Using Radiation for Sanitization in Dairy Processing

In dairy processing, keeping surfaces and packaging free from harmful microorganisms is a non-negotiable requirement. While heat and chemical sanitizers have long been the standard tools for this job, they are not always viable – some equipment contains heat-sensitive components, and chemical residues can compromise product quality. This is where radiation-based sanitization, particularly ultraviolet (UV) light, steps in as a practical, chemical-free alternative. It is classified as a non-conventional sanitizer, used specifically in situations where conventional methods are either unsuitable or carry unacceptable risks.

What is radiation sanitization? 🔗

Radiation sanitization uses electromagnetic energy to destroy or inactivate microorganisms on surfaces, equipment, and packaging materials. Unlike heat or chemical methods, radiation works by directly damaging the DNA and cellular structures of pathogens – bacteria, viruses, fungi, yeasts, and molds – without requiring physical contact or leaving any residue behind. In dairy facilities, this makes it particularly valuable where contamination risk is high but conventional sanitization methods are not feasible.

The main types of radiation used in food and dairy processing contexts are ultraviolet (UV) light, gamma rays, and electron beams (e-beam). Each works on the same fundamental principle – disrupting microbial genetic material – but differs in energy level, penetration depth, and application.

UV radiation: the primary tool for surface sanitization 🔗

Among all radiation types, UV light is the most widely used for sanitizing surfaces in dairy plants. UV light occupies the portion of the electromagnetic spectrum between visible light and X-rays, spanning wavelengths from 100 to 400 nm, and is classified as a non-ionizing form of radiation. It is divided into four sub-bands: UV-A (315-400 nm), UV-B (280-315 nm), UV-C (200-280 nm), and vacuum-UV (100-200 nm).

Of these, UV-C is the one that matters most for sanitization. UV-C has the most effective germicidal effect on microorganisms including bacteria, viruses, protozoa, fungi, and algae, with maximum germicidal effect observed at a wavelength of approximately 253.7 nm.

How UV-C destroys microorganisms 🔗

When UV-C light strikes a microbial cell, it is absorbed by the cell’s nucleic acids – specifically DNA and RNA. This triggers photochemical reactions with the thymine constituent of the cell’s DNA/RNA, producing thymine dimers – abnormal chemical bonds that arrest cellular metabolism and prevent further multiplication. The result is that the microorganism can no longer replicate, even if it is not immediately destroyed.

This process is fast. UV light at 254 nm destroys the DNA of all microorganisms so that viruses, bacteria, yeasts, and fungi are rendered inactive in seconds. Importantly, unlike chemical sanitizers, microorganisms do not develop resistance to UV radiation over time, which is a significant practical advantage in a dairy facility running continuous production cycles.

Applications in dairy plants 🔗

UV radiation is applied across several critical points in dairy processing, all of which share a common characteristic: they involve surfaces or materials that either cannot tolerate heat or must remain free of chemical residues.

Equipment surfaces and conveyors 🔗

Conveyor belts, filling machines, and other equipment surfaces are regular targets for UV sanitization. UV light can be used to disinfect surfaces of conveyors and other equipment in preparation, production, and storage areas, but microorganisms must be exposed to UV light directly, with no obstruction between the UV source and the target surface. UV lamps installed above and alongside conveyor belts provide continuous decontamination during processing, reducing the number of full washdowns needed and thereby saving water and energy.

Packaging materials 🔗

One of the most important applications of UV sanitization in dairy processing is the treatment of packaging materials before filling. Bottles, tubs, foils, films, cartons, lids, and closures all accumulate microbial contamination during manufacturing and handling. Spoilage microorganisms are removed by UV irradiation of surfaces prior to filling, which increases shelf life and lowers the risk of contamination.

In the dairy industry, UV disinfection is used especially for the packaging of fresh milk products such as yoghurt, cream cheese, and dips that are kept in the cool chain, in order to improve shelf life – meaning the dairy processor receives significantly fewer returns of spoiled product.

Heat-sensitive equipment components 🔗

Certain dairy processing equipment contains electronic components, rubber seals, plastic parts, or precision instruments that cannot withstand the temperatures required for heat sanitization. UV radiation offers a practical solution here – it sanitizes these surfaces without raising their temperature, preserving the integrity of sensitive components while still meeting hygiene requirements.

Air sanitization in processing areas 🔗

Beyond surfaces, UV light is also used for air disinfection in dairy facilities. Wall-mounted or overhead UV fixtures create a zone of germicidal radiation in processing and packaging areas, continuously reducing airborne microbial loads. This is especially important in facilities where post-pasteurization contamination from the surrounding environment poses a risk.

Gamma radiation and electron beams in dairy contexts 🔗

While UV radiation handles surface and packaging sanitization within the plant, gamma rays and electron beams (e-beam) represent higher-energy ionizing radiation technologies used for more intensive decontamination tasks, particularly for pre-sterilizing packaging materials before they enter the filling line.

Packaging materials are commonly irradiated prior to filling by companies in the dairy industry – for products such as cream, butter, and eggnog – as well as in processed food, beverage, pharmaceutical, and medical device industries.

Gamma radiation is generated by radioactive isotopes such as cobalt-60 and cesium-137, while electron beam (eBeam) technology uses industrial electron accelerators and can be switched on and off as needed – a significant operational advantage over continuous gamma sources. Low-energy e-beam applications include surface sterilization, aseptic packaging, and food packaging modifications.

E-beam technology can sterilize packaging materials prior to filling, ensuring they do not introduce contaminants to the food – which is particularly important for ready-to-eat products. Unlike gamma irradiation, e-beam processing does not involve radioactive materials, making facility management and regulatory compliance more straightforward.

Why radiation sanitization is used instead of chemical or thermal methods 🔗

The core reason radiation sanitization exists as a category is that conventional methods have real limitations in specific scenarios. Chemical sanitizers, while effective, leave residues that can contaminate dairy products, alter flavor, or create compliance challenges. Thermal methods are destructive to heat-sensitive materials and require extensive downtime for heating and cooling cycles.

Radiation sanitization addresses both problems simultaneously. UV-C offers technological advantages including low maintenance and installation costs, minimal energy use, and food preservation without undesirable effects of heat treatments. There are no chemical residues, no temperature stress on equipment, and the action is near-instantaneous. UV light is a dry and biologically inert process that can reduce microorganism counts by around 99.9% with minimal heating of packaging material.

Factors affecting UV sanitization effectiveness 🔗

UV radiation is not equally effective in all conditions. Several factors determine how well it works in practice.

Surface cleanliness 🔗

UV light can only sanitize what it directly reaches. Since dirt absorbs radiation and thereby protects bacteria, UV light must be applied after the cleaning process – the success of UV sanitization depends on the cleanliness of the material surfaces. Grease, protein residues, or biofilm deposits will shield microorganisms from exposure and significantly reduce effectiveness.

Surface texture and geometry 🔗

Smooth, non-porous, reflective materials such as polished stainless steel and borosilicate glass demonstrate superior performance by maximizing UV penetration and minimizing shadowing effects, whereas rough, porous, or fibrous surfaces reduce penetration and create shadowing that limits microbial inactivation.

Distance and exposure time 🔗

The intensity of UV light decreases rapidly with distance. UV-C intensity follows the inverse square law – doubling the distance from the source reduces intensity by a factor of four. Different microorganisms also require different UV doses. UV-C exposure levels used in sanitizing food manufacturing operations range from 10 to 100 mJ/cm². Bacteria such as Salmonella, Listeria, and E. coli are relatively easy to inactivate, while thick-walled mold spores require significantly higher doses.

Biofilm formation 🔗

Biofilm formation is one of the most important challenges in dairy plants – biofilms block light transmission and act as a protective barrier for microorganisms against UV light, significantly reducing treatment efficacy. This reinforces the importance of thorough cleaning before any UV sanitization step is carried out.

Limitations and safety considerations 🔗

Despite its advantages, UV radiation has clear constraints that must be acknowledged when designing a sanitization program.

The most fundamental limitation is the line-of-sight requirement. UV light only sanitizes surfaces it directly reaches – any shadowed areas, crevices, or hidden surfaces will not receive adequate treatment. This is why UV sanitization works best on open, smooth surfaces rather than complex equipment with recessed cavities.

UV light also has limited penetration depth. It sanitizes surfaces and very thin films, but cannot penetrate deeply into materials or treat thick liquid layers. For opaque liquids like milk, UV light has a restricted penetrability – transparent fluids such as water are effectively disinfected, whereas opaque fluids such as milk are affected less due to the poor penetration depth of light.

Worker safety is another important factor. Direct exposure to UV-C radiation causes severe skin burns and eye damage within minutes. Any UV sanitization installation in a dairy plant must include proper shielding, interlocks, and safety protocols to ensure workers are never exposed to direct UV-C light during operation.

Finally, it is worth noting that UV light does not replace pasteurization, which uses heat – it is a complementary technology, not a substitute for established thermal processes. It is most effective as part of a broader hygiene program that combines cleaning, thermal treatment where applicable, and UV sanitization for targeted applications.

Regulatory status 🔗

UV-based sanitization in dairy processing has gained regulatory acceptance in several key markets. The European Food Safety Authority (EFSA) concluded that UV-treated milk is safe under the intended conditions of use, and UV-treated pasteurized cow’s milk has been authorized as a novel food by the European Commission. In North America, Health Canada and the FDA have frameworks governing UV treatment of food products and packaging.

What do you think? Given that UV radiation leaves no chemical residues and works in seconds, should it become a standard requirement for packaging sanitization in all dairy facilities – or does its line-of-sight limitation make it too unreliable to depend on without a chemical backup? And as consumer demand for cleaner labels and additive-free dairy products grows, how do you see non-conventional sanitization methods like radiation shaping the future of dairy plant hygiene?

References

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