But in 1956, Arthur Anderson at the Oregon Agricultural Experiential Station in Corvallis could isolate radiation-resistant Deinococcus radiodurans from radiation processed ground meat. Actually radiation processed ground meat could select these resistant microbes since there is no competition. It is the most radiation-resistant vegetative form of bacteria that could withstand the radiation dose of 1.5 million rads. Similarly, refrigeration culture of storing meat in Europe resulted in the control of the Salmonella, but psychrophilic pathogen namely Campylobacter has emerged and still remains major pathogen in food. Recently E Coli O157:H7 has emerged and still remains a major pathogen in beef, causing bloody diarrhoea and renal failure. They were also found in alfalfa sprouts, unpasteurised lettuce, cheese and curd. Listeria monocytogenes has been isolated from soft cheese and processed meat in cases of food-borne infection.
Careful monitoring
There are many causes for these new food-borne infections through processed foods. As new technologies developed for food processing, new diseases emerged. Our futuristic technologies like minimally processed foods by hurdle technology, non-thermal processing of foods, storage methodologies need to be rigorously checked for microbiological safety. Microbes used in genetically-modified foods need to be monitored in processed foods carefully.
Other threats are globalisation of food supply, global travel, natural disaster, refugees, immigrants etc. Changes in microbial population, drug resistance, ability to survive in extreme environments of microbes are the challenges of the future. Increase in susceptible populations like old age, HIV infection, and poor nutritional status of the population adds to the outbreak of food-borne infections. The future threats should be tackled by the government, food industries, consumer food technologists and food microbiologists.
Update of knowledge
An update of the scientific knowledge on the irradiation of the food classes/commodities to be considered is provided, including a review of the efficacy of irradiation. However, it is stated that these food classes/commodities do not represent, at this time, a systematic classification of foods with respect to irradiation practices and that therefore the categorisation of foods to assess the efficacy of irradiation to inactivate pathogens is not necessary. In addition, the food marketing practices and consumption patterns have changed in recent years and the previous classification did not identify all foods representing a potential high risk for consumers including some ready-to-eat foods.
Range of purposes
Food irradiation has been proposed for a large range of purposes. Potential microbiological risks linked to food irradiation, such as the development of resistance, the possibility that irradiation might be used to mask unhygienic food production practices, etc.
The experts considered evidence that foods of similar composition show similar microbiological responses when similarly irradiated, thus supporting the validity of granting broadly-based generic approvals of high-dose irradiated foods.
High-dose irradiation
The chemical safety and nutritional aspects of irradiation evaluated covered vegetative bacterial cells, animal parasites, yeasts, mould propagules, bacterial spores, viruses, and preformed microbial toxins. On the basis of this exhaustive review, the report concluded that high-dose irradiation is no different from thermal processing in producing shelf-stable, microbiologically safe foods. Modern food safety management systems rely on a farm to fork approach and involve a range of actions at each step of the food chain. Measures to control biological hazards in the food chain are primarily preventive measures, to avoid contamination with food-borne pathogens. Methods relying on destruction of micro-organisms that could have contaminated the food are only additional control measures. The extent of destruction of pathogenic microorganisms in foods needed to reduce the incidence of food-borne diseases depends on many factors.
Technologies
Different technologies are currently available and used for the irradiation of food which cover gamma rays, X-rays generated from machine sources and electron beams.
None of these kinds of ionising radiation, when used for food irradiation purposes at the doses established by Codex standard have energy levels sufficient to induce radioactivity in the irradiated food. Even if the ionising radiation used is different, the different ionising radiations have the same effects on microorganisms, although some studies found e-beams slightly more efficient than gamma rays for the inactivation of bacteria in meat. For consideration of penetrability of ionising radiation, water serves as a sufficiently good model for what occurs with high moisture foods.
The irradiation dose received by food is not homogeneous because of the limits in penetration capacity of ionising radiations. This can reduce the overall efficacy of the treatment and the minimal dose received must be considered for implementation of food irradiation in practice.
Reasons
The main reason for the use of food irradiation is the ability of ionising radiation to inactivate, to varying extents, populations of microorganisms, including pathogenic bacteria, parasites and viruses.
Inactivation of microorganisms is due to damage to critical elements of the cell, often the genetic material, which can be lethal or prevent multiplication of the cell. The interaction between the ionising radiation and the genetic material can be direct, with radiation causing breaks in one or both DNA strands.
The radiation dose used in food processing is determined by the type of food being processed and the desired effects. Main purposes of food irradiation are for inhibition of sprouting of stored tubers, roots and bulbs, prevention of post-harvest losses by destruction of insects in stored cereals, fresh and dried fruits, nuts, oilseeds and pulses, or phytosanitary (quarantine) treatment for insect pests infesting fresh fruits and vegetables, delay of ripening of fruits, shelf-life extension of fruit and vegetables, meat, poultry, fish and ready meals by reduction of micro-organisms that cause spoilage among others.
