Fundamentals of UV sterilization for foodDerek Johnson | July 28, 2021
Microorganisms are responsible for the largest percentage of food loss in the food and beverage industry today.
Although they play an important role in food production (for example, yeasts, molds and bacteria are useful in making food products such as bread, beer, wine, vinegar, yogurt, amongst others), the growth and activity of pathogenic microorganisms cause food spoilage and contamination. This type of damage badly affects the food and beverage industry in terms of economic loss, reputation damage and punishment by local law.
But why is it that most food companies can’t seem to find a solution?
Most likely, adhering to strict food safety and quality regulations, such as the U.S. Food and Drug Administration (FDA) and the FDA Food Safety Modernization Act (FSMA), is an expensive and time-consuming effort. The FSMA safety plan consists of five steps:
- Hazard analysis
- Preventive control
- Oversight of preventive control
- Supply chain program
- Recall plan.
That said, ultraviolet (UV) sterilization has evolved into one of the safest and cost-effective ways of mitigating microorganisms such as bacteria and mold. While it has also found applications in various industries, this article focuses on everything you need to know about UV sterilization in the food and beverage industry.
What is UV sterilization?
Firstly, UV stands for ultraviolet light. Therefore, UV sterilization in the food industry refers to the use of ultraviolet energy to improve the safety and extend the shelf life of food produce and end products by delaying microbial growth and preventing the activity of pathogenic microorganisms. This term is also referred to as food irradiation. However, the UV sterilization process does not add radiation to its subjects in any way.
But, what is UV light/energy?
It is a form of electronic radiation characterized by light emissions with wavelengths shorter than visible light but longer than that of the X-ray. There are different sources of UV light; however, the sun is the only natural source. The sun is made up of 3% UV rays and in that small portion are different types of UV rays.
Depending on the wavelength, UV rays can be divided into three main types, namely:
● UVA (320 nm to 400 nm)
● UVB (280 nm to 320 nm)
● UVC (100 nm to 280 nm)
The UVC range, specifically 254 nm, is referred to in the food industry and beverage industry, as Germicidal Ultraviolet Light (GUV). This is the range most lethal to microorganisms, including yeast, bacteria and mold. Here, UV breaks the molecular bonds in the DNA of its targets, destroying their ability to reproduce and ultimately killing them.
That said, there are different UV doses (intensity and duration of exposure) depending on the cell structure of the microorganisms of interest. For example, salmonella, listeria and E. coli have thin cell walls and are therefore easily susceptible to UV rays. On the other hand, molds have relatively thick cell walls and require high-intensity UV radiation to destroy.
UV sterilization is not a new concept and has since found numerous applications in various industries, including different sectors of the food and beverage industry.
What are the applications in the food and beverage industry?
Although UV rays are an effective method for eliminating microorganisms, it is not advisable to directly irradiate food produce or end products because it can result in discoloration and the development of off-flavors. That’s why the application of UV sterilization in the food and beverage industry is divided into three categories:
● Surface disinfection
● Air disinfection
● Liquids disinfection
This includes the sterilization of all the surfaces in contact with food products. This ranges from packaging materials, such as containers, wrappers, bottle caps, and conveyor belts. Surface disinfection is particularly useful in meat processing facilities. Here, UV light is used to continuously decontaminate conveyor belts through a watertight module that ensures the belt is exposed to UV light as it passes.
The GUV radiation acts on microorganisms on the conveyor belt’s surface to render them inactive. This treatment is proven to reduce water and energy costs as the need for numerous complete washdowns during processing is significantly reduced.
There are numerous other applications under this heading. One of which is in the dairy industry to sterilize packaging materials of fresh milk products, for example, yogurt.
UV radiation is also useful in disinfecting the food environment. Most food and beverage companies utilize a system for sensitive foodstuffs that combines a filter barrier through which air must pass before reaching food products and a UV radiation set up to kill any surviving microorganisms.
Additionally, UV rays have applications in the fruit and vegetable sector. For high-quality mechanically peeled fruits and vegetables, UV-treated air is often blown through the peeling unit.
This is one of the most common applications of UV sterilization. UVC rays are often used in water production companies to eliminate a wide range of microorganisms. Similarly, combining UVC with ozone results in powerful oxidation of water, hence, significantly reducing its organic content.
What are the advantages and disadvantages of UV Sterilization?
● UV sterilization is environment-friendly as it reduces the use of chemicals.
● Reduces water and energy cost.
● Reduces storage cost as it eliminates the need for specialized storage equipment.
● UV sterilization is an effective method for killing microorganisms. Studies show a 99.99% efficiency in sterilizing water.
● It is economical. In other words, it is cheap and with a long lifespan.
● UV sterilization requires that light reaches its subject. Therefore it is ineffective when an external object blocks its path.
● It can result in some painful damage to human eyes and skin.
What lighting and electrical technologies are prevalent?
Low and medium pressure mercury
This is the most practical way to generate GUV radiation. Low-pressure mercury lamps have the same shape, electric connection and operating power as a standard fluorescent lamp without coating. Medium pressure mercury is useful, particularly in water disinfection. However, at 254 nm, its efficiency is ironically lower, but with a higher power per unit length.
Light-emitting diodes (LEDs)
LEDs are emerging UV technologies and despite low efficacies are becoming more available. However, questions about the ability to compete with its mercury counterparts hover above its existence. Current uses for UV LED are within wavelengths of 265 nm, 273 nm, and 280 nm.
Krypton chlorine excimer lamps
Excimer lamps are becoming rampant in the market, and they offer great promise as these systems can produce specific wavelengths (205 nm to 230 nm) with lower risks to the skin and eye.
Key UV specifications
Key UV specifications depend on the manufacturer and application. That said, any UV product specification must include the required reduction time and contact time. Also, UVC manufacturers must comply with all regulatory requirements, such as the Title 21 Code of Federal Regulations (CFR) Parts 1000 through 1004, and section 1005.25, and as applicable, 21 CFR Chapter I, Subchapter H.
This is all about UV sterilization in the food and beverage industry. The challenges associated with UV radiation have hampered its adoption in some food industry sectors of the food industry, but recent technological advances have led to the its rising use in food sterilization. This is likely to ramp up in the near future as manufacturers compete to build reputations as the safest and most hygienic.
About the Author
Engineer and technology enthusiast. Derek Johnson is an avid reader and a research-loving technical writer with over seven years of experience creating technical blogs, training manuals, technical support, feature articles, SOPs, amongst others.