Gamma and electron beam for nutrients and bioactives conservation in chestnuts, mushrooms, and dry plants

Preservation of food is a permanent defying target due to the continuous growth of population, scarcity of soil, and health food safety aspects. Different processing technologies are currently used to preserve food; irradiation processing based on the use of ionizing radiation is used to extend the shelf life of the products, that is, stopping the maturation process; decontamination, that is, lowering the presence of bacteria and fungi; or sterilization of food products, that is, eliminating all the microorganisms. This process is also called “cold pasteurization,” as it does not increase the temperature of the irradiated products significantly. By using this technology, food components that are particularly sensitive to thermal treatments, like aromatic compounds in medicinal or edible plants, could be decontaminated. Currently, three types of ionizing radiation are authorized for food irradiation processing: gamma radiation, electron beam (e-beam), and x-rays (E.U., 1999a). Gamma radiation comes from the spontaneous emission of the isotopes of cobalt-60 (Co-60) or Cs-137; e-beam radiation is produced by accelerating electrons till the energy of 10 MeV (mega electron volt); and x-rays are produced by the impact of accelerated electrons on a metallic target, with the consequent emission of radiation (photons), by a physical phenomenon described as “bremsstrahlung.” The three types of radiation have different characteristics, namely the depth of penetration, but all can be used for food processing using the right configuration adapted to the type or volume of food to be processed. X-rays were the first ionizing radiation tested for food preservation; however, due to the low efficiency of conversion of electrons energy to x-rays only recently, with the development of new machines, this technique regained interest. Recently, food irradiation has been pushed by phytosanitary trade barriers, to eliminate the presence of insects, or due to health issues with contaminated food, for example, Salmonella or Listeria, demanding new approaches to guarantee food safety, without compromising the quality of the processed product (Cabo Verde et al., 2010; Antonio et al., 2013). Ionizing radiation processing is an alternative to chemical fumigation that is harmful for the environment as well as the operators and leaves residues in the products. This technology is also particularly important in the preservation of aromatic compounds in edible and medicinal plants that are particularly sensitive to other decontamination processes, for example, vapor steam sterilization, due to its thermal sensitivity. However, as in other food processing methods, irradiation may preserve some components and degrade others. The balance of advantages and disadvantages, in comparison to other preserving processes, should be used to select or not this type of processing technology, to provide to the consumer a product that fulfills the best criteria of quality and safety.