A beverage manufacturer in Kurgan was experiencing mold growth on bottle caps and secondary packaging. The problem was concentrated around the packaging and storage areas rather than inside the beverage itself.
The production line included bottle blowing, filling, capping, grouping bottles into packs of six, and wrapping them in stretch film. The total volume of the production premises was approximately 1,200 m³.
The plant needed a system that could reduce airborne contamination and treat accessible packaging surfaces without requiring major modifications to the existing filling line.
The Condensation Problem
The beverages left the filling process at a temperature of approximately +2 °C and then entered a warmer production area. The temperature difference caused moisture from the surrounding air to condense on the bottles and caps.
After the bottles were grouped and wrapped in stretch film, some of this moisture remained trapped inside the package. Restricted air circulation slowed evaporation and created favourable conditions for mold spores that had settled on the wet surfaces.
The contamination risk was therefore created by several connected factors:
cold bottles entering a warmer room;
elevated humidity in the packaging area;
condensation on caps and bottle surfaces;
airborne mold spores;
moisture trapped beneath stretch film;
storage time before shipment.
UVC treatment could reduce the microbial load, but it could not remove the moisture itself. Condensation control therefore remained an important part of the overall solution.
Why Air Recirculators Were Not Enough
The plant already considered air-treatment equipment, but recirculators could not completely address the problem.
A recirculator treats the air that passes through its enclosed chamber. It can reduce airborne microbial contamination, but its effect on bottle caps and packaging surfaces is indirect. Once spores have settled on a surface, that surface must receive a sufficient UVC dose directly.
UVC radiation also cannot reliably penetrate opaque packaging or reach areas hidden beneath stretch film. This meant that local surface treatment had to take place before the bottles were grouped and wrapped.
The project was therefore divided into two treatment stages:
reducing the general microbial load in the production environment;
irradiating accessible surfaces directly on the conveyor.
Stage One: Treatment of the Production Area
The first stage involved the installation of UVL-Aero 100 open UVC irradiators in the main production area.
Open irradiators act on both room air and exposed surfaces. However, direct short-wave UVC radiation is hazardous to the eyes and skin. Such equipment must therefore operate according to an approved safety procedure—typically when personnel are absent—or be combined with shielding, warning indicators, timers, access control, and interlocks.
The UVL-Aero 100 and UVL-Aero Prof 75 units use AISI 304 stainless-steel housings. Antishatter lamp protection was selected for the food-production environment to reduce the risk associated with accidental lamp damage.
This stage was intended to lower the background microbial load in the production area. It did not replace scheduled cleaning, ventilation, or humidity control.
Stage Two: Direct Treatment on the Conveyor
The second stage used a compact VOZUF 444 mm conveyor irradiator.
The unit was installed at a point where the target surfaces were still open and accessible. This allowed UVC radiation to act on bottle or cap surfaces before grouping and stretch wrapping created shaded areas.
The installation parameters were:
irradiator length: 490 mm;
conveyor width: 40 mm;
available mounting section: approximately 350 mm;
line capacity: up to 3,000 bottles per hour;
remote electronic ballast: L-220-1×200-2201-15;
ballast connection cable: 10 m;
quartz sleeve and sealed lamp assembly.
The quartz sleeve and sealed connection assembly protected the lamp components from moisture and cleaning chemicals. The electronic ballast was installed remotely, outside the immediate wet zone.
Matching UVC Exposure to Conveyor Speed
The number of bottles processed per hour does not by itself determine the received UVC dose. The result also depends on conveyor speed, effective irradiation length, distance from the lamp, and irradiance at the target surface.
The approximate exposure time can be estimated as:
[
t = \frac{L}{v}
]
where:
(t) is the exposure time;
(L) is the effective irradiated length;
(v) is the conveyor speed.
The surface dose can then be estimated as:
[
D = E_{\text{avg}} \times t
]
where:
(D) is the UVC dose;
(E_{\text{avg}}) is the average irradiance received by the surface.
In practice, the minimum dose across the target area is particularly important. Caps, bottle shoulders, guides, neighbouring products, and mechanical elements can create shadows.
For that reason, irradiance should be measured at product level and at the least-exposed points—not only directly beneath the centre of the lamp.
Implementation
The project was completed in two stages. The UVL-Aero equipment was installed first to address environmental contamination. The conveyor irradiator was introduced afterwards to treat accessible surfaces at the critical point of the packaging process.
This staged approach allowed the plant to improve microbiological control without rebuilding the entire filling and packaging line.
The final system provided:
lower airborne microbial contamination in the treated areas;
direct UVC treatment of accessible bottle and cap surfaces before secondary packaging;
reduced risk of mold growth on packaging during storage;
moisture-resistant equipment for the conveyor area;
remote placement of the electronic ballast outside the wet zone;
less dependence on repeated manual surface treatment;
lower potential losses associated with damaged packaging and rejected products.
UVC Is Only Part of the Solution
UVC treatment reduces viable microorganisms only where sufficient radiation reaches the target. It does not dry the bottles or prevent new condensation from forming.
For stable long-term results, the plant should also control:
temperature differences between the beverage and packaging area;
relative humidity near the line;
ventilation and filtered air supply;
drying time before stretch wrapping;
cleanliness of conveyor components;
condition of the quartz sleeve and reflector;
lamp operating hours and output;
microbiological results during storage.
The effect of the system should be verified using surface swabs, airborne microbial sampling, and comparative storage tests. Visual absence of mold alone is not sufficient to quantify the effectiveness of treatment.
Conclusion
Mold on PET beverage packaging can develop when cold bottles enter a warm, humid environment and are wrapped before the condensate has evaporated.
In this project, the problem was addressed with two complementary UVC stages: room-level treatment to reduce environmental contamination and local conveyor treatment of accessible surfaces before stretch wrapping.
This approach does not replace sanitation or condensation control. It adds a targeted microbial barrier at the stages where contamination is most likely to affect the finished package.
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