Pathogen transfer risks associated with specific tomato harvest and packing operations.

The establishment standards related to removal of dirt and debris from tomato fruits during field pack operations and re-use of tomato cartons in re-pack operations within the Tomato Good Agricultural Practices and Best Management Practices document is essential for the responsible harvesting, handling and packing of fresh tomatoes. Understanding risks potential transfer of pathogens onto tomatoes from used tomato cartons r cloths used to remove debris is a fundamental management prerequisite to providing customers with safe tomatoes. There is inadequate science-based data to base current standards and audit inspection criteria for re-use of tomato cartons and removal of dirt and debris from tomatoes. The purpose of this research project is to define risks associated with dirt and debris removal in the field and re-use of tomato cartons in re-pack operations. The research outcomes will allow for the assignment of research-based metrics for in field debris removal and re use of tomato cartons for the fresh tomato industry.

Use of the term “cross-contamination” during traceback investigations and in the general discussion of possible routes of produce contamination is common from industry, academia and government officials. For fresh tomatoes, much attention has been focused on potential routes of “cross-contamination” with Salmonella during production, harvest and post-harvest packaging and processing. Little data which quantify cross-contamination risks specific to practices used during harvest and packing tomatoes exist. The lack of specific, quantified cross-contamination data related to risks associated with pathogen transfer from dirty cleaning cloths or soiled re-used cartons remains a barrier in the development of specific best practices for the fresh tomato industry. Laboratory based experiments will provide scientifically-based metrics to minimize risks related to infield debris removal during harvest of field-packed tomatoes, and re-use of tomato cartons in re-pack operations. Specifically, transfer coefficients between Salmonella inoculated clean and dirty cloths and tomatoes, the fate of Salmonella on clean and dirty cloths, transfer coefficients between dirty used tomato cartons and Salmonella and the fate of Salmonella on dirty used tomato cartons will be evaluated. A comprehensive tomato food safety review will also be generated. In summary, this proposal will develop scientifically-based metrics on how debris from tomatoes can be performed in the field without increasing the relative food safety risk and how tomato cartons can be re-used safely in repacking operations directly applicable for the fresh tomato industry.

1. Determine (i) transfer coefficients of Salmonella between inoculated clean and dirty clothes to tomatoes; (ii) transfer coefficients of Salmonella during subsequent touches of tomatoes to inoculated clean and dirty cloths; and (iii) fate of Salmonella on inoculated clean and dirty cloths over typical time periods at typical temperatures between cloth cleaning. 

2. Determine (i) transfer coefficients between inoculated dirty, used tomato cartons and Salmonella stored for various times at temperatures; and (ii) the fate of Salmonella on used tomato cartons in the presence of dirt, debris, and tomatoes at various temperatures and relative humilities. 

3. Develop a written comprehensive review covering food safety research and tomatoes.

The following summarized the findings of this study. 

1. Salmonella transfer between tomatoes, tomato cloths and cartons is highly dependent on moisture, with increased levels of moisture increasing transfer. To decrease risks associated with Salmonella transfer during tomato harvesting and packing, the presence of moisture on tomatoes, cloths and cartons should be minimized or avoided. 

2. Salmonella does not survive at high levels on cloths, regardless of the presence of debris. Survival is enhanced by storage at cooler temperatures where populations may persist for up to 7 days. Use of cloths, without cleaning between days, may be a source of contamination for the subsequently harvested tomatoes. 

3. Salmonella can transfer, at low levels, from clean and dirty cloths to at least 25 tomatoes subsequently touched with the same cloth. A contaminated cloth may be the source of contamination to multiple tomatoes touched with the cloth. Presence of debris on cloths did not significantly increases the risk of Salmonella transfer. 

4. The presence of debris on used tomato cartons, especially when stored at cooler temperatures, increases the survival of Salmonella; however, Salmonella can survive on tomato packing cartons for at least seven days even in the absence of debris. Reused tomato cartons may be a source of contamination for the subsequent tomatoes packed in these cartons. 

5. Under no conditions was the transfer of Salmonella from new tomato cartons greater than that from used or dirty cartons. Under some conditions, dirty containers transferred less Salmonella than new and used cartons; the presence of debris on used cartons does not significantly increase the risk of Salmonella transfer between cartons and tomatoes.