Process water in food manufacturing is a critical control point for product safety. Microbial contamination in this water can directly trigger foodborne disease outbreaks and product recalls. Traditional water disinfection technologies (such as chlorination and thermal disinfection) have limitations including the generation of disinfection by-products, equipment corrosion, and limited effectiveness against biofilms. Semiconductor deep-ultraviolet light-emitting diodes (UV-C LEDs, 260–280 nm) represent an emerging disinfection technology. With advantages such as no chemical residues, instant on/off capability, modular integration, and effective inactivation of microorganisms within biofilms, UV-C LEDs demonstrate unique value in food processing water systems. This article systematically outlines application strategies for UV-C LEDs in various water-use scenarios in food processing plants—including raw material washing, equipment rinsing, product cooling, and Clean-In-Place (CIP) systems—with a particular focus on their key mechanisms for inhibiting biofilm formation. It aims to provide technical references for water safety in the food industry.
I. Microbial Risks and Biofilm Challenges in Food Processing Water
Food processing plant water systems serve as important reservoirs for various foodborne pathogens. Studies show that common pathogens in process water include Pseudomonas aeruginosa, Escherichia coli, Salmonella spp., and Listeria monocytogenes. These microorganisms not only directly contaminate final products but also readily form biofilms on pipe inner walls, valves, nozzles, and other surfaces [1, 2]. Biofilms consist of microbial communities encased in extracellular polymeric substances (EPS) and exhibit 10–1,000 times greater resistance to conventional disinfectants, becoming persistent sources of contamination [3].
Research by Hile et al. (2025) on water dispenser systems confirmed that even when source water quality meets standards, microbial loads at terminal outlets can still increase significantly. The root cause lies in the continuous shedding and regeneration of biofilms inside the equipment [4]. This phenomenon is even more severe in food processing plants: high organic loads (protein and fat residues), intermittent water flow, and suitable temperatures (10–40°C) create ideal conditions for biofilm formation. Studies on endoscope reprocessing and dialysis water systems further indicate that biofilms can shelter multidrug-resistant organisms (MDROs) and periodically release planktonic cells through water flow shear forces, leading to downstream cross-contamination of products [5].
II. Principles of UV-C LED Technology and Its Advantages for Food Processing Applications
1. Mechanism of Action
UV-C LEDs emit photons in the 260–280 nm wavelength range. These photons are absorbed by pyrimidine bases in microbial DNA/RNA, forming cyclobutane pyrimidine dimers that block replication and transcription, achieving broad-spectrum inactivation [6]. Compared with traditional low-pressure mercury lamps (254 nm), the 265–275 nm band is closer to the DNA absorption peak (265 nm), theoretically improving inactivation efficiency by 15–20% [7].
2. Unique Advantages in Food Processing Scenarios
Compared with traditional mercury lamps and chemical disinfection methods (such as chlorination), UV-C LEDs offer several advantages with significant value for food processing:
- No chemical by-products: As a physical disinfection method, UV-C LEDs produce no harmful by-products such as trihalomethanes, avoiding impacts on product flavor and safety while aligning with clean-label trends.
- Instant on/off capability: Millisecond-level response supports intermittent operation, perfectly matching the intermittent water usage patterns in food processing and achieving energy savings of over 30%.
- Modular design and point-of-use disinfection: UV-C LEDs can be integrated into terminal outlets, spray heads, and hose connectors, enabling “point-of-use” disinfection that effectively blocks downstream biofilm propagation.
- Environmental compliance: Mercury-free design complies with RoHS directives, significantly reducing environmental compliance risks and simplifying waste management.
- Intelligent control: Integration with flow sensors, UV intensity monitoring, and IoT platforms allows real-time feedback on disinfection dose, meeting enterprise traceability requirements.
III. Application Strategies in Key Water-Use Scenarios in Food Processing Plants
1. Raw Material Washing and Pretreatment Water
Water used for washing fruits, vegetables, and meat is often heavily contaminated with organic matter, which reduces the efficacy of traditional disinfectants. UV-C LEDs can be installed downstream of reverse osmosis (RO) or microfiltration (MF) systems. For water with UV transmittance (UVT) >75% at 265 nm, they can achieve ≥4-log inactivation of E. coli [8]. An Italian study showed that after installing UV-C LED modules on a salad processing line, the detection rate of Listeria in final products dropped from 8.7% to 0.3% (P<0.01) [9].
2. CIP (Clean-In-Place) System Reuse Water Disinfection
CIP reuse water frequently contains protein and fat residues, making it prone to biofilm formation in storage tanks and pipelines. UV-C LEDs can be installed in the reuse circulation loop and combined with periodic hydrogen peroxide shock treatment to significantly inhibit Pseudomonas aeruginosa biofilm regrowth. Experiments demonstrated that a UV-C dose of 20 mJ/cm² combined with 0.5% H₂O₂ reduced biofilm biomass on stainless steel surfaces by 92%, outperforming either technology used alone.
3. Product Cooling and Ice-Making Water
Cooling water for ready-to-eat foods that comes into direct contact with product surfaces requires extremely strict microbial control. The U.S. FDA Food Code requires that cooling water must not contain coliforms. UV-C LEDs can be integrated at the inlet of ice machines to provide continuous disinfection.
4. Terminal Outlet Biofilm Control
As noted by Hile et al. (2025) in their water dispenser study, outlet nozzles are high-risk areas for biofilm formation, where microbial loads can reach 100 times those in the main pipeline [4]. Water taps, hose connectors, and other terminal components in food processing plants face similar risks. Recommended solutions include:
- Using pipelines with nano-silver coated linings to inhibit initial adhesion;
- Installing miniature UV-C LED modules 5–10 cm upstream of terminals (delivering ≥30 mJ/cm² at flow rates <5 L/min);
- Implementing a “UV pulse + reverse flushing” program during non-production hours each day to remove loose biofilms.
IV. Implementation Challenges and Evidence-Based Solutions
1. Impact of Water Quality Fluctuations
UV transmittance (UVT) in food processing water often fluctuates seasonally or with process changes, reducing UV penetration. Solutions include:
- Installing a 5 μm pre-filter upstream to maintain UVT >80%;
- Using multi-wavelength UV-C LED arrays to enhance tolerance to turbidity;
- Installing online UVT sensors for dynamic adjustment of LED power.
2. Long-Term Biofilm Control
Single UV disinfection struggles to completely remove mature biofilms. A recommended “three-tier defense” strategy is advised:
1. Prevention layer: Use 316L stainless steel or antimicrobial polymers in pipelines to reduce initial colonization;
2. Inhibition layer: Apply continuous low-dose UV (5–10 mJ/cm²) to inhibit planktonic cell adhesion;
3. Removal layer: Perform weekly high-dose UV pulses (40 mJ/cm²) combined with acidic cleaning agent shocks.
Combining these three approaches can effectively reduce biofilm formation and accumulation in pipelines.
V. Conclusions and Future Outlook
UV-C LED technology, through its chemical-free nature, precise control, and point-of-use integration capabilities, provides an innovative solution for biofilm control in food processing water systems. Evidence-based studies demonstrate that it can significantly reduce microbial loads in scenarios such as raw material washing, CIP reuse water, and cooling water. However, it must be combined with material selection, water flow design, and regular maintenance to form a comprehensive strategy.
Future research should focus on:
- Optimization of multi-technology synergies (UV/ozone/membrane filtration) for high-organic-load water;
- Machine learning-based prediction of biofilm formation and adaptive disinfection dose control;
- Full life-cycle cost analysis to promote wider adoption of the technology among small and medium-sized food enterprises.
Food water safety is the cornerstone of the “farm-to-table” chain. As a representative of green disinfection technologies, UV-C LEDs are poised to achieve a win-win outcome between food safety assurance and sustainable development.
References:
1. Shi X, Z.X., Biofilm formation and food safety in food industries. Trends in Food Science & Technology, 2009(20(9): 407-413).
2. Hossain, M.I.M.M., Listeria monocytogenes biofilm inhibition on food contact surfaces by application of postbiotics from Lactobacillus curvatus B. 67 and Lactobacillus plantarum M. 2. Food Research International. 2021(148, 110595).
3. Liu S, G.C.B.N., Understanding, monitoring, and controlling biofilm growth in drinking water distribution systems. Environmental science & technology, 2016(50(17): 8954-8976).
4. Hile, T.D.L.R., Microbiological quality of drinking water from water dispensers. AIMS microbiology, 2025(11(4), 891).
5. Rattanakul, S.O.K., Inactivation kinetics and efficiencies of UV-LEDs against Pseudomonas aeruginosa, Legionella pneumophila, and surrogate microorganisms. Water research, 2018(130, 31-37.).
6. Beck, S.E.R.H., Evaluating UV-C LED disinfection performance and investigating potential dual-wavelength synergy. Water research, 2017(109, 207-216).
7. Wang, C.P.L.J., Effect of UV-C LED arrangement on the sterilization of Escherichia coli in planar water disinfection reactors. Journal of Water Process Engineering, 2023(56, 104399).
8. Oh, Y.K.H.C., Evaluating Disinfection Performance and Energy Efficiency of a Dual-Wavelength UV-LED Flow-Through Device for Point-of-Use Water Treatment. 2025(17(20), 2965).
9. Lehto M, K.R.M.J., Hygienic level and surface contamination in fresh-cut vegetable production plants. Food control, 2011(22(3-4): 469-475.).
