APPLICATION OF IRRADIATION IN FOOD PROCESSING INDUSTRY

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APPLICATION OF IRRADIATION IN FOOD PROCESSING INDUSTRY

ABSTRACT

Irradiation has wide range of applications in the food processing industry, and it involves the process of exposing food to controlled level of ionizing radiation. Food irradiations are also known as cold sterilization, ionizing radiation, surface pasteurization, electronic pasteurization. These are used to destroy the bacteria, parasites and inactivate the insects, molds, yeast, which is solely responsible in spoiling the majority of foods. Ionizing radiation or ionizing energy can be used to treat foods for extending the shelf life as well as improving safety and quality of foods. The irradiation process involve passing of food through radiation field allowing the food to absorb the desired amount of radiation to ionize the water molecules present in food material. The reactive molecules or free radical (H+) produced during ionization process in the foods by irradiation injures or destroy micro-organism immediately, by changing or muting the structure of cell membrane and affecting the metabolic enzyme activity. Ionizing radiations act directly on DNA, therefore the DNA will be ionized or excited causing chain of biological changes leads to cell death. The process is technical and social as it replaces the harmful chemicals and exposure of food to high temperature and pressure preservation processing techniques. This paper is focused on the application of irradiations in different products of food processing industry.

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Introduction

Irradiation is the controlled application of energy from ionizing radiations from such as gamma rays, electrons and X-rays to food and bio agricultural products for hygienization and shelf life extension. Radiation processing of foods has the potential to provide mankind with benefits as elimination of chemicals and fumigants for insect disinfestations, elimination of food borne pathogens and parasites and to provide high quality packaged food with long shelf life at room temperature 1. Microbes like Vibrio cholera, Salmonella typhymurium, Shigella.sps, and Listeria monocytogens are destroyed in foods by irradiation. The technology is being used by the Bhaba Atomic Research Centre (BARC) for inhibiting the sprouting, delay ripening, and to increase the germination rate of various agro-food commodities to maximize the productivity of cereal crops. The most recent addition to the long list of preservation techniques is the food irradiation with various application in food technology; radiation-pasteurization of spices, milk, fruits, meat, and poultry; disinfestations of grains; sprout inhibition in potatoes, onions and garlic; delay of ripening and subsequent shelf life extension of bananas, mangoes, papayas, guavas, and avocados 2. In many countries the process of low dose radiations in combination with other food preservation techniques results a great hope in accelerating the pace of progress.

Mechanism of Action

The reactive ions produces by the irradiations injure or destroy the micro-organism by changing/muting the structure of cell membrane and affects the metabolic enzyme activity. However the more important is on deoxyribonucleic acid (DNA) and ribonucleic acid in cell nuclei which are required by microorganism for growth and replication. The effect of radiation become apparent after a period of time, DNA helix fails to unwind and the micro-organism cannot reproduce by replication.

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Fig. 1: Gamma irradiator for food processing, Source: www.foodirradiationequipment.com 3

The approved sources of gamma rays for food irradiation are cobalt- 60 (the most common) and cesium-137 4. The dose (number of kGy) permitted varies according to the type of food levels as follows:

  1. Low doses - (up to 1 kGy) designed to control insects in grains, inhibit sprouting in white potatoes, control trichinae in pork, inhibit decay and control insects in fruits and vegetables.
  2. Medium doses - (1-10 kGy) designed to control Salmonella, Shigella, Campylobacter and Yersinia in meat, poultry and fish delay mold growth on strawberries and other fruits.
  3. High doses - (greater than 10 kGy) designed to kill microorganisms and insects in spices commercially sterilize foods, destroying all microorganisms thermally sterilized 5 of public health concern
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Application of Irradiation in Food Processing

Reduction of Pathogenic Microorganisms

Escherichia coli O157:H7, Salmonella, Campylobacter jejuni, Listeria monocytogenes, and Vibrio are of primary concern from a public health standpoint because of the severity of the illnesses and/or because of the higher number of outbreaks and individual cases of foodborne illness associated with these pathogens.

Inhibition of Sprouting and Ripening

A very low radiation dose of 0.15 kGy or less inhibits sprouting of products such as potatoes, yams, onions, garlic, ginger, and chestnuts. It leaves no residues and allows storage at higher temperatures. Irradiation of potatoes, stored at higher temperatures (10o-15oC), has better processing quality 6. Commercial processing of irradiated potatoes has been carried out in Japan since 1973. Irradiation retards the natural decay of fruit and vegetables, thus extending shelf life.

Dis-infestation

The chief problem encountered in preservation of grains and grain products is insect infestation. Irradiation has been shown to be an effective pest control method for these commodities and a good alternative to methyl bromide, the most widely used fumigant for insect control, which is being phased out globally because of its ozone depleting properties. Unlike methyl bromide, irradiation is not an ozone depleting substance and unlike phosphine, the other major fumigant used to control grain pests, irradiation is a fast treatment and its efficacy is not temperature dependent. The dosage required for insect control is reasonably low, in the order of 1 kGy

Extension of shelf-life

The shelf-life of many fruits and vegetables, meat, poultry, fish and seafood can be considerably prolonged by treatment with combinations of low-dose irradiation and refrigeration that do not alter flavour or texture. Many spoilage microorganisms, such as Pseudomonas spp., are relatively sensitive to irradiation. Exposure to a low dose of radiation can slow down the ripening of some fruits, control fungal rot in some others and maturation in certain vegetables, thereby extending their shelf-life.

Current Status of Food Irradiation Technology in India

In India, pilot scale food irradiation facilities existing at Defense laboratory, Jodhpur and Food Technology Division, BARC. For setting up of food irradiation facilities, a license has to be obtainened from the department of Atomic Energy. For any food to be cleared for irradiation a petition has to be filled to the National Monitoring Agency (NMA) set up by the govt. of India for this purpose. An expert group set up by NMA, then studies the proposal and refers it to the Central Committee for Food Standard (CCFS) under the Ministry of Health. After studying the recommendation of the CCFS a person is allowed to set up a food irradiation plant in India. Govt. of India approved the irradiation of onion, potato, and spices for marketing.

Safety of Irradiated Foods

Irradiated food does not become radioactive. In 1981, the Food and Agricultural Organization (FAO) of the United Nations, the International Atomic Energy Agency (IAEA), and the World Health Organization concluded that "any food irradiated up to an average dose of 1 Mrad or less is wholesome for humans as mention in table below and therefore should be approved without further testing" .7

Food Product

Dose

Purpose Of Treatment

Wheat flour

0.2-0.5 kGy

Control of mold

Pork

.3-1.0 kGy

Trichina parasites

Fruit and vegetables

1.0 kGy

Insect control, increase shelf life

Herbs and spices

30 kGy

Sterilization

Poultry

3 kGy

Bacterial pathogen reduction

Meat

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4.5 kGy

Bacterial pathogen reduction

Table: Dosage level of irradiation for diff. food products;

Source: [Radomyski, T. at.el] 8

A joint committee of the FAO, WHO, and IAEA claim that losses of vitamins in foods treated with irradiation doses of 1 kGy or less are minimal and compatible, does not cause a significant decrease in the nutritional quality of foods. [Radomyski, T. at el.] 8

Future Trends and Prospects

Irradiation processing can be used to facilitate storage, movement and distribution of agricultural commodities from production centers to consumption centers and to prevent post harvest losses during these operations. Astronauts and cosmonauts have been taking radiation processed food as part of their ration on the various space flights. Indian Navy has been also taking radiation processed food. With more factual information on radiation processing, public opinion is hoped to change in favor of the technology and play an important role in cutting losses and reducing the dependence on chemical pesticides in collaboration with other existing technologies and solve all the problems of postharvest food losses,

References:

  1. J.F. Diehl, “Food irradiation: is it an alternative to chemical preservatives”, J. Phys., 9, 409-416. (1992).
  2. Satin, M., “Food irradiation, a guidebook”, Economic Publ. Co., Inc. Lancaster, PA., pp.223-236 (1998).
  3. http://www.irradiationequipment.com
  4. R.A. Molins.,” Food Irradiation: Principle and application”. Willey Publ. (First Edition), USA. pp. 213-191(2001).
  5. Fellow P., Food processing technology, principles and practices, 2nd edition. Oxford brooky University, woodhead pub., Washington, DC. (2001)
  6. Thayer, D.W.” Food irradiation: benefits and concerns”. J. Food Quality, 13, 147-169. (1990)
  7. McKinnon, R.G.,” Safety considerations in the design of gamma irradiation facilities and the handling of cobalt-60 sources”. Vol. 3, pp. 563-565. (1988)
  8. Radomyski, T., E. A. Murano, D.G. Olson, and P.S. Murano, “Elimination of pathogens of significance in food by low-dose irradiation: a review. J. Food Protection, 57, 73-86. (1994).