Hygienic beer caps using UV LED technology

To ensure clean water for high-quality beer, brewing companies often install ultraviolet (UV) systems upstream of their brewing equipment, with the purpose of keeping the drinking water free of germs. Fraunhofer researchers are investigating a greener and more efficient alternative, which uses UV LEDs to destroy bacterial DNA. The technology is also suitable for disinfecting brewing water and for disinfecting the caps for bottled beer, soft drinks and mineral water during the filling process.

UV light is used to keep drinking water clean as it is very effective in killing bacteria, viruses and germs — their genetic material (DNA) is destroyed by the UV rays. The brewing water is disinfected by pumping it through stainless steel tubes in which UV lamps have been fitted. UV light with a wavelength of 265 nanometres is especially suitable for this task.

Until now, this UV light has been generated using mercury-vapour lamps, which emit light at 254 nanometres; but as this lies below the optimal wavelength of 265 nanometres, the disinfection performance is not optimal. A further disadvantage of this type of lamp is that mercury is a heavy metal that can damage the environment. Other disadvantages include long warm-up phases, short service lives and lack of flexibility due to their bulky design.

Researchers at the Advanced System Technology (AST) branch of the Fraunhofer Institute for Optronics, System Technologies and Image Exploitation IOSB, in collaboration with project industry partner PURION GmbH, have been investigating a solution to replace the conventional lamps containing mercury with ultraviolet light-emitting diodes (UV LEDs).

“We prefer UV LEDs, which emit at a maximum wavelength of 265 nanometres,” said Thomas Westerhoff, scientist at Fraunhofer IOSB-AST. “Of particular interest are UV-C LEDs, because their radiation destroys the DNA of the pathogens much more effectively. The UV rays generate resonances in the nucleic acids of the DNA and break the bonds of the molecules open. This changes the cell nuclei of the microorganisms in a way that renders cell division impossible. Consequently, the pathogens can no longer multiply.”

PURION managing director Mark Wipprich (left) and Fraunhofer researcher Thomas Westerhoff (right) with a UV-C LED module.© Fraunhofer IOSB-AST/Martin Käßler

The UV LEDs do not require any warm-up phase — they reach full power instantly. In addition, they offer high mechanical stability, are not toxic and can be operated at low voltage. Another advantage is that LEDs are spotlights, and by virtue of their radiation pattern, they offer a wide range of design possibilities.

Following numerous practical tests, the researchers are now able to operate the UV LEDs directly in water without the need for a tube to encase them. Thus they eliminate reflections to further increase the performance yield of the radiation sources.

Test set-up for UV-C LEDs. © Fraunhofer IOSB-AST/Martin Käßler

For the industry partner, the experts have developed a special module that can disinfect the insides of beer caps during the production process before the bottles are filled with beer. This ensures that no germs get into the bottles during the production process. “We’re able to irradiate the inner surface of the caps with a UV power of four watts. Doing that with mercury-vapour lamps on such a small surface is almost impossible,” said the engineer.

The new technology also has applications in medical devices.

Top Image credit: ©stock.adobe.com/au/W.Scott McGill