UV disinfection: a better alternative to pasteurization?

Treating water and other liquids with UV disinfection is 600 to 10,000 X more energy-efficient than pasteurisation.

Food manufacturers want to set up their process as efficiently as possible. With maximum quality and safety, at minimum cost and energy consumption. Replacing pasteurization with UV disinfection can be an important step in this process.

What is pasteurization?

Pasteurization was invented in the 1860s by Louis Pasteur, a microbiologist and pioneer in vaccination and germ theory. People had already been disinfecting liquid food by heating it for several centuries, but Louis Pasteur developed a way of doing so without sacrificing the quality. It turned out to be a discovery that has made our food safer and longer lasting for over 150 years.

Pasteurization is different from boiling. In boiling a liquid, the temperature is raised to 100°C, while in pasteurization the temperature can be much lower. The trick is to maintain the temperature until the liquid is decontaminated. Then the liquid is quickly cooled for refrigeration. Pasteurization temperatures and times are 63-65°C for 30 minutes, or 72°C for 15 or 30 seconds, or even 135°C for 1-2 seconds.

Fig 1 - Schematic overview of pasteurization system

What is UV disinfection?

UV disinfection uses powerful UV-C light to destroy the DNA or RNA in microorganisms such as bacteria, fungi and viruses. This method is applied to drinking water, food and wastewater, as well as surfaces and air, among other things. Since UV light directly damages genetic material, it is very energy efficient. No energy is used to heat or unnecessarily treat the surrounding liquid.

Typical UV disinfection doses are 300 J/m² and 400 J/m². In some extreme cases such as horticulture where the pathogens can be tougher to kill the significantly higher 2500 J/m² is used.

Fig 2 - Schematic representation of DNA damage by UV-C light.

Pasteurization vs. UV disinfection: the essential difference

The major difference between pasteurization and UV disinfection is energy consumption. Pasteurization of milk consumes about 200 kWh per m³, depending on the type of process used and the efficiency of the equipment [1]. Pasteurization consumes so much energy because water (milk is almost 90% water) is a heat sink and very good at absorbing energy without raising the temperature very much. For the same reason, it takes a lot of energy to cool the milk quickly to prevent recontamination since a heat sink works the same in both directions.

UV disinfection normally uses about 0.02 kWh per m³ and in some extreme cases up to 0.3 kWh per m³. This is because it only takes light to shine on the microorganisms to kill them. All the UV-C light does is damage the genetic material directly, without the need to heat the water or milk. This means that UV disinfection is 600- 10 000 times more energy efficient than pasteurization. This is also confirmed by the literature [2].

UV disinfection is still unexplored territory

The demonstrated energy efficiency makes UV disinfection a widely used technique in the food industry. In dairy processing, however, it is still largely unexplored territory. In many cases, heating techniques such as pasteurization are even mandatory. Currently, there are too few research results to determine the effectiveness of UV disinfection for milk, for example.

Conclusion

UV disinfection, like pasteurization, is a well-known, tested and chemical-free method for disinfecting food. UV disinfection even does this at minimal cost and energy, with a very high safetylevel. As a result, UV disinfection seems potentially a valuable alternative to pasteurization. However, additional research is needed to prove this. Therefore, it is important that UV technology companies and food manufacturers investigate the effectiveness of UV disinfection for various dairy products in the near future.

References

1. A. Modi, R. Prajapat; “Pasteurization Process Energy Optimization For A Milk Dairy Plant By Energy Audit Approach;” International Journal of Scientific & Technology Research 3(6); 2014
2. Ioanna Neokleous, Justyna Tarapata, Photis Papademas; “Nonthermal turbulent flow ultraviolet‐C (UV‐C) radiation processing for cheese whey‐brines purification;” International Journal of Dairy Technology 75(3); 2022.