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Commercial implementation of food irradiation
Radiat. Phys. Chem, Vol. 25. Nos. i-3, pp. 215-225, 1985 Printed in Great Britain.
01-k5---5724/85 $3.00 + .00 Pergamon Press Ltd
COMMERCIAL IMPLLMENTATION OF FOOD IRRADIATION
M. A. Welt
Radiation Technology, Inc., Lake Denmark Road, Rockaway, N.J. 07866, USA
ABSTRACT In July 1981, the first specifically designed multi-purpose irradiation facility for food irradiation was put into service by the Radiation Technology, Inc. subsidiary Process Technology, Inc. in West Memphis, Arkansas. The operational experience gained, resulted in an enhanced design which was put into commercial service in Haw River, North Carolina, by another subsidiary, Process Technology (N.C.), Inc. in October 1983. These facilities have enabled the food industry to assess the commercial viability of food irradiation. Further impetus towards commercialization of food irradiation was gained in March 1981 with the filing in the Federal Register, by the FDA, of an Advanced Proposed Notice of Rulemaking for Food Irradiation. Two years later in July 1983, the FDA approved the first food additive regulation involving food irradiation in nineteen years, when they approved the Radiation Technology, Inc. petition calling for the sanitization of spices, onion powder and garlic powder at a maximum dosage of i0 kGy. Since obtaining the spice irradiation approval, the FDA has accepted four additional petitions for filing in the Federal Register. One of the petitions which extended spice irradiation to include insect disinfestation has issued into a regulation while the remaining petitions covering the sanitization of herbs, spice blends, vegetable seasonings and dry powdery enzymes as well as the petition to irradiate hog carcasses and pork products for trichinae control at I kGy, are expected to issue either before the end of 1984 or early in 1985. More recently, food irradiation advocates in the United States received another vote of confidence by the announcement that a joint venture food irradiation facility to be constructed in Hawaii by Radiation Technology, is backed by a contractual committment for the processing of 40 million pounds of produce per year. Another step was taken when the Port of Salem, New Jersey announced that the Radiation Technology Model RT-4104-4048(TM) irradiation facility was chosen to interface with the only East Coast grain elevator in the United States. These factors, along with concern over the ban of EDB as a post harvest fumigant, coupled with the expected FDA action to approve the use of irradiation for the insect disinfestation of fruit and vegetables, should finally permit the commercial implementation of food irradiation to take hold in the United States. KEYWORDS Food irradiation, Cobalt-60, Cesium 137, Model RT-4104-4048 (TM) Multi-purpose Irradlator, pallet irradiator. INTRODUCTION There is now a commercial endeavor gaining strength around the world based on the use of ionizing energy for the preservation of food. Although there have been high hopes for the commercialization over the past three decades, it was not until the last few years that sufficient breakthroughs involving regulatory approvals were coupled with the required radiation technology to permit economically viable food irradiation. The regulatory realism may well have been influenced by a growing public concern over pesticide residues in our food and the use of chemical food additives. A recent Department of Energy study (i), involving consumer reaction to irradiated food verified this conclusion. These factors are helping to break down the barriers of prejudice against the radiation preservation of food, Another factor beginning to emerge is the renewed interest on the part of the food industry with radiation preservation or benefaction of various food items. It stands to reason that commercial implementation of food irradiation is impossible without the full cooperation and 215
210
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support of the food industry. During the 1950's and 1960's, meat companies in particular, as well as pet food manufacturers, supported extensive research and developmen~ work in the area of food irradiation. In fact, plans were well underway to build a semi-commercial meat and pe= food irradiation facility (2), with Department of Defense procurement support, when the FDA discouraged such an action by rejecting a petition to permit the irradiation sterilization of ham and by withdrawing the regulation previously granted permitting the sale of radiation sterilized bacon in the United States. The lack of a commercial irradiation facility for demonstrating the feasibility of the process for the treatment of food, remained a serious drawback, until 1981 when Radiation Technology, Inc. put into service a multipurpose, computer controlled pallet irradiator (3), operated by its subsidiary, Process Technology Inc. in West Memphis, Arkansas. Two years later, in 1983, an enhanced version of the West Memphis facility, the Model RT-4104-4048(TM) was put into service by another subsidiary, Process Technology (N.C.), Inc. in Haw River, North Carolina. Based on actual production experience involving commercial shipments of citrus products, spices, seafood, poultry, bagged grains, onion powder, garlic powder, etc., Radiation Technology has been able to demonstrate to the domestic as well as foreign food industries that the question of whethe~ or not the technology exists to irradiate food at any dose level or for any purpose, is no longer a valid concern. The Model RT-4101-4048(TM) has been chosen for the Port of Salem, New Jersey, where it will interface with the only grain elevator on the East Coast in the United States. Another unit is to be located in Hawaii for the processing of papaya and other tropical fruit, at a contracted level of no less than 40 million pounds per year. A further indication of the acceptance of the technology was the licensing of the Model RT-4104-4048(TM) to Simon Food Engineering Ltd. of Stockport, U.K., Toyo Engineering Corp. of Tokyo, Japan, and to Giant Python Holdings, Ltd. of Hamilton, Bermuda. REGULATORY
CONSIDERATIONS
Since 1980 there have been a number of important regulatory achievements in the United States which have removed much of the lingering doubt concerning the ultimate adoption and commercial implementation of food irradiation. One can now reasonably speculate that the day when unrestricted use of this technology becomes commonplace, cannot be too far off. The initial breakthrough was acceptance by the Food and Drug Administration (FDA) on April 2S, 1980, of a food additive petition filed by Radiation Technology, Inc., which called for the radiation sanitization of spices at a dose not to exceed i0 kGy (4). This was the first food irradiation petition accepted by the FDA since the approval of potato irradiation for sprout inhibition and for the insect disinfestation of wheat and wheat flour in 1964 (5,6). The next regulatory item of significance was the July 1980 publication by the Bureau of Food Irradiated Food Committee (BFIFC), a report titled, "Recommendations for Evaluating the Safer! of Irradiated Foods". This report was of special significance since it represented the firsl instance where the FDA was willing to provide insight into their thinking concerning food safety questions associated with food irradiation. Further, the high esteem with which nations of the world regard the FDA's judgement, did much to encourage irradiated food export~ from the United States. The BFIFC report provided the following conclusions: i. Any food irradiated at doses not exceeding I kGy is safe and wholesome for human consumption without the need for additional toxicological or animal feeding studies. This conclusion was based on established radiation chemistry data which permitted the committee to estimate that no more than i ppm of "unique radiolytic productS" (LAP's) would be formed by irradiating food at room temperature to that dose. 2. Irradiated food would be considered safe without the need for additional animal feeding studies if the total G value for all radiolytic products was less than one. 3. Dry foods, such as spices or condiments, which constitute less than 0.01~ of a daily diet, can be irradiated up to a dose of 50 kGy without any further toxicological or animal feeding experimentation. Since the above criteria resulted from calculations based on room temperature irradiation, it must be emphasized that 1 kGy, was an arbitrary result, whereas the choice of i ppm of URP's, and a total G value of I, were based on the FDA's judgement which constituted "good science", in the proposed food irradiation regulation. Obviously, these conditions could be met by irradiating the product at sub-zero temperatures, as is the case with the production of shelf-stable radiation sterilized diets. By freezing the water in food, migration of the hydoxyl radical is restricted, reducing the chemical changes that take place. On March 31, 1981 the FDA filed in the Federal Register an Advanced Proposed Ru!emaking for Food Irradiation, based on the BFIFC report. While public comments were still being reviewed prior to issuance of a Notice of Rulemaking, the FDA issued a regulation on July 5, 1983, based on the Radiation Technology spice petition. This was the first food irradiation approval in the United States in 19 years. These several factors, followed on July 8, 1983, by the adoption of an international standard for food irradiation by the Codex Alimentarius Commission, which provided for the irradiation of any food to an overall average dose of i0 kGy, without concern for reducing wholesomeness or for incuring any toxicological problems. Technical credibility was now being
Commercial Implementation of Food Irradiation
217
established, and the food industry began to show more than simple curiosity with regard to potential commercial applications. In fact, two of the petitions filed by Radiation Technology were financed by food companies who obviously believed that food irradiation would be beneficial to their products and business. However, the complexity and diversity of the food production and processing industry, left lingering doubts as to whether radiation processing could become economically viable on a commercial scale. For example, a factor of 2000 spans the dose requirements from 0.025 kGy for shelf life extension of avacado to 50.0 kGy for shelf-stable sterile diets. Further, most food, espcially fruit and vegetables are seasonal, with variations in harvest yield, and with widely distributed production. It was not feasible to utilize a medical product sterilization irradiator for meeting the needs of the food industry, since the conveyor systems were not designed for bulky and heavy products, and it was not practical to attain the dose variations required by simply speeding up or slowing down a conveyor system. This situation persisted until July 1981 when the first specifically designed multi-purpose food irradlator was put into service in West Memphis, Arkansas by Process Technology, Inc. TECHNICAL CONSIDERATIONS The operational experience gained in West Memphis, led to the enhanced Model RT-4101-4048(TM), which permitted the irradiation of standard 40"x48" pallets, containing up to 2500 pounds of product per pallet. The facility was a radical departure from any previously built irradiator, since it permitted individual pallets to be processed independent of each other, and did not require each pallet to take the same route through the system. Details of the system have been published elsewhere (7,8,9), with additional performance characteristics discussed in this section. Figure 1 shows a typical plant layout, with the irradiator maze containing an entrance and exit labyrinth. This design feature permits the segregation of unprocessed and processed products in the warehouse. Figure 2 provides a cross-sectional view of the irradiator and Fig. 3 is a schematic of the irradiator, showing the four passes (two on either side of the single source), and the transfer mechanisms which translate the pallets from one side of the source to the other. Figure 4 is a schematic side view, showing the product height in relation to the source height. The source plaque contains 16 modules, with each module capable of holding approximately 32 source pencils, approximately 18 inches long. The source plaque is approximately 84 inches high by 72 inches wide, and is designed to permit exchange of the lower modules without removing the upper modules, or to operate with only the middle eight modules, if higher dose rates are required when a relatively low Cobalt-60 source loading is in place. Figure 5 shows the actual dose distribution through two centrally positioned pallets (Routine 6), for a given product bulk density. It is evident from the dose curve that a very low maximum to minimum dose distribution is possible when operations are restricted to the outer passes. Figure 6 details the nine operating routines which are controlled by the computer control system. Since the system is designed for both batch and automatic operation, there are actually 18 different irradiation procedures available, which can control the dose ratio, processing dose rate, or simply the optimum cycle for a given product volume. Since regulatory constraints or product response may limit the maximum dose that can be tolerated, the usual procedure is to reduce the height of the target with respect to the source as shown in Fig. 7. The consequence of reducing the product height is to lessen the product throughput and hence increase the unit processing cost. The Model RT-4101-4048(TM) permits loads to be shifted as shown in Fig. 8, so that higher dose rates can be achieved, resulting in higher unit output. Another alternative is shown in Fig. 9, in which the virtues of a two level quadrent source irradiator are simulated by the one level RT-4104. In this case the target is split onto two pallets of equal height, and stacked on one another. After completing a given processing routine the pallets are reversed from top to bottom, and the processing routine previously used is repeated. Since the original position of high dose is switched to the position of low dose, the max-min dose ratio is greatly reduced as shown by comparing Figs. 7 and 9. Although the run time is increased in the latter case, the unit processing cost is reduced, due to the higher throughput. An important feature of the RT-4101 is the computer control system, which permits the irradiation of more than one product at a given time, by making use of the sophisticated conveyor system, which enables individual pallets to be placed at different positions within the irradiator so that they do not interfere with the dose delivered to each other. In some cases, the system can actually process a high dose requirement product, i.e. radiation sterilized food, utilizing Routine 2, while a low dose requirement such as insect disinfestatlon is handled with Routine 8, as shown in Fig. I0. Throughput data is shown in Fig. ii for the product density and processing routine given. The "Load-Shlfter"(TM)* is also compared in order to appreciate the impact on throughput. Figure 12 shows throughput data for the case described in Fig. I0, in which two loads are being processed simultaneously, with a computer printout certification issued for each product. The operator of the RT-4101 is able to check the status of the irradiator at any moment by utilizing the video graphics which are available as part of the interfacing computer program. Figure 13 shows the video graphic "Menu", Fig. 14 shows a typical "Status Display", and Fig. 15 shows the video representation of the Irradiator during operation in Routine 2. The
215
~|. ~'ELT
computer certification print-out is automatically compared with an experimental protocol for the given product, in order to perform ongoing audits which insure accurate processing performance from run to run. NEAR TERM POTENTIAL In order to determine how many irradiation facilities of the Model RT-4101-4048(TM) type would be required to process high volume commodities in the United States, we have considered the 1983 production estimates for shrimp, pork, and chicken, with the assumption that only 10% of the total is to be irradiated. The shrimp and chicken were to be radurized and/or radicidized at a minimum dose of 3 and 1.25 kGy respectively, and the pork treated for trichinae elimination at 0.25 kGy. The results are tabulated in Fig. 16. Assuming 25% efficiency, 8000 hour per year operating cycle, and a i megacurie Cobalt-60 loading per plant, a total of 12 megacuries would be required for the three commodities chosen. The Model RT4101 has been designed to handle Cesium-137 sources as well as Cobalt-60, and based on the U.S. DOE committment to make Cesium-137 available there should be no shortage of radiation sources assuming that Cobalt-60 production in Canada is increased to the 120 megacuries per year figure that has been announced, starting in about 18 months. The Model RT-4101 is capable of turning out one pallet containing 2500 pounds of product per minute, a production rate demonstrated by the irradiation of 1800 pounds of pallatized citrus products per minute at the Process Technology (N.C.), Inc. facility in Haw River, North Carolina. Production of irradiated spices, onion powder, and garlic powder for the U.S. market will probably exceed i0 million pounds for 1984, and should exceed i00 million pounds in 1985 with passage of the FDA's regulation for food irradiation which increases the maximum dose to 30 kGy and which will clarify the labelling question. The contribution of herbs, spice blends, vegetable seasonings and food grade enzymes could provide another 50 million pounds of processing during 1985. The potential for exporting irradiated foods from the U.S. continues to expand, The decisiol by the Environmental Protection Agency to ban the use of EDB as a post harvest fumigant will certainly lead to an expansion of food irradiation both for domestic consumption as well as for export to nations receiving U.S. produce such as citrus products. Over the past decade, considerable quantities of irradiated frozen shrimp and frog's legs have been exported to nations accepting these processed products. With the establishment of an international standard for food irradiation, endorsed by the World Health Organization, the Food and Agricultural Organization and the International Atomic Energy Agency, opportunities for food irradiation appear brighter than ever. U.S. food producers are now looking at foreign markets for fresh product with an enhanced shelf life due to irradiation, and most significantly, interest is peaking in the export of shelf-stable food that does not require freezing or refrigeration for shipping or storage. Radiation Technology, Inc. is now routinely producing and warehousing a wide variety of shelf-stable meat, poultry, fish and seafood products, similar to the rations supplied to the space shuttle astronauts, and plans to add shelf-stable fruit and vegetable products to round out the balanced diet. CONCLUSIONS Recent positive developments in regulatory matters involving food irradiation appear to be opening the door to commercial implementation of the technology. Experience gained over five years in operating multi-purpose food irradiation facilities in the United States have demonstrated the technical and economic feasibility of the radiation preservation of food for a wide variety of purposes. Public educaSion regarding food irradiation have been intensified, especially wish the growing favorable involvement of food trade associations, the USDA, and the American Medical Association. After 41 years of development effort, food irradiation will become a commercial reality in 1985. *Patent pending REFERENCES (i) Anon., "Consumer Reaction to Irradiated Food", Wiese Research Associates, Omaha, NE, (DOE and National Pork Producers Council, 1983) (2) Goldblith, S.A., "Historical Development of Food Irradiation", FOOD IRRADIATION, Proe=edings of a Symposium, Karlsruhe, 6-10 June 1966 organized by the IAEA/and FAO. (3) Welt, M. A., "New Facility Announcement by: Radiation Technology, Inc.", Press Release issued June 9, 1981. (4) Federal Register 45(203):69045, 10/17/80. (5, 6) Code of Federal Regulations, Title 21, Section 179.22 (7) Welt, M. A., "A Unique and Versatile Gamma Irradiator for Radiation Preservation of Food", J. Food Safety 5:4, 1983 (8) Welt, M. A., "A Commercial Multi-purpose Radiation Processing Facility for Hawaii", presented at the International Conference on Radiation Disinfestation of Food and Agriculture Products, Honolulu, Hawaii, 1983. (9) Welt, M. A., "Economics and Operations of Food Irradiation", presented at National Symposium on Food Irradiation, Palmerston North, New Zealand.
Commercial Implementation of Food Irradiation
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Commercial Implementation of Food Irradiation
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Commercial [mplementation of Food Irradiation
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Commercial Implementation of Food Irradiation
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01-k5---5724/85 $3.00 + .00 Pergamon Press Ltd
COMMERCIAL IMPLLMENTATION OF FOOD IRRADIATION
M. A. Welt
Radiation Technology, Inc., Lake Denmark Road, Rockaway, N.J. 07866, USA
ABSTRACT In July 1981, the first specifically designed multi-purpose irradiation facility for food irradiation was put into service by the Radiation Technology, Inc. subsidiary Process Technology, Inc. in West Memphis, Arkansas. The operational experience gained, resulted in an enhanced design which was put into commercial service in Haw River, North Carolina, by another subsidiary, Process Technology (N.C.), Inc. in October 1983. These facilities have enabled the food industry to assess the commercial viability of food irradiation. Further impetus towards commercialization of food irradiation was gained in March 1981 with the filing in the Federal Register, by the FDA, of an Advanced Proposed Notice of Rulemaking for Food Irradiation. Two years later in July 1983, the FDA approved the first food additive regulation involving food irradiation in nineteen years, when they approved the Radiation Technology, Inc. petition calling for the sanitization of spices, onion powder and garlic powder at a maximum dosage of i0 kGy. Since obtaining the spice irradiation approval, the FDA has accepted four additional petitions for filing in the Federal Register. One of the petitions which extended spice irradiation to include insect disinfestation has issued into a regulation while the remaining petitions covering the sanitization of herbs, spice blends, vegetable seasonings and dry powdery enzymes as well as the petition to irradiate hog carcasses and pork products for trichinae control at I kGy, are expected to issue either before the end of 1984 or early in 1985. More recently, food irradiation advocates in the United States received another vote of confidence by the announcement that a joint venture food irradiation facility to be constructed in Hawaii by Radiation Technology, is backed by a contractual committment for the processing of 40 million pounds of produce per year. Another step was taken when the Port of Salem, New Jersey announced that the Radiation Technology Model RT-4104-4048(TM) irradiation facility was chosen to interface with the only East Coast grain elevator in the United States. These factors, along with concern over the ban of EDB as a post harvest fumigant, coupled with the expected FDA action to approve the use of irradiation for the insect disinfestation of fruit and vegetables, should finally permit the commercial implementation of food irradiation to take hold in the United States. KEYWORDS Food irradiation, Cobalt-60, Cesium 137, Model RT-4104-4048 (TM) Multi-purpose Irradlator, pallet irradiator. INTRODUCTION There is now a commercial endeavor gaining strength around the world based on the use of ionizing energy for the preservation of food. Although there have been high hopes for the commercialization over the past three decades, it was not until the last few years that sufficient breakthroughs involving regulatory approvals were coupled with the required radiation technology to permit economically viable food irradiation. The regulatory realism may well have been influenced by a growing public concern over pesticide residues in our food and the use of chemical food additives. A recent Department of Energy study (i), involving consumer reaction to irradiated food verified this conclusion. These factors are helping to break down the barriers of prejudice against the radiation preservation of food, Another factor beginning to emerge is the renewed interest on the part of the food industry with radiation preservation or benefaction of various food items. It stands to reason that commercial implementation of food irradiation is impossible without the full cooperation and 215
210
N1. %~,EL r
support of the food industry. During the 1950's and 1960's, meat companies in particular, as well as pet food manufacturers, supported extensive research and developmen~ work in the area of food irradiation. In fact, plans were well underway to build a semi-commercial meat and pe= food irradiation facility (2), with Department of Defense procurement support, when the FDA discouraged such an action by rejecting a petition to permit the irradiation sterilization of ham and by withdrawing the regulation previously granted permitting the sale of radiation sterilized bacon in the United States. The lack of a commercial irradiation facility for demonstrating the feasibility of the process for the treatment of food, remained a serious drawback, until 1981 when Radiation Technology, Inc. put into service a multipurpose, computer controlled pallet irradiator (3), operated by its subsidiary, Process Technology Inc. in West Memphis, Arkansas. Two years later, in 1983, an enhanced version of the West Memphis facility, the Model RT-4104-4048(TM) was put into service by another subsidiary, Process Technology (N.C.), Inc. in Haw River, North Carolina. Based on actual production experience involving commercial shipments of citrus products, spices, seafood, poultry, bagged grains, onion powder, garlic powder, etc., Radiation Technology has been able to demonstrate to the domestic as well as foreign food industries that the question of whethe~ or not the technology exists to irradiate food at any dose level or for any purpose, is no longer a valid concern. The Model RT-4101-4048(TM) has been chosen for the Port of Salem, New Jersey, where it will interface with the only grain elevator on the East Coast in the United States. Another unit is to be located in Hawaii for the processing of papaya and other tropical fruit, at a contracted level of no less than 40 million pounds per year. A further indication of the acceptance of the technology was the licensing of the Model RT-4104-4048(TM) to Simon Food Engineering Ltd. of Stockport, U.K., Toyo Engineering Corp. of Tokyo, Japan, and to Giant Python Holdings, Ltd. of Hamilton, Bermuda. REGULATORY
CONSIDERATIONS
Since 1980 there have been a number of important regulatory achievements in the United States which have removed much of the lingering doubt concerning the ultimate adoption and commercial implementation of food irradiation. One can now reasonably speculate that the day when unrestricted use of this technology becomes commonplace, cannot be too far off. The initial breakthrough was acceptance by the Food and Drug Administration (FDA) on April 2S, 1980, of a food additive petition filed by Radiation Technology, Inc., which called for the radiation sanitization of spices at a dose not to exceed i0 kGy (4). This was the first food irradiation petition accepted by the FDA since the approval of potato irradiation for sprout inhibition and for the insect disinfestation of wheat and wheat flour in 1964 (5,6). The next regulatory item of significance was the July 1980 publication by the Bureau of Food Irradiated Food Committee (BFIFC), a report titled, "Recommendations for Evaluating the Safer! of Irradiated Foods". This report was of special significance since it represented the firsl instance where the FDA was willing to provide insight into their thinking concerning food safety questions associated with food irradiation. Further, the high esteem with which nations of the world regard the FDA's judgement, did much to encourage irradiated food export~ from the United States. The BFIFC report provided the following conclusions: i. Any food irradiated at doses not exceeding I kGy is safe and wholesome for human consumption without the need for additional toxicological or animal feeding studies. This conclusion was based on established radiation chemistry data which permitted the committee to estimate that no more than i ppm of "unique radiolytic productS" (LAP's) would be formed by irradiating food at room temperature to that dose. 2. Irradiated food would be considered safe without the need for additional animal feeding studies if the total G value for all radiolytic products was less than one. 3. Dry foods, such as spices or condiments, which constitute less than 0.01~ of a daily diet, can be irradiated up to a dose of 50 kGy without any further toxicological or animal feeding experimentation. Since the above criteria resulted from calculations based on room temperature irradiation, it must be emphasized that 1 kGy, was an arbitrary result, whereas the choice of i ppm of URP's, and a total G value of I, were based on the FDA's judgement which constituted "good science", in the proposed food irradiation regulation. Obviously, these conditions could be met by irradiating the product at sub-zero temperatures, as is the case with the production of shelf-stable radiation sterilized diets. By freezing the water in food, migration of the hydoxyl radical is restricted, reducing the chemical changes that take place. On March 31, 1981 the FDA filed in the Federal Register an Advanced Proposed Ru!emaking for Food Irradiation, based on the BFIFC report. While public comments were still being reviewed prior to issuance of a Notice of Rulemaking, the FDA issued a regulation on July 5, 1983, based on the Radiation Technology spice petition. This was the first food irradiation approval in the United States in 19 years. These several factors, followed on July 8, 1983, by the adoption of an international standard for food irradiation by the Codex Alimentarius Commission, which provided for the irradiation of any food to an overall average dose of i0 kGy, without concern for reducing wholesomeness or for incuring any toxicological problems. Technical credibility was now being
Commercial Implementation of Food Irradiation
217
established, and the food industry began to show more than simple curiosity with regard to potential commercial applications. In fact, two of the petitions filed by Radiation Technology were financed by food companies who obviously believed that food irradiation would be beneficial to their products and business. However, the complexity and diversity of the food production and processing industry, left lingering doubts as to whether radiation processing could become economically viable on a commercial scale. For example, a factor of 2000 spans the dose requirements from 0.025 kGy for shelf life extension of avacado to 50.0 kGy for shelf-stable sterile diets. Further, most food, espcially fruit and vegetables are seasonal, with variations in harvest yield, and with widely distributed production. It was not feasible to utilize a medical product sterilization irradiator for meeting the needs of the food industry, since the conveyor systems were not designed for bulky and heavy products, and it was not practical to attain the dose variations required by simply speeding up or slowing down a conveyor system. This situation persisted until July 1981 when the first specifically designed multi-purpose food irradlator was put into service in West Memphis, Arkansas by Process Technology, Inc. TECHNICAL CONSIDERATIONS The operational experience gained in West Memphis, led to the enhanced Model RT-4101-4048(TM), which permitted the irradiation of standard 40"x48" pallets, containing up to 2500 pounds of product per pallet. The facility was a radical departure from any previously built irradiator, since it permitted individual pallets to be processed independent of each other, and did not require each pallet to take the same route through the system. Details of the system have been published elsewhere (7,8,9), with additional performance characteristics discussed in this section. Figure 1 shows a typical plant layout, with the irradiator maze containing an entrance and exit labyrinth. This design feature permits the segregation of unprocessed and processed products in the warehouse. Figure 2 provides a cross-sectional view of the irradiator and Fig. 3 is a schematic of the irradiator, showing the four passes (two on either side of the single source), and the transfer mechanisms which translate the pallets from one side of the source to the other. Figure 4 is a schematic side view, showing the product height in relation to the source height. The source plaque contains 16 modules, with each module capable of holding approximately 32 source pencils, approximately 18 inches long. The source plaque is approximately 84 inches high by 72 inches wide, and is designed to permit exchange of the lower modules without removing the upper modules, or to operate with only the middle eight modules, if higher dose rates are required when a relatively low Cobalt-60 source loading is in place. Figure 5 shows the actual dose distribution through two centrally positioned pallets (Routine 6), for a given product bulk density. It is evident from the dose curve that a very low maximum to minimum dose distribution is possible when operations are restricted to the outer passes. Figure 6 details the nine operating routines which are controlled by the computer control system. Since the system is designed for both batch and automatic operation, there are actually 18 different irradiation procedures available, which can control the dose ratio, processing dose rate, or simply the optimum cycle for a given product volume. Since regulatory constraints or product response may limit the maximum dose that can be tolerated, the usual procedure is to reduce the height of the target with respect to the source as shown in Fig. 7. The consequence of reducing the product height is to lessen the product throughput and hence increase the unit processing cost. The Model RT-4101-4048(TM) permits loads to be shifted as shown in Fig. 8, so that higher dose rates can be achieved, resulting in higher unit output. Another alternative is shown in Fig. 9, in which the virtues of a two level quadrent source irradiator are simulated by the one level RT-4104. In this case the target is split onto two pallets of equal height, and stacked on one another. After completing a given processing routine the pallets are reversed from top to bottom, and the processing routine previously used is repeated. Since the original position of high dose is switched to the position of low dose, the max-min dose ratio is greatly reduced as shown by comparing Figs. 7 and 9. Although the run time is increased in the latter case, the unit processing cost is reduced, due to the higher throughput. An important feature of the RT-4101 is the computer control system, which permits the irradiation of more than one product at a given time, by making use of the sophisticated conveyor system, which enables individual pallets to be placed at different positions within the irradiator so that they do not interfere with the dose delivered to each other. In some cases, the system can actually process a high dose requirement product, i.e. radiation sterilized food, utilizing Routine 2, while a low dose requirement such as insect disinfestatlon is handled with Routine 8, as shown in Fig. I0. Throughput data is shown in Fig. ii for the product density and processing routine given. The "Load-Shlfter"(TM)* is also compared in order to appreciate the impact on throughput. Figure 12 shows throughput data for the case described in Fig. I0, in which two loads are being processed simultaneously, with a computer printout certification issued for each product. The operator of the RT-4101 is able to check the status of the irradiator at any moment by utilizing the video graphics which are available as part of the interfacing computer program. Figure 13 shows the video graphic "Menu", Fig. 14 shows a typical "Status Display", and Fig. 15 shows the video representation of the Irradiator during operation in Routine 2. The
215
~|. ~'ELT
computer certification print-out is automatically compared with an experimental protocol for the given product, in order to perform ongoing audits which insure accurate processing performance from run to run. NEAR TERM POTENTIAL In order to determine how many irradiation facilities of the Model RT-4101-4048(TM) type would be required to process high volume commodities in the United States, we have considered the 1983 production estimates for shrimp, pork, and chicken, with the assumption that only 10% of the total is to be irradiated. The shrimp and chicken were to be radurized and/or radicidized at a minimum dose of 3 and 1.25 kGy respectively, and the pork treated for trichinae elimination at 0.25 kGy. The results are tabulated in Fig. 16. Assuming 25% efficiency, 8000 hour per year operating cycle, and a i megacurie Cobalt-60 loading per plant, a total of 12 megacuries would be required for the three commodities chosen. The Model RT4101 has been designed to handle Cesium-137 sources as well as Cobalt-60, and based on the U.S. DOE committment to make Cesium-137 available there should be no shortage of radiation sources assuming that Cobalt-60 production in Canada is increased to the 120 megacuries per year figure that has been announced, starting in about 18 months. The Model RT-4101 is capable of turning out one pallet containing 2500 pounds of product per minute, a production rate demonstrated by the irradiation of 1800 pounds of pallatized citrus products per minute at the Process Technology (N.C.), Inc. facility in Haw River, North Carolina. Production of irradiated spices, onion powder, and garlic powder for the U.S. market will probably exceed i0 million pounds for 1984, and should exceed i00 million pounds in 1985 with passage of the FDA's regulation for food irradiation which increases the maximum dose to 30 kGy and which will clarify the labelling question. The contribution of herbs, spice blends, vegetable seasonings and food grade enzymes could provide another 50 million pounds of processing during 1985. The potential for exporting irradiated foods from the U.S. continues to expand, The decisiol by the Environmental Protection Agency to ban the use of EDB as a post harvest fumigant will certainly lead to an expansion of food irradiation both for domestic consumption as well as for export to nations receiving U.S. produce such as citrus products. Over the past decade, considerable quantities of irradiated frozen shrimp and frog's legs have been exported to nations accepting these processed products. With the establishment of an international standard for food irradiation, endorsed by the World Health Organization, the Food and Agricultural Organization and the International Atomic Energy Agency, opportunities for food irradiation appear brighter than ever. U.S. food producers are now looking at foreign markets for fresh product with an enhanced shelf life due to irradiation, and most significantly, interest is peaking in the export of shelf-stable food that does not require freezing or refrigeration for shipping or storage. Radiation Technology, Inc. is now routinely producing and warehousing a wide variety of shelf-stable meat, poultry, fish and seafood products, similar to the rations supplied to the space shuttle astronauts, and plans to add shelf-stable fruit and vegetable products to round out the balanced diet. CONCLUSIONS Recent positive developments in regulatory matters involving food irradiation appear to be opening the door to commercial implementation of the technology. Experience gained over five years in operating multi-purpose food irradiation facilities in the United States have demonstrated the technical and economic feasibility of the radiation preservation of food for a wide variety of purposes. Public educaSion regarding food irradiation have been intensified, especially wish the growing favorable involvement of food trade associations, the USDA, and the American Medical Association. After 41 years of development effort, food irradiation will become a commercial reality in 1985. *Patent pending REFERENCES (i) Anon., "Consumer Reaction to Irradiated Food", Wiese Research Associates, Omaha, NE, (DOE and National Pork Producers Council, 1983) (2) Goldblith, S.A., "Historical Development of Food Irradiation", FOOD IRRADIATION, Proe=edings of a Symposium, Karlsruhe, 6-10 June 1966 organized by the IAEA/and FAO. (3) Welt, M. A., "New Facility Announcement by: Radiation Technology, Inc.", Press Release issued June 9, 1981. (4) Federal Register 45(203):69045, 10/17/80. (5, 6) Code of Federal Regulations, Title 21, Section 179.22 (7) Welt, M. A., "A Unique and Versatile Gamma Irradiator for Radiation Preservation of Food", J. Food Safety 5:4, 1983 (8) Welt, M. A., "A Commercial Multi-purpose Radiation Processing Facility for Hawaii", presented at the International Conference on Radiation Disinfestation of Food and Agriculture Products, Honolulu, Hawaii, 1983. (9) Welt, M. A., "Economics and Operations of Food Irradiation", presented at National Symposium on Food Irradiation, Palmerston North, New Zealand.
Commercial Implementation of Food Irradiation
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219
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Commercial Implementation of Food Irradiation
221
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Commercial [mplementation of Food Irradiation
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223
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Commercial Implementation of Food Irradiation
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THEORETICAL REQUIREMENTSFOR HEAT PROCESSING PRODUCT PRODUCTION (,ms) 1983
PRODUCT(ON(,,,s) DOSE(~) PROCESSING REQUIRERENTS"2 lOZ
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Fig.
16
Results of Shrimp,
Pork, and Chicken