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A Project Note on Use of Irradiation as a Phytosanitary Measure for Cereals and Pulses*

 

India is one of the largest producers of food grains in the world. However, being also one of the most populous countries in the world, its domestic demand often outstrips the supply. The country today is a net importer of food grains, primarily pulses and oilseeds. Import and exports are often faced with quarantine issues related to the presence of quarantine insect pests, pathogens, and noxious weeds in the commodities. Treatment with chemical fumigants such as methyl bromide, phosphine and other fumigants is being currently used to overcome the quarantine barriers. However, the trend is to move away from the fumigants as they pose risk to human health and environment. Radiation processing technology offers an effective alternative to chemicals as phytosanitary or quarantine measure.

 

Radiation Technology

Radiation treatment involves controlled application of energy of ionizing radiation to agricultural commodities, foods and food ingredients. The technology employs either gamma rays emitted by radioisotope such as cobalt-60 or high energy electrons or X-rays generated from machine sources (Table-1). Radiation technology can be harnessed in several ways depending on the need (Table 2). In addition to overcoming quarantine barriers, with adequate storage and packaging regimes, it increases the possibilities of efficient handling and distribution of farm produce, thereby, improving its supply and management. Use of radiation for ensuring biosecurity is likely to become a major issue in future for international trade in agricultural commodities.

 

Low doses of ionizing radiation in the range of 0.25 to 0.1 kGy can be used for disinfestation of stored products, and destroying insect pests of quarantine importance. A technology demonstration unit for this application has been set up by the department of Atomic Energy at Lasalgaon in Nashik District.

 

Wholesomeness and Safety

Preservation of food by radiation offers several advantages listed below. These advantages result from the highly penetrating and effective nature of radiation.

 

  • It is a physical non-additive process
  • It causes minimal changes in food
  • Preserves food in natural form
  • It is a cold process and does not destroy heat-labile aroma constituents
  • It is highly effective
  • Can be applied to pre-packed food
  • Eco-friendly process and does not leave harmful residues
  • The process is safe to workers

 

No other method of food processing has been subjected to such a thorough assessment of safety as the radiation processing. The various aspects of wholesomeness and safety of radiation- processed foods have been studied in great detail. In 1980 a joint FAO/IAEA/WHO Expert Committee on Food Irradiation (JECFI) reviewed the extensive data on wholesomeness collected up to that time and concluded that irradiation of any commodity up to an over all dose of 10 kGy presents no toxicological hazards and introduces no special nutritional or microbiological problems. An Expert Group constituted by WHO in 1992 once again reviewed the wholesomeness data available till then and validated the earlier conclusion of JECFI (WHO, 1994). In 1998 another Expert Group constituted by WHO/FAO/IAEA affirmed the safety of food irradiated to doses above 10 kGy. Codex Alimentarius Commission that sets standards internationally for food and the World Trade Organization have also approved the technique. In addition, a large number of scientific bodies and associations have also endorsed the safety of radiation processed foods. In 1994 Government of India amended Prevention of Food Adulteration Act (1954) Rules and approved irradiation of onion, potato and spices for domestic market. Additional items were approved in April 1998 and in May 2001 (Table 3). A gazette notification has already been issued approving irradiation of food on generic class basis such as fruits and vegetables and cereals and pulses, thus expanding the use of the technology. In 2004, the plant quarantine regulations were amended by the Ministry of Agriculture to include radiation processing as a quarantine measure. This enabled use of the technology for export of mango to USA in 2007 after a gap of 18 years. In India commercial food irradiation is carried out in a facility licensed to do so. The license could be obtained after fulfilling the requirements of the Atomic Energy Regulatory Board (AERB) and the regulatory authority of the importing country. If the facility is to be used as SPS measures for the exportable commodities, it is also required to be accredited by the Directorate of Plant Protection, Quarantine & Storage under the Department of Agriculture & Cooperation of Union Ministry of Agriculture as per IPPC requirement. Government of India has formulated a National Standard for Phytosanitary Measures No. 21 (NSPM-21) describing the infrastructural requirement and procedure of registration.

 

Infrastructure Requirement

 

Land and plant location

The land requirement may vary depending upon the volumes likely to be handled but a minimum of 2-3 acres is required for the irradiator. The land should be away from residential buildings or airport and have no history of calamities like floods and earthquakes. The plant location plays a very decisive role in the economics of radiation processing. It should therefore be decided with utmost care. The plant should have the required feedstock availability throughout the year. This can happen only if the region is endowed with large volumes of storable agricultural commodities during the main farming seasons. Alternatively, the plant should be located near or on the way to warehouses or the port of export and import, so that the material coming from distant places could be processed in transit without incurring additional transport cost. Other important factors for plant location are sufficient availability of electricity, water, labour, and means of communication. The plant should be located near a town with all the modern amenities that would benefit plant employees and prevent flight of trained manpower.

 

Source of radiation

In India, cobalt-60 is supplied by the Board of Radiation and Isotope Technology (BRIT). However, foreign companies like MDS Nordion of Canada and Puridec of UK also supply cobalt-60. The suppliers, when required, undertake the source replenishment and also give guaranty to take back the decayed source in the event of decommissioning of the plant after its useful life. Alternatively, one could use electron beam technology. The electron beam machines could be purchased from the market from a number of suppliers internationally and nationally as per the requirements of product mix and process parameters. As on today, the machine sources are comparatively more expensive and require highly skilled manpower for their maintenance. On the other hand cobalt-60 based plants are simple, more rugged and less expensive to maintain. The requirements of cobalt-60 would vary with the product mix as well as with the nature of application. In general, for low dose irradiation strengths up to 100 kCi are sufficient to have adequate throughput. Similarly, the product mix and throughputs required would determine the machine parameters.

 

Biological shield

Biological shield is the most important component of a radiation processing facility. It is the concrete chamber which houses the source. The radioisotope source is normally stored under water in a pool. In case of a machine source the pool is not required and the machine can be simply switched off. For carrying out radiation processing it is either brought out of the pool or switched on in case of a machine. Biological shield is designed in a way that no radiation can come out of the irradiation chamber when the source is in either exposed or switched on position. A detailed calculation of the shield thickness is carried out by a trained physicist. The shield thickness depends upon the source strength and the likely radiation levels inside the irradiation chamber when the source is fully exposed or switched on. BARC/ BRIT provides the necessary shield calculations and design under the terms of a MoU. A lot of care has to be taken in design and construction of biological shield as any faults in it could lead to problems in getting safety clearance from the regulatory authorities for running the plant.

 

Material handling and conveying

Another major component of the food irradiation plant is the material handling and conveying system. The conveying equipment leads the carriers containing the packages of food to irradiation chamber taking them around the cobalt-60 source or under the electron beam in a machine source allowing delivery of the required dose for achieving a given technological objective. The challenge in the conveyor design lies in getting the desired flexibility for applying different doses in range varying from 0.03-10 kGy for different food commodities for a given source strength and required throughput. Also, the material handling equipment for feeding the conveyor from receipt station and after irradiation unloading and taking to the dispatch station or to cargo hold should be of the matching efficiency. It should also be amenable to manual handling.

 

Laboratory and utilities

A food processing plant must follow good manufacturing practices. It should be operated by trained personnel. The in-coming product should conform to the desired quality and standards. The operator should ensure delivery of the minimum effective dose to achieve the desired technological purpose. Adequate and appropriate post-processing storage is also required for the commodity as per the normal standards. The role of quality control officer is therefore important. An adequately equipped laboratory for dosimetry and testing quality is essential. Besides this adequate power back-up and water storage is also required. The radiation processing plant should conform to the norms of industrial safety. In general radiation processing plants could be designed either in low dose (up to 1 kGy) or high dose (2-10 kGy) category. The requirement of initial source loading would differ in the two by a factor of five and that much savings in terms of capital and replenishment costs. Similarly, the plants for processing meat and seafood would obviously need adequate refrigeration during processing and storage adding to the capital and operational costs.

 

Importance of product mix

The target product mix and the throughputs greatly impact economics of radiation processing plants. One has to have a reasonable idea of the product mix available in the given area and the additional processing costs that it can absorb. Obviously, high value, high throughput and low dose requiring products are more advantageous economically. Depending upon the spare capacity available, the plant can also carry out processing of non-food items like cut-flowers, animal feed, packaging materials and healthcare products. Thus a multi-product irradiator may be more economical than a dedicated single product irradiator.

 

Economics

Economics would depend upon the desired or available product mix for the plant and the dose range required for the treatment of various food and agricultural commodities. A grain irradiator could be a dedicated facility for carrying out disinfestation of cereals, pulses and their products. The dose for this application varies between 0.25 kGy to 1 kGy. Inactivation of nematodes may require higher doses. The source strength required could be 100-300 kCi of cobalt-60. Typical volumes that can be processed annually in this irradiator would be around 70000 tons @10 T/h. The processing cost for insect disinfestation could be around Rs. 180/ ton. A charge of Rs. 500/ ton could allow a payback period of around 3 years (Table 4).

 

 

 

General requirements of the process

 

Good agricultural and manufacturing practices for any food processing technology to become successful the feedstock is of utmost importance. The following two basic principles should be strictly adhered to maintain the in coming product quality. The GAP include the choice of cultivar, agronomic practices, including fertilizer and pest management, harvesting, and post-harvest handling. The GMP relate to the post-harvest handling, and processing before bringing the product for radiation processing. Simple scientific methods can be used to improve GAP and GMP. GAP and GMP can go a long way to increase the effectiveness of any processing technology including irradiation. Good irradiation practices (GIP) are related specifically to the quality control procedures followed in a radiation processing plant. Besides overseeing the quality of incoming products, a radiation processing facility has to ensure delivery of proper dose, labeling of processed product and maintenance of records for inspection at any future date.

 

Table 1. Sources of ionizing radiation used in food processing

 

 

Radiation Sources Energy (MeV)

 

 

Gamma

 

Cobalt-60

 

Cesium-137

 

1.33, 1.17

 

0.66

 

 

Accelerated Electrons

 

Electron Accelerators

 

10 MeV

 

 

X-rays

 

Electrons Accelerators with X-ray converters

 

 

5 MeV

 

Table 2. Applications of Radiation Processing

 

Low dose applications (Less than 1 kGy)

  • Inhibition of sprouting in potato and onion
  • Insect disinfestation in stored grain, pulses and products
  • Destruction of parasites in meat and meat products

 

Medium dose applications (1-10 kGy)

  • Elimination of spoilage microbes in fresh fruits, meat and poultry
  • Elimination of food pathogens in meat and poultry
  • Hygienization of spices and herbs

 

High dose applications (above 10 kGy)

  • Sterilization of food for special requirements
  • Shelf-stable foods without refrigeration

 

Gray is the unit of radiation absorbed dose = 1Joule/kg. The old unit of dose is rad (1Gy = 100 rad)

Table 3. Items of food permitted for irradiation under Indian Prevention of Food Adulteration Act (PFA) Rules

 

Sl.No Name of food Dose of irradiation (kGy)

 

Purpose
Min Max

 

1 Onion 0.03 0.09 Sprout inhibition
2 Potato 0.06 0.15 Sprout inhibition
3 Shallots (small onion) garlic, ginger 0.03 0.15 Sprout inhibition
4 Rice 0.25 1.0 Insect disinfestation
5 Semolina (Sooji or Rawa), Wheat atta and Maida 0.25 1.0 Insect disinfestation
6 Pulses 0.25 1.0 Insect disinfestation
7 Dried sea-food 0.25 1.0 Insect disinfestation
8 Raisins, figs and dried dates 0.25 0.75 Insect disinfestation
9 Mango 0.25 0.75 Shelf-life extension and quarantine treatment
10 Meat and meat products including chicken 2.5 4.0 Shelf-life extension and pathogen control
11 Fresh sea-food 1.0 3.0 Shelf-life extension
2 Frozen sea-food 4.0 6.0 Microbial pathogen control
13 Spices 6.0 14.0 Microbial decontamination

 

 

 

 

Table-4. Economics of a low dose radiation processing unit for cereals, pulses and their products**

Inputs variables Quantities Cost (Rs. Lakh)

Calculated for one year

Cobalt-60 required 100 kCi Cobalt-60 cost/ Ci= Rs. 50
Annual replenishment 12 kCi
Assumed efficiency    0.40
Annual operating hours 7000
Minmum dose   (kGy)    0.25
Throughput/ annum 70000 (~10 ton/h) Ca. theoretical throughput
Number of product handlers 16
Product density 0.5 g/cc
Capital items
Land & development 2.5 acres 50
Irradiation cell & building 250
Cobalt-60 100 kCi 50 Dose required for insect disnfestation is 250 Gy. ***
Conveyer & MHE 10 Ton/h 200
Product & carrier boxes 100 20
Start up cost 25
Total Cost of Input 595
Operating costs
Salary Manager 1 2.40 @ Rs. 20000/month
RSO       1 1.80 @ Rs. 15000/month
QCO       1 1.50 @ Rs. 12000/month
Chemist   1 1.00 @ Rs. 8000/month
Operators 4 3.00 @ Rs. 6000/month
Administrative staff 2 1.20 @ Rs. 5000/month
Handlers   16 8.50 @ Rs. 150/day
Security       6 3.00 @ Rs. 4000/month
Utilities Electricity, water, phone etc 6.00
Cobalt-60 replenishment 12 kCi 6.00
Plant maintenance 5.60
Total Operating Cost   40.00
Cost of Capital (Investment) @ 10% 59.50
Depreciation @ 5% 30.00
Total annual processing cost 129.50 Revenue @ Rs. 500/ ton= Rs. 350 Lakhs, Profit=220.50 Lakhs
Unit processing cost Rs. 180/ ton

~ Rs. 0.20/kg

Payback ~3 years

* Source: BARC/BRIT

**Figures are only indicative

*** Some nematode may require 10 times higher doses

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table-4. Economics of a low dose radiation processing unit for cereals, pulses and their products**

Inputs variables Quantities Cost (Rs. Lakh)

Calculated for one year

Cobalt-60 required 100 kCi Cobalt-60 cost/ Ci= Rs. 50
Annual replenishment 12 kCi
Assumed efficiency    0.40
Annual operating hours 7000
Minmum dose   (kGy)    0.25
Throughput/ annum 70000 (~10 ton/h) Ca. theoretical throughput
Number of product handlers 16
Product density 0.5 g/cc
Capital items
Land & development 2.5 acres 50
Irradiation cell & building 250
Cobalt-60 100 kCi 50 Dose required for insect disnfestation is 250 Gy. ***
Conveyer & MHE 10 Ton/h 200
Product & carrier boxes 100 20
Start up cost 25
Total Cost of Input 595
Operating costs
Salary Manager 1 2.40 @ Rs. 20000/month
RSO       1 1.80 @ Rs. 15000/month
QCO       1 1.50 @ Rs. 12000/month
Chemist   1 1.00 @ Rs. 8000/month
Operators 4 3.00 @ Rs. 6000/month
Administrative staff 2 1.20 @ Rs. 5000/month
Handlers   16 8.50 @ Rs. 150/day
Security       6 3.00 @ Rs. 4000/month
Utilities Electricity, water, phone etc 6.00
Cobalt-60 replenishment 12 kCi 6.00
Plant maintenance 5.60
Total Operating Cost   40.00
Cost of Capital (Investment) @ 10% 59.50
Depreciation @ 5% 30.00
Total annual processing cost 129.50 Revenue @ Rs. 500/ ton= Rs. 350 Lakhs, Profit=220.50 Lakhs
Unit processing cost Rs. 180/ ton

~ Rs. 0.20/kg

Payback ~3 years

* Source: BARC/BRIT

**Figures are only indicative

*** Some nematode may require 10 times higher doses

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