Evaluation of sanitation protocols for nonconventional food-contact surface materials used in produce packinghouses

There is a lack of guidance in the produce industry on cleaning and sanitizing porous food-contact surfaces in packinghouse environments. Current practices need to be validated to assess any associated microbial risks, and future guidance should be data-driven prior to implementation. This proposal focuses on evaluating cleaning and sanitizing practices for porous food-contact surfaces in packinghouses across the U.S., and the associated risks of product contamination influenced by surface/equipment characteristics in these environments. Semi-structured Interviews with growers at very small to medium operations as well as Extension Specialists across the U.S. working with produce growers will aid in characterizing the most common porous food-contact surfaces and current cleaning and sanitizing practices. The experimental approach in the laboratory will be informed by these interviews. First, the persistence and potential growth of microorganisms on six porous food-contact surfaces subjected to a variety of conditions relevant to produce production environments will be assessed. This work will be followed by evaluation of cleaning and sanitizing protocols for each of the six porous food-contact surfaces. The data generated from this research will help characterize the risks associated with porous food-contact surfaces and limit cross contamination during packing operations.

Limited knowledge is available in the peer-reviewed literature on cleaning and sanitizing (C&S) efficacy of unconventional, often porous, food-contact surfaces (FCS) in produce packinghouse environments. Based on discussions with the produce industry and produce safety extension specialists, C&S of packinghouse surfaces ‘as needed’ is subjective and largely based on visual inspection and convenience. There is a lack of guidance for C&S best practices on porous FCS in produce packing areas, and there is a need for evidence-based Sanitation Standard Operating Procedures (SSOP). This research will determine the effectiveness of C&S practices for common porous FCS found in the produce industry, specifically growers with medium, small, very small, and limited season operations. In the proposed work, a mixed methods approach will be used to verify porous FCS selection and parameters for evaluation. Specifically, semi-structured interviews will be conducted with 15 to 20 growers from medium, small, very small, or seasonally limited operations within Arkansas and the northeast U.S. These interviews will be transcribed followed by thematic analysis to identify common porous FCS, C&S practices, and reasons for surface selection. Based on these interview data and Extension Cooperator feedback, pathogen persistence and removal by C&S will be determined for porous FCS coupons (25 cm2) under a variety of experimental parameters. Pathogens include Listeria monocytogenes (5 strain cocktail), Salmonella enterica (5 strain cocktail), Shiga toxin-producing Escherichia coli (STEC; 4 strain cocktail), Tulane virus (TuV; human norovirus surrogate), and Aichivirus A (AiV; same virus family as Hepatitis A virus). Additional experimental factors include i) bacterial pre-growth conditions such as low water activity, minimal medium, temperature stress; ii) inoculation matrix (wet vs. dry); and iii) FCS cleanliness (clean vs. visibly dirty). Microbial persistence and/or growth (bacteria only) on six porous FCS over a 7-day period under four temperatures (32°C, 27°C, 21°C, 15°C) at 50% relative humidity will be determined. Efficacy of C&S treatments for surfaces under the aforementioned parameters will also be determined. Three sanitizers are proposed for evaluation with formulations including peroxyacetic acid + hydrogen peroxide, isopropyl alcohol, and chlorine dioxide. Upon study completion, specific, data-driven guidance for C&S of common, porous FCS utilized by growers with medium, small, very small, and limited season operations will be provided.

1. Utilize a mixed methods approach to confirm types of porous FCS in produce packing areas. 

2. Evaluate the efficacy of cleaning and sanitizing of porous FCS in produce packing areas.

This project evaluated pathogen persistence and sanitation effectiveness on common food-contact surfaces in produce packinghouses. Interviews with produce safety educators and packinghouse operators identified key barriers to effective sanitation, including limited financial resources, legacy equipment not designed for hygienic cleaning, language and training gaps, and reliance on visual inspection rather than validation tools. Laboratory studies showed that surface material strongly influences pathogen survival. High-density foam consistently supported the longest persistence of Listeria monocytogenes, Salmonella, and Shiga toxin–producing Escherichia coli (STEC), while stainless steel and rubber showed intermediate survival. Pathogens were capable of surviving for several days, particularly under dry contamination conditions. Virus persistence was influenced primarily by virus type and temperature, with longer survival on dirty surfaces and at cooler temperatures. Cleaning followed by sanitizing consistently produced the greatest pathogen reductions. 

Packinghouse operations should prioritize the use of hygienically designed, nonporous food-contact surfaces whenever possible, as porous materials such as high-density foam can harbor microorganisms and support prolonged pathogen survival. When replacement of these materials is not feasible, operations should implement more frequent and thorough cleaning and sanitation procedures and consider alternative sanitizers or equipment modifications that improve cleanability. Effective sanitation programs should emphasize the importance of cleaning prior to sanitizer application, since the removal of organic matter and debris is critical for sanitizers to work effectively. In addition, packinghouses should strengthen sanitation standard operating procedures (SOPs) and provide clear training to employees on proper sanitizer preparation, application methods, and required contact times to ensure consistent implementation of sanitation practices. Packinghouses should also move beyond relying solely on visual inspection to evaluate cleanliness and instead adopt sanitation verification approaches such as environmental monitoring programs or other validation tools to confirm that cleaning procedures are effective. Finally, maintaining clean packing environments by minimizing organic debris, managing moisture, and controlling environmental conditions can help reduce both bacterial and viral persistence on surfaces and lower the risk of cross-contamination during produce handling and packing.