Hot water surface pasteurization vs. chlorine wash for reducing populations of Salmonella Poona on artificially inoculated tomatoes

Authors: Annous, Bassam

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 3/10/2009
Publication Date: 7/12/2009
Citation: Annous, B.A. 2009. Hot water surface pasteurization vs. chlorine wash for reducing populations of Salmonella Poona on artificially inoculated tomatoes. [abstract]. International Association for Food Protection. p. 1.

Interpretive Summary:

Technical Abstract: Numerous outbreaks of salmonellosis have been associated with the consumption of fresh tomatoes contaminated with Salmonella. Commercial washing processes for tomatoes are limited in their ability to inactivate and/or remove this human pathogen. Our objective was to develop a hot water surface pasteurization process for enhancing microbiological safety of tomatoes. Fresh green tomatoes, dip inoculated with Salmonella Poona RM 2350 or to a final cell concentration of ca. 5 log CFU/gm were stored at 4 and 20C for up to 24 h prior to processing. Six inoculated tomatoes were treated for 3.5 min in 70C water or 20 ppm chlorine solution, and individual tomatoes were blended in peptone water (1:1) for 1 min. Enumeration of non-injured cells was done by plating on the selective media XLT-4 incubated at 35C overnight. Injured cells were recovered by plating on non-selective media TSA and incubating at 35C for 2 h and then plates were overlaid with XLT-4 and were incubated at 35C overnight. Reductions in S. Poona populations following treatments in water at 70C and 20 ppm chlorine solution were 6 and 1 log CFU/gm, respectively. Hot water treated tomatoes that were stored at 20C for 5 days showed normal maturation process with no obvious visual injury. Storage of untreated inoculated tomatoes at 13, 20, and 30C for up to 6 days post inoculation caused a significant (p<0.05) increase in S. Poona populations (up to 3 log CFU/gm) as compared to storage at 4C. These results indicate that surface pasteurization will enhance the microbiological safety of tomatoes with no adverse effect on maturation process, and will extend the shelf life of this commodity as well. Storage data indicated that tomatoes should be refrigerated as soon as possible following harvesting to suppress the growth of any possible contaminant.