonstrated successful results in reducing foodborne pathogens on various food applications such as chicken carcasses, eggs, and bananas (Kim et al, 2005;Law & Cooper, 2001;Russell, 2003a,b). Ganesh et al (2010) reported that electrostatic spraying (in comparison to conventional treatments) of spinach with malic acid (MA) and GSE yielded 2.6 and 3.3 log reductions of L. monocytogenes and Salmonella Typhimurium (S.T) on days 7 and 14 respectively compared to the reductions by control (0.1 and 0.0 log CFU/g) ( Table 3). Combination of an electrostatic spray of 2% tartaric acid and 2% GSE, and a spray of 2% MA and 2% GSE led to more reductions in bacterial log numbers: 3.3 to 3.6 log CFU/g and 1.5 to 3.8 logs CFU/g respectively (Ganesh et al, 2010).…”

“…Ganesh et al (2010) reported that electrostatic spraying (in comparison to conventional treatments) of spinach with malic acid (MA) and GSE yielded 2.6 and 3.3 log reductions of L. monocytogenes and Salmonella Typhimurium (S.T) on days 7 and 14 respectively compared to the reductions by control (0.1 and 0.0 log CFU/g) ( Table 3). Combination of an electrostatic spray of 2% tartaric acid and 2% GSE, and a spray of 2% MA and 2% GSE led to more reductions in bacterial log numbers: 3.3 to 3.6 log CFU/g and 1.5 to 3.8 logs CFU/g respectively (Ganesh et al, 2010). An advantage of electrostatic spraying over conventional spraying is that electrostatic spraying can cause a consistently even and retained surface coverage with the applied antimicrobial.…”

“…In addition, delivering these vital components through advanced technologies such as electrostatic spray and nanoscale delivery into food systems may provide promising results and require extensive investigation to use these cheap, natural and safe plant extracts (Ganesh et al, 2010;Ravichandran, Hettiarachchy, Johnson, Ricke, Slavik et al, 2010).…”