Radiation for food preservation

Print edition : August 29, 2003

FOOD irradiation, one of the beneficial applications of atomic energy, is an important innovation in food preservation since the development of canning in the 19th century. It provides an effective alternative to fumigants, which are being phased out owing to their adverse effects on the environment and human health. Moreover, exposure of food material to radiation has strong advantages over conventional methods of preservation such as cold storage, fumigation, salting and drying because it does not lead to loss of flavour, odour, texture or quality.

Swapnesh Kumar Malhotra, Head of the Public Awareness Division, Department of Atomic Energy (DAE), says: "Radiation technology can complement existing technologies to ensure food security and safety." He said radiation processing could be used for anti-infestation of foodgrains and pulses; inhibition of sprouting in onions, potatoes, garlic, yam and ginger; preventing microbial contamination of spices; extending shelf-life under recommended conditions of storage; and overcoming quarantine barriers in international trade. The technology can be used for sterilising cut-flowers, pet food, cattlefeed, aquafeed, ayurvedic herbs and medicines, and packaging material.

India is one of the few countries that have the expertise in the deployment of radiation technology. The process involves the controlled application of energy of ionising radiation such as gamma rays, X-rays and accelerated electrons. Irradiation is a direct, simple and efficient one-time process. Application of low doses of radiation (0.15 kilo Gray) can arrest the sprouting of potatoes and onions. (Gray is the unit of absorbed radiation energy.) As a result, storage losses of tubers and bulbs due to sprouting, and their dehydration can be reduced substantially.

Low-dose applications (less than one kGy) also lead to the disinfestation of insects in stored grain, pulses and food products, and the destruction of parasites in meat and meat products. A medium dose (one to ten kGy) eliminates microbes in fresh fruits, meat and poultry products, destroys food pathogens in meat, and helps in the hygienisation of spices and herbs. A high dose (above 10 kGy) produces shelf-stable foods without resort to refrigeration, and the sterilisation of food for special requirements.

The irradiation process has been approved by the Food and Agriculture Organisation (FAO), the World Health Organisation (WHO), the International Atomic Energy Agency (IAEA) and the Codex Alimentarius Commission. About 100 countries have approved the process for application in more than 100 items of food. India first approved them in 1994. Today, the Directorate of General Health Service, under the Prevention of Food Adulteration Act, has approved more than 20 commodities to be processed using this method. Food irradiation is done in plants approved by the Atomic Energy Regulatory Board (AERB), and local food and drug administrations.

THE DAE has set up two technology demonstration facilities for irradiating food, agricultural and other products. One is at Vashi, Navi Mumbai, for the application of high doses for spices and dry vegetables. Another is at Lasalgaon, near Nashik, for onions, cereals, pulses and their products and cut-flowers, which require low doses.

Malhotra said entrepreneurs in private and cooperative sectors have shown interest in setting up radiation processing plants. A women's non-governmental organisation, Annapurna Mahila Mandal, is selling radiation-processed spices in and around Mumbai. Malhotra said: "There is a need to deploy and integrate this technology with the national system of procurement, storage, distribution and marketing of agro-produce. Radiation processing plants designed to process several products requiring a specified range of radiation doses need to be set up in private, cooperative and public sectors."

The Food Irradiation and Processing Laboratory of the Bhabha Atomic Research Centre (BARC) is one of the foremost laboratories of its kind in the world. Irradiation techniques developed at this centre have been effective in arresting sprouting in onions and potatoes; delaying the ripening of fruits such as bananas, mangoes and papayas; disinfesting grains; extending the shelf-life of fish and meat; eliminating pathogens from frozen seafood; and preventing microbial and insect contamination of spices.

India is the largest producer of onions in the world. Onion is planted during winter (rabi crop) in most parts of the country and harvested during April-May. More than 1.5 lakh tonnes of onion is stored in Nashik district from June to October in conventional chawls. In Nashik, low ambient temperatures and high humidity conditions during the rainy season, beginning from July, lead to the sprouting of onions. Similarly, the sprouting of stored onions occurs following the rainy season in Mahuwa, a major onion production and storage centre in Bhavnagar district of Gujarat. Sprouted onions shrivel faster owing to increased water loss by transpiration. But irradiation at very low dose levels inhibits sprouting in onions. The DAE says that the process consists of exposing onions to gamma rays in a shielded room for a specified duration. The onions are brought into and taken out of the room by conveyors or carriers.

According to the DAE, gamma irradiation is the answer to problems of producers and exporters of spices. Since gamma rays have high penetrating power, spices can be irradiated after packaging, irrespective of the size of the carton. This ensures that there is no contamination at the time of the opening of the package.