Bio-based antimicrobial coatings for reducing risk of cross-contamination during harvesting

Cross-contamination during harvesting is a major food safety risk. This risk may result due to persistence of pathogens on harvesting equipment and food contact surfaces or introduction of pathogens on harvesting equipment and food contact surfaces during harvesting from soil, humans or other environmental factors. The overall goal of this project is to develop field deployable food ingredient based antimicrobial coatings to manage cross-contamination risks during harvesting. These antimicrobial coatings are based on a combination of selected food grade ingredients with a commonly used chlorine based sanitizer. The proposed research plan will develop coating formulations that can be readily deposited on legacy equipment and diverse food contact surfaces includes plastic and stainless steel and maintain antimicrobial properties during a harvesting shift. These coatings will also be designed to be easily removable during standard sanitation procedures. The research plan will demonstrate effectiveness of these antimicrobial coatings to achieve over 3 log inactivation of persistent pathogens including their biofilms on the surface of knifes and harvester conveyor belt, prevent formation of biofilms during operations and reduce cross-contamination of the food contact surface. The research plan will also test these coatings in a field trial and develop cost estimates as well as evaluate any potential chemical residue form chlorine bound to the coating material or its byproducts on fresh produce. Success in this approach will provide a field deployable solution to address the challenges of cross-contamination during harvesting.

Cross‐contamination of fresh produce during harvesting is a major food safety risk. This risk can result due to persistence of pathogens on equipment surfaces, sanitation challenges due to complexity of equipment design and risks of introducing pathogens from soil, contaminated produce or humans. Incremental changes in sanitation of harvesting equipment may not be adequate to address these risks. To address these diverse risks during harvesting, we propose to develop flexible antimicrobial coatings based on a combination of selected food grade ingredients with a commonly used chlorine based sanitizer. The central hypothesis is that selected food grade ingredients charged with chlorine can form flexible antimicrobial coatings to prevent cross‐contamination of fresh produce from both exogenous sources of pathogens such as soil, as well as residual/persistent population of pathogens on equipment surfaces. The specific objectives are to (a) demonstrate effectiveness of forming antimicrobial coatings on harvester conveyor belts and cutting knifes using simple spraying or dip coating methods; (b) evaluate antimicrobial and anti‐biofilm activities of the coatings on selected harvesting food contact surfaces and demonstrate efficacy of the approach to reduce cross‐contamination in a pilot scale operations simulating harvesting conditions and (c) field testing of the antimicrobial coating solution using harvesting knifes to demonstrate effectiveness in reducing build‐up of microbes on harvesting knifes during a shift. The success of this will project provide a novel field deployable approach to manage the food safety risks during harvesting operations by effectively controlling cross‐contamination risks from food contact surfaces such as harvesting knifes and conveyor belts.

1. Develop approaches for rapid and uniform deposition of antimicrobial food ingredient–based coatings on harvesting knives (stainless steel), harvester conveyor belts (polyethylene), and sprockets/grooves at the turning end of conveyors, and evaluate stability of antimicrobial coatings during simulated field operations. 

2. Demonstrate antimicrobial effectiveness of the food ingredient–based coatings against a diversity of pathogens (i.e., exogenous sources and contaminated surfaces prior to coating), and evaluate the prevention of cross-contamination of fresh produce upon contact with coated surfaces as well as the overall quality of the produce upon contact. 

3. Field-test the coating approach to demonstrate effectiveness on harvesting knives, and estimate costs of implementing this solution for harvesting knives and harvester conveyors.

● Rapid and uniform coating formulations were developed using food-grade biopolymers including beeswax, gelatin, gelatin/soy protein, and zein, and/or yeast-based microcarriers including YCs and YCWPs for diverse food-contact and handling surfaces. 

● The mechanical stability of the coating formulations was demonstrated in the simulated processing operations. 

● Rapid inactivation (<5 min) of the diverse pathogenic bacteria (E. coli O157:H7 and L. innocua) was demonstrated on diverse SS and PP surfaces in the presence of organic matter. 

● SS and PP surfaces coated with the antimicrobial formulations effectively reduced the risk of cross-contamination of the fresh produce with hazardous bacteria in the simulated fresh produce-handing operation. 

● Zein-based coating effectively reduced the microbial accumulation on SS harvesting knife during lettuce harvesting/trimming operations and on SS fruit sorting table during peach grading operations without affecting the quality of the fresh produce.