IMPROVED SANITIZING TREATMENTS FOR FRESH TOMATOES

Authors: Sapers, Gerald; Jones, Donyel

Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/10/2006
Publication Date: 7/15/2006
Citation: Sapers, G.M., Jones, D.M. 2006. Improved sanitizing treatments for fresh tomatoes. Journal of Food Science. 71(7):M252-M256.

Interpretive Summary: Although fresh tomatoes have repeatedly been associated with major outbreaks of food poisoning caused by human pathogens, efforts to disinfect them with chlorine or other sanitizing agents have had only mixed success. Our objective was to determine whether hydrogen peroxide treatments would be more efficacious than conventional methods in disinfecting contaminated tomatoes, and at the same time, be non-injurious to tomato quality. To simulate preharvest contamination, tomatoes were inoculated with a non-pathogenic strain of Escherichia coli or a combination of two strains of Salmonella, associated with previous tomato outbreaks, and then held for 0, 24 or 48 hours at 24 C. After storage the tomatoes were treated with a water rinse, 200 ppm chlorine solution, 1 or 5% hydrogen peroxide solutions at 20 or 60 C, or water at 60 C, and the number of surviving target bacteria was determined. The chlorine treatment, hot water and 1% hydrogen peroxide were only marginally more effective than an equivalent water rinse in reducing these bacterial populations on tomatoes stored for 24 or 48 hours. Application of 5% hydrogen peroxide at 60 C resulted in a 99% reduction, but the efficacy of all treatments decreased as the time interval between inoculation and treatment increased. This limitation confirms the need for more efficacious disinfection treatments that are capable of inactivating human pathogens on stored tomatoes.

Technical Abstract: Fresh tomatoes have repeatedly been associated with major outbreaks of salmonellosis; however, efforts to disinfect them with chlorine or other sanitizing agents have had only mixed success. Our objective was to determine whether hydrogen peroxide (H2O2) treatments would be more efficacious than conventional methods in disinfecting tomatoes containing human pathogens, and at the same time, be non-injurious to quality. Tomatoes were dip inoculated with Escherichia coli NRRL B-766 or a Salmonella cocktail, and then held for 0, 24 or 48 h at 4 or 24 C prior to treatment. Treatments included 200 ppm chlorine (Cl2) at 20 C for 3 min, water at 20 C for 3 min or at 60 C for 2 min, 1% H2O2 at 20 C for 15 min or at 60 C for 2 min, and 5% H2O2 at 60 C for 2, 3 or 5 min. In tomatoes held 48 h post inoculation, the chlorine treatment was only marginally more effective than an equivalent water rinse in reducing the target bacterial population, while the hot water and 1% H2O2 treatments achieved reductions no greater than 1.3 logs. However, application of 5% H2O2 at 60 C resulted in larger reductions. Efficacy of all treatments decreased as the time interval between inoculation and treatment increased. Greater reductions could not be achieved with 5% H2O2 by increasing the contact time or addition of surfactants, and these treatments caused some quality loss.