UV-C Decontamination SOP

Cheatsheet Content

STANDARD OPERATING PROCEDURE (SOP) Validation of UV-C Surface Decontamination Efficacy on Ready-to-Eat (RTE) Cake Products Company Name: Shanghai Gesund Industrial Co., Ltd. Equipment: PureLED Pro – UV-C Surface Disinfection System SOP No.: FSP-VAL-UV-001 Version: 1.4 Effective Date: 25 December 2025 Prepared by: Food Safety & Validation Laboratory Reviewed by: Quality Assurance Department Approved by: __________________________ Date: _________________________________ 1. PURPOSE This Standard Operating Procedure (SOP) defines a scientifically accepted method to validate the effectiveness of the PureLED Pro UV-C system for reducing microbial contamination on ready-to-eat (RTE) cake surfaces using controlled surface inoculation, UV exposure, and microbiological enumeration. 2. SCOPE This procedure applies to finished cakes and similar bakery products and evaluates only those surfaces that are directly exposed to UV-C radiation, including: Top horizontal surfaces Side surfaces where unobstructed UV exposure occurs The validation is conducted under production-representative conditions of 2 cm UV distance and 0.5 second exposure time. 3. SCIENTIFIC PRINCIPLE Ultraviolet-C (UV-C) radiation in the wavelength range of 200–280 nm inactivates microorganisms by damaging nucleic acids, thereby preventing replication. UV-C is a line-of-sight technology and does not penetrate food or shaded areas. Therefore, effectiveness must be validated using surface-specific sampling methods applied only to exposed areas. 4. EXPERIMENTAL DESIGN A four-group controlled study design is used. A minimum of three samples per group is required. Group Description Purpose A Inoculated + UV treated Post-treatment result B Inoculated + not treated Baseline control C Not inoculated + not treated Natural flora control D Not inoculated + UV treated Natural flora reduction Note: For Groups A and B, inoculation is always performed before UV treatment. 5. TEST MICROORGANISMS This protocol may be performed using pathogenic microorganisms or approved non-pathogenic surrogates, depending on laboratory capability and regulatory requirements. Typical organisms include: Escherichia coli Salmonella spp. (or validated surrogate) Listeria monocytogenes (or validated surrogate) Staphylococcus aureus Total aerobic surface flora The selected microorganism(s) must be clearly documented in the validation report. 6. INOCULUM LEVEL JUSTIFICATION ($10^8$ CFU/mL) An inoculum concentration of approximately $10^8$ CFU/mL is used to represent a worst-case contamination scenario. This level: Ensures detectable survivors after UV exposure Allows accurate log-reduction calculation Prevents false-negative validation outcomes Application of 0.1 mL of this suspension to a 25 cm² surface delivers approximately $10^7$ CFU, consistent with internationally accepted food-surface UV validation practices. 7. PROCEDURE 7.1 Surface Inoculation Place a sterile 5 cm × 5 cm (25 cm²) template on the exposed cake surface Apply 0.1 mL of microbial suspension evenly within the template Allow the surface to dry for 30–45 minutes under hygienic conditions 7.2 UV Treatment Apply UV-C exposure at 2 cm distance for 0.5 seconds using the PureLED Pro system 7.3 Sampling Immediately after UV treatment, swab the defined surface using a sterile swab moistened with neutralizing buffer Transfer the swab into 10 mL buffered peptone water Mix thoroughly to release microorganisms 8. ENUMERATION AND CALCULATION Perform serial dilutions Plate on suitable agar media Incubate at $30 \pm 1$ °C for $48 \pm 2$ hours Use plates containing 30–300 colonies Calculation: CFU/cm² = (Colony count × Dilution factor × 10) $\div$ 25 Log reduction is calculated by comparing treated and untreated results. 9. INTERPRETATION OF RESULTS Log Reduction Percentage Reduction Interpretation $\ge 1$ log $\ge 90\%$ Good $\ge 2$ log $\ge 99\%$ Very Good $\ge 3$ log $\ge 99.9\%$ Excellent $\ge 4$ log $\ge 99.99\%$ Outstanding For short industrial exposure times such as 0.5 seconds, a 1–2 log reduction is considered technically effective and commercially meaningful. 10. LIMITATIONS AND BIOSAFETY UV-C treatment affects only directly exposed surfaces and does not disinfect shaded areas or internal product structures. All work involving pathogenic microorganisms must be conducted in appropriately rated laboratories. Approved surrogates may be used where required. REFERENCES (AUTHORITATIVE AND VERIFIABLE) ISO 18593:2018 – Microbiology of the food chain: Surface sampling https://www.iso.org/standard/64950.html FDA – Bacteriological Analytical Manual (BAM), Chapter 1 https://www.fda.gov/food/laboratory-methods-food/bam-chapter-1-food-samplingpreparation-sample-homogenate AOAC Official Method 965.49 – Aerobic Plate Count https://www.aoac.org/official-methods-of-analysis International Ultraviolet Association (IUVA) – UV Disinfection Fundamentals https://iuva.org/UV-Disinfection Guerrero-Beltrán & Barbosa-Cánovas (2004) – UV light in food processing Food Science and Technology International https://journals.sagepub.com/doi/10.1177/1082013204043111 Koutchma, T. (2009) – UV technology for food surface treatment Food and Bioprocess Technology https://link.springer.com/article/10.1007/s11947-008-0178-3 Journal of Food Protection (2020) – UV inactivation on food surfaces https://meridian.allenpress.com/jfp/article/83/1/1/427758 PubMed (NIH) – Validation of UV-C processes on food surfaces https://pubmed.ncbi.nlm.nih.gov/35630893/ Bintsis et al. (2000) – Effect of UV on microbial quality of foods Journal of the Science of Food and Agriculture Codex Alimentarius Commission – General Principles of Food Hygiene (CXC 1-1969) https://www.fao.org/fao-who-codexalimentarius