Testing the Ability for Novel "Green" Technologies to improve Beef's Safety and Shelf Life

Background

Properly installed and maintained food safety interventions are very effective at producing beef carcasses with extremely low microbial counts in commercial beef packing facilities. The big risk is beef will become re-contaminated as carcasses move through the plant to be fabricated into smaller cuts. Conveyor belts are hard to clean. Metal housings and rollers provide a place where pathogenic or spoilage bacteria can hide, grow and produce protective biofilms, which can re-contaminate beef. Some cleaning processes use chemicals that may corrode equipment. Some bacteria may also form spores that are impervious to cleaning processes and may later germinate in vacuum packs and cause blown pack spoilage.

In an earlier BCRC proof-of-concept study, researchers found that two minutes of ultraviolet-C light from a light-emitting diode (LED) led to a 99.9% reduction in Escherichia coli (E. coli) biofilms on polystyrene surfaces. Applying an atmospheric cold plasma (ACP) water mist for one minute reduced biofilms on food contact surfaces by 99%. This project followed up on those preliminary results.

Objectives

• Validate novel dry (e.g., ultraviolet-C LED treatment) and wet (e.g., ACP-activated water mist) surface sanitation methods.
• Develop and validate novel dry (e.g., ACP-activated chilled air) and wet (e.g., ACP-activated water mist/spray) carcass chilling methods with enhanced microbial inactivation (“PlasmaChil”).
• Develop and scale-up a treatment unit together with industry.

What They Did

This study tested new, chemical-free ways to remove harmful bacteria and biofilms from surfaces and food systems. In the laboratory, bacteria such as E. coli were grown on common food-contact materials (i.e., stainless steel and polystyrene) to simulate contamination in meat-processing environments. These surfaces were then treated using different methods, including plasma-activated water (PAW), ultraviolet (UV-C) light and other sanitizers, to compare how effectively each approach inactivated bacteria.

They also developed a plasma-activated fine-mist system to help disinfect hard-to-reach areas. In addition, a new high-pressure plasma chill spray treatment was developed, combining antimicrobial plasma-treated water, cooling and high-pressure spraying to enhance cleaning and sanitation.

The study also examined whether various sanitizing methods are effective against Clostridium estertheticum spores. These spores are more resistant to treatment and are an important cause of spoilage in vacuum-packed beef. The sanitizers were tested on surfaces, in liquids and on beef products. Additional experiments evaluated the effectiveness of treatments during refrigerated storage of packaged beef.

Across all experiments, bacterial survival was measured before and after treatment to determine effectiveness. The study also assessed how factors such as surface type, food residues and treatment conditions influence sanitation performance.

What They Learned

This study showed that new, chemical-free sanitation technologies can significantly improve the removal of harmful bacteria and biofilms compared to conventional harsh chemical methods. Plasma-activated water-based treatments were effective in reducing E. coli biofilms on metal surfaces, although their performance varied by surface type. UV-C light also demonstrated a strong ability to kill both free bacteria and cells in biofilms, highlighting its potential as a practical and effective sanitation tool.

Using a fine, plasma-activated mist and a high-pressure plasma chill spray provided better surface coverage, especially in hard-to-reach areas. This enhanced overall cleaning effectiveness and biofilm inactivation. The plasma chill spray system combining plasma-treated water, cooling and high-pressure spraying, achieved very high reductions in bacterial counts (i.e., 99.99 to 99.9999%), even under challenging conditions such as dried biofilms and food-residue-covered surfaces.

UV-C LED treatments and specific sanitizers effectively reduced C. estertheticum spores on surfaces, achieving a 99.99% reduction in C. estertheticum counts. However, all treatments were less effective on actual beef. This highlights the challenge of controlling microbes in complex food environments.

What It Means

Plasma-based and UV technologies have strong potential to replace or reduce the use of chemical disinfectants. Advantages include no chemical residues, improved water-use efficiency and environmental sustainability. However, further work is needed to scale up and optimize these technologies for real-world conditions, especially for direct use on food products and food-contact surfaces.