IAFP 2009 Program Book and Abstract Book - AB44

process with no obvious visual injury. Storage of untreated inoculated tomatoes at 13, 20, and 30°C for up to 6 days post inoculation caused a significant (P < 0.05) increase in S. Poona populations (up to 3 log CFU/g) as compared to storage at 4°C. Significance: These results indicate that surface pasteurization will enhance the microbiological safety of tomatoes with no adverse effect on the 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. T5-10 Sanitizer Solutions Containing Detergents for Inactivation of Escherichia coli O157:H7 on Romaine Lettuce Lindsey A. Keskinen and BASSAM A. ANNOUS USDA-ARS-ERRC, Food Safety Intervention Technologies, Wyndmoor, PA, USA Introduction: Numerous Escherichia coli O157:H7 outbreaks have been linked to consumption of fresh lettuce. The development of effective and easily implemented wash treatment could reduce such incidents. Purpose: The purpose of this study was to evaluate the addition of food-grade detergents to sanitizer solutions for inactivation of E. coli O157:H7 on romaine lettuce. Methods: Freshly-cut leaves of romaine lettuce were dip-inoculated to achieve a final cell concentration of 7.8 ± 0.2 log CFU/g, air-dried for 2 h, and stored overnight at 4°C. Leaves were then washed for 2 min in an experimental short chain fatty acid formulation (2CL) or in one of the following solutions with or without 0.2% dodecylbenzenesulfonic acid or 0.2% sodium 2-ethyl hexyl sulfate: 1) deionized water; 2) 100 ppm chlorine dioxide; 3) 100 ppm chlorine; 4) 200 ppm chlorine. Following wash treatment, samples were blended in neutralizing buffer (1:3) and surface plated on the selective medium CT-SMAC. Results: The efficacies of wash treatments, with or without the detergents, in inactivating E. coli O157:H7 cells on lettuce leaves were not significantly different. The most effective wash solution was 2CL, which was capable of reducing E. coli O157:H7 populations by more than 5 log CFU/g (none detected by direct plating). The rest of the wash treatments resulted in a population reduction of less than 1 log CFU/g. Significance: The effectiveness of 2CL surpasses that of other sanitizer treatments tested in this study and requires further research to optimize treatments to preserve lettuce quality. Conventional detergents did not enhance the efficacy of any of the wash treatments tested during this study. The addition of such detergents to a conventional commercial wash treatment might not be advantageous. T5-11 Pinpointing Sources of Contamination on Leafy Green and Fresh Market Tomato Farms LINDSAY ARTHUR, Moustapha Oke and Shu Chen OMAFRA, Guelph, ON, Canada Introduction: Leafy greens and fresh market tomatoes have been the source of high profile outbreaks. The causes of these outbreaks are often traced back to the farm; however, information is limited as to the key sources of on-farm contamination. Purpose: To identify key areas of concern on leafy green and fresh market tomato farms, from growth to packing, such as in the field, at harvest, washing, hydro-cooling and packing; and to link environmental sources of contamination to the contamination found on the produce. Methods: Four farms were involved in the study. Samples of produce in the field, at harvest, after hydrocooling, washing and packing from each farm, were obtained along with corresponding environmental samples and tested for generic E. coli. Environmental samples consisted of irrigation water, soil, hand swabs, post harvest water, harvest bin swabs, knife swabs, conveyor belt swabs and ice samples. Positive samples for E. coli were genotyped using Amplified Fragment Length Polymorphism (AFLP), and similarity between AFLP fingerprints among sample types were calculated using the bandbased “Dice coefficient”, enabling identification of contamination sources. Results: For all four farms, a total of 2,098 samples were analyzed for generic E. coli. E. coli isolates were very diverse on each farm, with 309 (lettuce farm), 689 (tomato farm), 1,002 (parsley farm), and 1,968 (spinach farm) different isolates identified. For each farm, the points of harvest and beyond were the most significant areas of concern. Genotyping results demonstrated that pre and post harvest water, along with conveyor belts and hands, are the main sources of contamination. Significance: These results provide data to policy makers, risk assessors, risk managers and farmers in terms of the areas on leafy green and fresh market tomato farms that are likely to affect food safety. T5-12 Attachment of Norovirus in Manure and Biosolids to Lettuce DSC JIE WEI and Kalmia E. Kniel University of Delaware, Animal and Food Sciences, Newark, DE, USA Introduction: Norovirus is a major foodborne pathogen, with outbreaks widely associated with fresh produce. The attachment of norovirus to plants in fields may be a cause of contamination of fresh produce. Knowledge of how norovirus in biosolids/manures attaches to lettuce and the mechanisms of internalization into plant tissue is needed to protect public health. Purpose: To study the attachment behaviors of norovirus recovered from biosolids and manure, specifically addressing virus attachment and internalization associated with lettuce leaves. Technical 44 — Abstract Book

IAFP 2009 Program Book and Abstract Book

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