Development of Electron Beam and X Ray Applications for Food Irradiation (DEXAFI)

There is renewed interest in developing and using low energy beam devices. During this CRP a commercial company (Bühler) has developed a device (the Laatu machine) that uses a free flow system to pass dried ingredients through a beam of low energy electrons to ensure that microbiological contamination on dried products can be controlled and maintained within acceptable levels. A representative of Bühler attended the second research coordination meeting in France and made a presentation. The Laatu is being used and tested commercially. There is growing interest in the industry to use low energy electron beams in food industry settings, as is shown by the food engineering group Bühler and its in-line electron beam surface decontamination unit. At the final research coordination meeting of the CRP in 2021, participants commented that they have also noticed that there are other companies now working on low energy X ray. In the presentation on a low energy X ray irradiation unit for phytosanitary irradiation being developed in the USA (Peter Follet) it was stated that several potential end users of such a device have already been identified. There seems to be a commercial opportunity for low energy X ray irradiators. Over the period of the CRP, industry has made improved devices and new irradiation machines are now marketing. Independently from the CRP, industry has developed new sources (e.g. panel lamps) and machines (e.g. the Stellarray low energy X ray irradiator and the EXEDE low energy X ray food irradiator)

Conventional electron beam and X ray irradiation: Equipment manufactures report that there is a trend away from new 60Co (gamma) facilities and toward building new high energy electron beam and X ray irradiation facilities (new facilities built in Thailand and Australia for example). There is more interest in using machine source irradiation stimulated in some part by CRP participants providing demonstrations of electron beam and X ray irradiation (the People’s Republic of China, France-Aerial, Portugal, the Islamic Republic of Pakistan, the Kingdom of Thailand, the Socialist Republic of Viet Nam, USA). For instance, the Sichuan Institute of Atomic Energy in the People’s Republic of China worked in collaboration with the pickle industry for the electron beam irradiation of different products, Aerial in France has demonstrated that high energy X rays from a Rhodotron (FEERIX) can deliver the appropriate range of doses necessary for phytosanitary irradiation treatments using pallets of fruits. The Centre for Nuclear Sciences and Technologies (C2TN) in Portugal worked with the mushroom industry, the Nuclear Institute for Food and Agriculture (NIFA) in the Islamic Republic of Pakistan has worked with range of stakeholders to develop specific irradiated food products, the Thailand Institute of Nuclear Technology worked with small and medium sized enterprises and also won an award for developing an irradiated ginger pickle product, the Research and Development Center for Radiation Technology in the Socialist Republic of Viet Nam is working with the food and fruit industry to commercialize the irradiation of different foods.
(1) New devices were designed, built, developed and tested in China and Vietnam for use as tools to rapidly ascertain treatment parameters quickly, before conventional electron beam irradiation. These new tools can be used to quickly assess products as received by the irradiation facility and to check if it is feasible to irradiate products in a specific packing configuration. For example, dose mapping predictions help determine the most efficient means of placing product in a carrier or tote and where to place numerous dosimeters throughout the product load to measure and establish the locations of the minimum and maximum doses. The devices are in use in commercial irradiation facilities.
(2) Electron beam irradiation: Techniques were extended to low energy (<300 keV) electron beams. Research (Japan and Poland) confirmed the lethal effects of different energy electron beams on foodborne microorganisms. It was shown that low energy (200–300 keV) electrons can be as effect as high energy (7 MeV) electrons at eliminating microbial contamination from dried whole-spice samples. More work is needed to develop routine dosimetry systems but the Dµ concept could be used to determine the imparted doses to surface and near surface regions of foods. Medium energy (2 MeV) electron beam irradiation of mango fruits indicated that it can be used to preserve the fruit and extend its storage life by delaying ripening (China). Research in Portugal investigated the use of high energy (10 MeV) electron beam irradiation to provide fresh foods with enhanced nutrient or bioactive chemical components that are safe and convenient (i.e. cherry tomatoes, raspberries, and mushrooms). Research developed new ways of ensuring the hygienic quality and extend the shelf life of different types of pickled products:pickled ginger, mixed pickled vegetables, pickled shredded sweet-salted white radish, and fermented bamboo shoots. It involved working with commercial enterprises to develop electron beam-based processes that would result in irradiated products superior to their traditional counterpart and with a longer shelf-life (this work won a Thai business development prize).
(3) X ray irradiation: Research in France developed improved dosimetry systems for low (up to 300 keV) X ray irradiators. Correction factors that can be used in conjunction with Alanine / electron paramagnetic resonance dosimetry systems were established for reference, transfer and routine dosimetry. Microbial analysis and sensory survey showed that a low energy (160 keV) X ray cabinet irradiator used in hospital can ensure clean food (fresh cut vegetables) for immune-compromised hospital patients (Korea) which would improve their diet and enjoyment of food. Research also indicated that high energy X rays (7 MeV) can be tolerated by soft fruits such as strawberries at doses up to 1 kGy without significantly affecting quality and sensory properties (Korea). This paved the way for a national programme to investigate X ray irradiation as phytosanitary treatments. Research assessed the activation of induced radioactivity in food products irradiated with high energy X rays (France). After careful experimental validation (including neutron measurements) the method indicated that induced activity in food irradiated with 7 MeV X rays is not significant in comparison to natural radioactivity already present in food. Researchers developed a low energy (<200 keV) X ray irradiator for phytosanitary irradiation (USA). The X ray irradiator is being constructed in a modified standard 6m shipping container and will be capable of treating the full width of fruit boxes of various sizes used by the sweet cherry industry.
(4) Comparative Studies of Different Modes of Irradiation: Research was published on the choice of electron beam or X ray technology for a phytosanitation program (USA). Also, electron beam and gamma irradiation treatments were shown to be capable of preventing post-harvest losses due to plant pathogens affecting fruit products (Viet Nam). Phytosanitary irradiation of fresh produce indicated that dose rate effects could not be observed in wax moth and khapra beetle at two different dose rates (4 and 330 Gy/minute) applied as phytosanitary treatments (Syria). Although results of comparative studies in Egypt into electron beam, X ray and 60Co gamma ray irradiation of several plant pests seemed to indicate that there was some differences in efficacy the results for X ray irradiation may be due to dosimetry uncertainty. Comparative Studies in Pakistan indicated that electron beam, X ray and 60Co gamma ray irradiation of foods can be equally as effective, with the key parameter being delivered dose (not dose rate). These data may assist 60Co users to adopt electron beam or X ray irradiation.