KEY TAKEAWAYS:
- Two light wavelengths — far-UVC light (222 nanometers) and blue light (405 nm) — hold promise for packinghouse brush sanitation.
- Brush material, brush color choice and light exposure duration appear to play a significant role in pathogen inactivation.
Referenced CPS Research:
Based on industry input, the Center for Produce Safety highlighted brush sanitation as a research priority. The following two projects take slightly different approaches to address that priority.
Tapping antimicrobial light
Govindaraj “Govind” Dev Kumar, Ph.D., at the University of Georgia, hopes to shed light on a potentially new packinghouse brush sanitation method that — when combined with traditional antimicrobials — may yield synergies.
He is leading research that examines the efficacy of far-UVC light (222 nanometers) and blue light (405 nm) on three pathogens: Salmonella enterica, Shiga toxin-producing E. coli (STEC), and Listeria monocytogenes.
Dev Kumar said he chose those wavelengths because of their germicidal activity. Compared to germicidal ultraviolet light, 222 nanometer light is not injurious to humans, and both 405 nm and 222 nm light cause less damage to plastics or other materials.
Joining him as co-investigators are Cameron Bardsley, Ph.D., with the U.S. Department of Agriculture-Agricultural Research Service; David Shapiro-Ilan, Ph.D., also with the USDA-ARS; and Claire Murphy, Ph.D., at Washington State University.
Midway through the two-year CPS-funded project, the researchers have looked at how wash and wax brush material, brush color and light duration may affect pathogen inactivation. In addition to more common nylon and horse-hair brushes, they also included polypropylene and polyethylene.
After dipping coupons or disks of individual brush material in a solution of one of the three pathogens, the researchers exposed them to various light durations to determine microbial die-off. While Dev Kumar said they’re still analyzing the data, he noted significant differences among the treatments already were apparent.
“We’re seeing some interesting results,” he said. “When we put the whole dataset together, we’ll be able to tease out which ones are the most effective.”
Their next step will be to validate the antimicrobial lights in cooperating commercial peach and apple packinghouses this summer. After employees perform normal end-of-shift sanitation and while brushes are still wet, lights will be turned on for eight hours.
The researchers will swab the brushes before and after light treatment to measure potential reduction of bacteria as well as yeast and mold, which are considered spoilage organisms.
“Putting in a second hurdle, we think, will reduce the presence of pathogens,” Dev Kumar said. “It’s cost effective and not a chemical, so it’s a residue-free antimicrobial treatment. We hope to provide the industry with another tool that will help them choose the right brush material and even the right color along with these treatments.”
KEY TAKEAWAYS:
- Packinghouse wash, dry and wax brushes undergo normal wear that make sanitation more difficult and potentially increases Listeria cross-contamination risks.
- The project will identify indicators of wear to guide brush replacement as a strategy to reduce Listeria harborage and cross-contamination.
Referenced CPS Research:
When to replace old brushes
During the season, packinghouse wash, dry and wax brushes undergo normal wear, making cleaning and sanitation more difficult and potentially increasing Listeria cross-contamination risks.
Knowing when to replace brushes can be difficult, given the additional costs of downtime and new brushes.
Through her CPS-funded project, Abby Snyder, Ph.D.,at Cornell University, hopes to develop a set of findings to help guide decision-making around brush replacement.
“What we hope to do is give people a set of options that aren’t just enhanced sanitation strategies but also replacement of wearable parts that are potential Listeria harborage points,” she said. “
To begin, Snyder identified deterioration markers among brushes with different uses, such as washing, drying and waxing in a collaborating packinghouse.
“While replacing these brushes definitely reduces counts and eliminates Listeria harborage, it can be expensive.” Snyder said.
In the second half of her project Snyder hopes to identify markers the industry can use to determine when brush replacement may be indicated.
Joining as co-investigator was V.M. Balasubramaniam, Ph.D., formerly at Ohio State University (now at University of Georgia). He conducted laboratory trials using steam to clean and sanitize brushes at various stages of wear. Initially, the steam was more effective at sanitizing the exterior brush filaments than portions closer to the core. But when Balasubramaniam placed the brushes in a cabinet to concentrate the steam, he observed greater and more uniform sanitation results.
The next step will be to trial the protocols with collaborating apple packinghouses and evaluate antimicrobial outcomes.