Electron Beam Technology: An Acceptable Route For Food Safety

spices in a bowl. products treated using electron beam technology.
Image by Barbara Rosner from Pixabay

Food safety is paramount throughout the world. Without it we can have no confidence in what we eat if we think it might harm us. Whilst there are numerous methods available to produce and keep food safe, there are some technologies emerging such as electron beam technology that appear to offer solutions that had previously been denied food engineers and processors.

In this introduction, we will look at the characteristics of this technology.

The Nature Of Electron Beam Technology (eBeam)

Electron beam technology (eBeam) is a non-thermal food processing method that also has the benefit of being chemicals free. It has slowly but surely been making ground as a platform technology with applications not just for food safety but in other industries and applications too where thorough disinfection and sterilization is required. The pharmaceutical and medical device industries rely on this type of technology for sterilizing equipment and packaging, and making formulations safe given their stringent specifications. It is one technology  to watch!

An electron beam is a stream of high energy electrons. These can alter the chemical structures of molecules. Their power is such that they are able to modify and even destroy hazardous organic molecules and in that sense also destroy microorganisms.

Electron beams are created by radiation of a material. The energy of radiation causes electrons to be released along with gamma rays. It is also a beam made up of particles – a corpuscular ray which belongs in the same category as alpha-particle beams. Non-corpuscular electromagnetic radiation by contrast would include gamma-rays and X-rays.

Typically, the current material for gamma radiation production being irradiated is cobalt-60 or cesium-137. Unfortunately, unlike electron beam irradiation, the materials needed are radioactive which present safety issues. At least in the production of electron beams, the flow of of the beam can be turned off easily. The issue with gamma irradiation is a public one and on this basis has never been seen as a serious competitor for ebeam technology. There is plenty of stigma still attached to the use of gamma rays.

Electron beams damage the DNA and RNA chains of any foodborne pathogens as well as adulterants. the damage to a pathogen’s nucleic acids either destroys the microorganism or prevents it from being able to reproduce effectively.

An electron beam can pass through post-packaged foods and so comes into contact with pathogens which are present within penetrating distance of the electron beam. It is the only method other than fully cooking food as this too has been known for years to thoroughly cook the product. 

There are currently three domains for electron beam radiation, low energy (LEEB), medium energy (MEEB) and high energy (HEEB)  electron beams. Each has its own level of application and in due course will be discussed as this article develops.

History Of Use

The first commercial application was in 1956 and used by Ethicon on Somerville, New jersey to sterilize sutures for hospital dressings. In past times the technology was developed as part of the Strategic Defense Initiative (Star Wars) for the US Dept. of Defense in the 1980s. 

The Food and Drug Administration (FDA), U.S. Dept. of Agriculture (USDA), and World Health Organization (WHO) all approved the safety of irradiation for treatment of a wide range of foods. This includes meats, poultry, shellfish,   spices (Van Calenberg et al., 1998),  fruit, vegetables, nuts, grains, and other products.

It is approved in more than 40 countries where 1/2 million metric tons of food is irradiated every year. The global market of services for irradiation processing of foods in 2012 exceeded $2.3 billion and is projected to grow to $22.5 billion by 2030.

What Equipment Is Needed For An Electron Beam

The components of an e-beam are:-

(1) an electron gun which consists of a cathode, grid and anode. This generates and accelerates the beam.

(2) A magnetic optical system controls the way that the e-beam interacts with the material being treated. This takes the form of a magnetic focusing lens and a magnetic deflection coil.

The lens is used to control the focus of the beams and the deflection coil is used to position the beam, frequently in an oscillating manner.

A high-speed conveyor carries cartons of product to be sterilized. The e-beam machine operates as a multi-stage electron accelerator generating a dense beam of high-energy electrons that are showered across the target food, providing saturation of the target with electrons. As the food products pass through this beam, they absorb energy. Commercial e-beam accelerators emit energy ranging from 3 million electron volts to 12 million electron volts.

The advantages of e-beam sterilizition are:-

  • high dose rates
  • JIT processing
  • good processing efficiencies depending on the product
  • one product is processed at a time
  • adjustable processing rate
  • capital cost increases less rapidly with increasing capacity
  • easily controllable
  • unlike thermal pasteurisation does not produce significant degradation of bioactive compounds or sensory quality to any great degree.

The issues at the moment are:

  • low and limited penetration (Hayashi, 1991)
  • reliability because it is a complex technology
  • high capital cost because of the need for shield and an accelerator. the shied usually has to be concrete.

Commercial Developments

The technology is now a major hurdle for consideration of any HACCP plan (Hazard Analysis and Critical Control Point) 

Food irradiation using either gamma-ray or electron beams has steadily grown in the last 30 years. In the USA, there are some food plants that were using electron beams such as the one built by the Titan Corp. (San Diego, Calif. USA) now L-3 Communications back in the very late 90s. This particular plant was designed to pasteurise 400 million lbs of ground beef, plus fish, chicken, processed foods and packaged meats annually.

Spices are very suitable for this technology because of the potential to harbor high loads of microorganisms whether they are pathogenic or not. Gryczka et al., (2020) used low energy electron beams of energy between 300 keV and 10 MeV to surface decontaminate three spices; black or white pepper, and allspice. Two species survived irrqadition, Cronobacter sakazaki and Bacillus megaterium regardless of the level of the irradition.

Electron beam treatment is effective against yeast and molds responsible for spoilage and producing a short shelf-life. A dose of between 5 and 7 kGy is most effective (Mittendorfer et al., 2002).

Lower dose electron beam technology is an effective technique for extending the shelf-life by inhibiting seeds, grains and root vegetables fro sprouting or ripening. It is a very effective phytosanitary measure to protect US agriculture from invasive insects and other pests on imported vegetables and fruits.

References

Gryczka, U., Kameya, H., Kimura, K., Todoriki, S., Migdał, W., & Bułka, S. (2020). Efficacy of low energy electron beam on microbial decontamination of spices. Radiation Physics and Chemistry170, 108662 (Article).
 
Hayashi, T. (1991) Comparative effectiveness of gamma rays and electron beams in food irradiation. In: Throne S, editor. Food Irradiation. London: Elsevier Applied Sciences. pp. 169–206

Mittendorfer, J., Bierbaumer, H. P., Gratzl, F., & Kellauer, E. (2002). Decontamination of food packaging using electron beam—status and prospects. Radiation Physics and Chemistry63(3-6), pp. 833-836.

Nitzsche, R. (2020) Presentation: identifying a surrogate for electron bea inactivation of bacterial pathogens on seeds. IDT 2020 Virtual symposium. Session 110.

Van Calenberg, S., Vanhaelewyn, G., Van Cleemput, O., Callens, F., Mondelaers, W., & Huyghebaert, A. (1998). Comparison of the effect of X-ray and electron beam irradiation on some selected spices. LWT-Food Science and Technology31(3), pp. 252-258.

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