ARS | Publication request: Efficacy of plant essential oils in reducing E. coli O157:H7 and Salmonella on spinach leaves

Submitted to: Annual Meeting of the Institute of Food Technologists
Publication Type: Abstract Only
Publication Acceptance Date: February 10, 2011
Publication Date: June 11, 2011
Citation: Yossa, N., Patel, J.R., Millner, P.D., Lo, M. 2011. Efficacy of plant essential oils in reducing E. coli O157:H7 and Salmonella on spinach leaves[abstract]. Annual Meeting of the Institute of Food Technologists. Book of abstracts #199-09.

Technical Abstract: Foodborne outbreaks associated with consumption of fresh produce have increased in recent years. Chlorine is widely used as a produce wash to control pathogens on fresh produce; however, it is less effective in presence of organic matter. The efficacy of cinnamaldehyde and sporan alone, or in combination with acetic acid in reducing E. coli O157:H7 and Salmonella on spinach leaves was investigated. Spinach leaves were inoculated with a cocktail of five-strain Salmonella or E. coli O157:H7 (5 log cfu/g), air-dried for 30 min, and then immersed in a treatment solution containing cinnamaldehyde or Sporan (600, 800, and 1000 ppm) alone, or in combination with 200 ppm acetic acid (20%) for 1 min. Treated leaves were spin-dried and analyzed after washing, and during 14-days storage at 4°C. Inoculated leaves washed with water were used as control. The samples were plated in XLT4 and SMAC for Salmonella and E. coli O157:H7 populations. Un-inoculated leaves immersed in treatment solutions were used for color and texture analysis. Treatment with 800 ppm cinnamaldehyde or 1000 ppm sporan significantly reduced E. coli O157:H7 and Salmonella from spinach leaves. Combination of acetic acid with cinnamaldehyde or sporan further reduced these pathogens on spinach leaves; however, the effect of acetic acid was not significant. E. coli O157:H7 was more sensitive to cinnamaldehyde treatment compared to Salmonella. Bacterial population decreased significantly during storage. Color and texture characteristics of sporan-treated leaves after 14 days were not significantly different from control-treated spinach leaves. Results indicate that these natural oils could be used to reduce E. coli O157:H7 and Salmonella on organic spinach without affecting the sensory quality.