Color and material optimization of brushes for improved light-based sanitation

Brushes are used in fruit and vegetable packinghouses to remove dirt from fruit and vegetable surfaces and apply wax to the produce to improve its shelf life. Waxer and washer brushes clean or coat thousands of fruits or vegetables before they are sanitized. Previous research has shown that even frequently sanitized brushes can harbor high microbial populations. Since brushes are hard to clean using only conventional sanitizers, light-based antimicrobial interventions could improve brush hygiene. Far range UVC light (222 nm) and blue light (405 nm) can kill bacteria. They can be safely used in food processing facilities unlike conventional germicidal UV (254 nm) that can cause cancer. We propose to improve the ability of Far UVC light and blue light in inactivating foodborne pathogens on brushes by selecting the right brush color and brush material. The color of a surface and the material can influence the amount of light absorbed. Our findings on brush color and material will be adopted by collaborating packing houses in Georgia and Washington. Waxer and washer brushes exposed to antimicrobial light will be evaluated for reduced bacterial counts. The outcome of the study would be improved brush hygiene and consequentially safer produce and less spoilage.

Brushes are high-frequency fruit contact surfaces that can harbor spoilage and pathogenic microorganisms. Preliminary research has shown that a buildup of microorganisms can potentially increase on brushes over a production season despite cleaning and sanitation. The use of antimicrobial light could help prevent the onset of persistent contamination and serve as a cost-effective hurdle to complement brush sanitation practices. Light at wavelengths of 222 nm (Far UVC) or 405 nm (blue light) have antimicrobial activity and can be utilized to decontaminate hard-to-reach spaces such as brush filaments. The antimicrobial activity of Far UVC light at 222 nm results from enzyme inactivation, lipid peroxidation and DNA damage in microbial cells due to reactive oxygen species (ROS) production. Similarly, the exposure of microbial cells to blue light at 405 nm results in the excitation of endogenous photosensitizers leading to the production of ROS that causes cell death. Unlike germicidal UVC (254 nm) both 222 nm light and blue light do not have adverse effects on humans or cause heating and pitting of equipment. Further, 222 nm and 405 nm light can be emitted by low-power light-emitting diode (LED) lamps. These lamps do not have the risk of radiating heat or contain mercury unlike conventional 254 nm germicidal UV lamps. This proposed study aims to optimize the antimicrobial efficacy of 222 nm and 405 nm light through the selection of brush filament color and material. Preliminary research has indicated that the surface color of an HDPE coupon impacted the efficacy of antimicrobial light treatments. Blue color HDPE coupons exposed to 405 nm light had the highest reduction of L. monocytogenes while white coupons had the least reduction. Hence evaluating parameters that improve light absorption in brushes could positively improve the efficacy of antimicrobial light-based interventions. Further, the optimized interventions will be evaluated in packinghouse operations in the states of Georgia and Washington for their ability to impede pathogen and spoilage organism persistence and build-up throughout the packing season of tree fruit. The results gathered from this two-year project will help determine light wavelengths and brush design that could result in the effective control of bacterial buildup on packinghouse brushes. The findings from this project will be implemented in peach and apple packing facilities in Georgia and Washington respectively and validated through the packing season. The outcome of this study would be a better understanding of brush design parameters to improve the sanitation of washer and waxer brushes using antimicrobial light.

Objective 1: Evaluate the influence of brush filament color and brush filament material in affecting the antimicrobial efficacy of blue light (405 nm) and far-UVC light (222 nm) against Salmonella enterica, Shiga toxin-producing Escherichia coli (STEC), and Listeria monocytogenes. 

Objective 2: Evaluate synergistic mitigation between residual peroxyacetic acid on brushes and antimicrobial lights. 

Objective 3: Validate the effectiveness of 405-nm blue light and 222-nm far-UVC in reducing microbial buildup on washer and waxer brushes in peach and apple packinghouses through the packing season.

This project is ongoing. A final report will be provided when the project is finished.