By Tatiana Koutchma, Richard Mariita, Peter Gordon and Britt Hafner, UV4Good
While UV-C light (200 to 280 nm) is a global standard for inactivating pathogens in water and food, nongermicidal applications of selective wavelengths in the UV-C and UV-B (280 to 315 nm) ranges remain an untapped frontier in food systems. These nongermicidal effects include wavelength-dependent modification of enzymatic activity and targeted nutritional enhancements, such as vitamin D enrichment, offering opportunities to improve product quality, shelf life and nutritional value without relying on thermal processing.
Effects of UV Light on Enzymes
Enzymatic activity significantly influences shelf life and stability in fruit and vegetable juices, nut-based beverages and other liquid foods. Endogenous enzymes – such as polyphenol oxidase (PPO), peroxidase (POD) and lipoxygenase – drive undesirable changes, including enzymatic browning, off-flavor development and lipid oxidation.
UV-C wavelengths are strongly absorbed by peptide bonds and aromatic amino acids (tryptophan, tyrosine and phenylalanine), often leading to irreversible denaturation, aggregation and loss of catalytic function. In contrast, UV-B (280 to 315 nm) and UV-A (315 to 400 nm) wavelengths exert more selective and moderate effects, allowing partial modulation rather than complete destruction.
In clear or lightly turbid liquids (e.g., fruit juices, plant-based beverages), nongermicidal UV-B and UV-A treatments can suppress enzymatic reactions while minimizing severe protein damage associated with UV-C. A key example is coconut water, where PPO and POD contribute to pink discoloration, turbidity and flavor deterioration during storage. Studies show that controlled UV treatments reduce PPO activity, thereby improving color stability and delaying quality degradation while preserving fresh taste and heat-sensitive nutrients. 1 For instance, comparative trials using an excimer lamp (222 nm) and UV-C LEDs (257 nm, 267 nm, 286 nm) in continuous-flow systems demonstrated clear wavelength-dependent differences in enzymatic inactivation efficiency and overall performance. The 222 nm excimer lamp proved most effective for POD inactivation (e.g., ~60% at 29.2 mJ/cm²), while higher fluences (>200 mJ/cm²) were required with LEDs to achieve similar results. 2 The fundamental reason is that 222 nm is closer to the absorption line of enzymes, delivering higher photon energy.
Similar wavelength-selective effects have been reported in apple and pear juices (reduced PPO and POD to slow browning), beer (influence on haze formation) and vegetable juices/oils (moderated lipoxygenase to limit oxidative off-flavors). These examples highlight UV as a nonthermal tool for fine-tuning enzymatic activity, extending shelf life, and maintaining sensory and nutritional quality.
Effects of UV Light on Vitamins
UV–vitamin interactions are highly wavelength-, structure- and matrix-dependent, resulting in either degradation or beneficial transformations.
UV-C wavelengths typically are associated with photodegradation of light-sensitive vitamins – especially water-soluble ones, such as riboflavin (B₂), ascorbic acid (vitamin C) and folates – via direct photon absorption, oxidation or the formation of inactive photoproducts. Vitamin C shows particular sensitivity at 254 nm but greater stability at longer wavelengths. Fat-soluble vitamins (A and E) exhibit better photostability under UV-A, although indirect oxidation via reactive oxygen species can occur in oxygen-rich matrices. Protein binding, encapsulation and light scattering further modulate stability and penetration.
By contrast, UV-B and UV-A wavelengths enable selective, nongermicidal nutritional enhancement. The most established example is UV-B-induced photoconversion of provitamin D precursors – 7-dehydrocholesterol in animal tissues and ergosterol in fungi – into bioavailable vitamin D₃ and D₂, respectively. Optimized UV-B exposure enhances vitamin D content in mushrooms, milk, bread and yeasts with minimal impact on other vitamins or sensory properties. Recent meta-analyses and dose-response studies confirm that vitamin D₂ formation in mushrooms (e.g., Agaricus bisporus) is strongly wavelength-dependent, with peak efficiency in the UV-B range; optimized parameters (e.g., ~16,664 J/m² at 3.2 W/m² for sliced mushrooms) yield up to 16 to 20 μg/g D₂.
Commercial-scale applications include pulsed light systems (broadband, high-intensity pulses containing UV-B) used by several mushroom producers to achieve consistent vitamin D₂ enrichment while preserving quality. Interestingly, the lamps are not filtered, allowing unwanted wavelengths to impinge on the food, opening the door to the use of narrow-line-width UV-B LED systems, which are approaching commercial feasibility for mushrooms and milk.
International Regulations
Regulatory frameworks increasingly recognize UV as a safe, controllable technology for nutritional modification when validated.
United States
The Food & Drug Administration (FDA) approves UV treatment for vitamin D enhancement via photoconversion. 21 CFR § 172.382 authorizes vitamin D₂ mushroom powder as a food source of vitamin D₂ when produced by exposing aqueous homogenates of Agaricus bisporus to UV light (total dose ≤12 J/cm²), with no changes to this regulation as of 2026. 3
European Union
UV-treated foods are regulated under food additives, processing aids and novel food rules, Regulation (EU) 2015/2283. In 2024, EFSA 4 issued a positive safety opinion on UV-treated Agaricus bisporus mushroom powder with elevated vitamin D₂, concluding it is safe for use in foods and supplements under proposed conditions. Earlier opinions supported UV-treated milk/milk products (vitamin D₃), bread and baker’s yeast (vitamin D₂). In 2025, Commission Implementing Regulation (EU) 2025/691 authorized vitamin D₂ mushroom powder on the market.
In the UK (retained EU law), the Food Standards Agency and Food Standards Scotland completed a 2024 safety assessment extending the conditions of use for UV-treated baker’s yeast to additional categories, including water-based beverages.
Canada and Other Jurisdictions
Health Canada permits UV-treated mushrooms as supplemented foods. Similar approvals exist in Australia and New Zealand under FSANZ standards.
Implications for Industry
Strategic selection of UV wavelength, dose and exposure transforms UV from a purely germicidal technology into a versatile, functional processing tool. It enables minimization of vitamin degradation, targeted photoconversion for nutritional enhancement and precise enzymatic control to reduce browning and oxidation. The current equipment form is the first-generation conveyor-type system. In the future, more tailored designs with associated UV monitoring for quality assurance will emerge to optimize cost and throughput.
International regulatory approvals confirm that, when properly validated, UV processing is safe, effective and label-friendly beyond microbial inactivation and surface disinfection, and for water or juice treatment.
It supports advanced applications in food safety, quality and shelf-life management (e.g., enzymatic browning), and nutrition enhancement, providing manufacturers with a competitive edge in clean-label, nonthermal product development.
References
- Pihen, C., López-Malo, A. & Ramírez-Corona, N. (2024). Effect of UV LED and Pulsed Light Treatments on Polyphenol Oxidase Activity and Escherichia coli Inactivation in Apple Juice. Journal of Agricultural and Food Chemistry 72(25). https://doi.org/10.1021/acs.jafc.3c08888
- Sun, W., Jing, Z., Zhao, Z., Yin, R., Santoro, D., Mao, T., & Lu, Z. (2023). Dose–response behavior of pathogens and surrogate microorganisms across the ultraviolet-c spectrum: Inactivation efficiencies, action spectra, and mechanisms. Environmental Science & Technology, 57(29), 10891–10900. https://doi.org/10.1021/acs.est.3c00518
- U.S. Food and Drug Administration. (2024). 21 CFR § 172.382 – Vitamin D2 mushroom powder. Government Publishing Office.
- European Commission. (2025). Commission Implementing Regulation (EU) 2025/691 authorizing the placing on the market of UV-treated mushroom powder as a novel food. Official Journal of the European Union.