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United States Department of Agriculture
Washington, D.C. 20250-3700

Irradiation of Meat and Poultry Products

Ionizing Radiation as an Additive in Unrefrigerated Meat Food Products

U.S. Department of Agriculture
Food Safety and Inspection Service

Volume 1 of 1

PETITIONER: United States Department of Agriculture
Food Safety and Inspection Service
ADDRESS: Washington, DC 20250
DATE: August 19, 1999
ADDITIVE: Ionizing radiation
PURPOSE OF
ADDITIVE:
Treatment of unrefrigerated, uncooked meat, meat byproducts, and certain meat food products to reduce levels of foodborne pathogens and extend shelf-life

Petitions Control Branch
Food and Drug Administration
Department of Health and Human Services
Washington, DC 20204

Dear Sirs:

The undersigned, Food Safety and Inspection Service (FSIS), submits this petition, pursuant to 409(b)(1) of the Federal Food, Drug, and Cosmetic Act, with respect to the use of ionizing radiation as an additive in unrefrigerated, uncooked meat, meat byproducts, and certain other meat food products to reduce levels of food borne pathogens and to extend product shelf-life.

The petition, enclosed in triplicate, consists of the following sections, in accordance with 21 CFR 171.1:

        (A) the name and all pertinent information concerning the food additive;

        (B) a statement of the conditions of the proposed use of such additive, including all directions, recommendations, and suggestions proposed for the use of such additive, and including specimens of its proposed labeling;

        (C) all relevant data bearing on the physical or other technical effect such additive is intended to produce, and the quantity of such additive required to produce such effect;

        (D) a description of practicable methods for determining the quantity of such additive in or on food, and any substance formed in or on food, because of its use; and

        (E) full reports of investigations made with respect to the safety for use of such additive, including full information as to the methods and controls used in conducting such investigations.

Finally, FSIS requests that this petition receive expedited review, as is described in the Food and Drug Administration’s guidance dated January 4, 1999. The use of sources of ionizing radiation as an additive in unrefrigerated, uncooked meat food products may significantly decrease the incidence of food borne illness through its antimicrobial effect against human pathogens, including Escherichia coli O157:H7.

Sincerely,

 

Thomas J. Billy
Administrator

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(A) Identification of Food Additive

Sources of ionizing radiation approved in 21 CFR 179.26(a), namely, cobalt-60 or cesium-37 sources, electron beam accelerators, or x-ray generators, will be used to treat unrefrigerated, uncooked meat, meat byproducts, and certain meat food products (hereafter referred to as "meat food products" when discussed as a group).

(B) Proposed Use

Ionizing radiation can significantly reduce the levels of many microbial pathogens commonly found in uncooked meat food products, including Salmonella spp. and Escherichia coli O157:H7. Further, through the reduction of nonpathogenic spoilage organisms, ionizing irradiation can extend the shelf life of meat food products. On December 3, 1997, FDA published a final rule (FDA Docket No. 94F-0289; 62 FR 64107) providing for the use of ionizing irradiation to control food borne pathogens and extend the shelf life of refrigerated and frozen meat food products, including uncooked meat, meat byproducts, and certain other meat food products. In this petition, FSIS is requesting that FDA permit the use of ionizing irradiation to treat these same meat food products, but in a unrefrigerated, uncooked state.

Specifically, the unrefrigerated, uncooked meat food products that could be irradiated are:

(1) The part of the muscle of any cattle, sheep, swine, or goats, which is skeletal or which is found in the tongue, or in the diaphragm, or in the heart, or in the esophagus, with or without the accompanying and overlying fat, and the portions of bone, skin, sinew, nerve, and blood vessels which normally accompany the muscle tissue and which are not separated from it in the process of dressing. It does not include the muscle found in the lips, snout, or ears. This term, as applied to products of equines, shall have a meaning comparable to that provided in this paragraph with respect to cattle, sheep, swine, and goats.

(2) The product derived from the mechanical separation of the skeletal muscle tissue from the bones of livestock using the advances in mechanical meat/bone separation machinery and meat recovery systems that do not crush, grind, or pulverize bones, and from which the bones emerge comparable to those resulting from hand-deboning (i.e., essentially intact and in natural physical conformation such that they are recognizable, such as loin and rib bones, when they emerge from the machinery) which meets the criteria of no more than 0.15 percent or 150 mg/100 gm of product for calcium (as a measure of bone solids content) within a tolerance of 0.03 percent or 30 mg.

Any part capable of use as human food, other than meat, which has been derived from one or more cattle, sheep, swine, or goats. This term, as applied to products of equines, shall have a meaning comparable to that provided in this paragraph with respect to cattle, sheep, swine, and goats. (This category of byproducts would include blood and blood plasma.)

If this petition is granted, any of the above meat food products could be treated with ionizing radiation when in a uncooked and unrefrigerated state. FSIS anticipates that initially, however, establishments are most likely to irradiate livestock carcasses or parts immediately after deboning and immediately before chilling ("hot-boned" meat). The Agency noted this in its recent proposed regulations concerning the irradiation of meat food products:

It has come to the attention of the Agency that several establishments may wish to irradiate "hot-boned" meat. Hot-boned meat is meat carcasses or parts that are deboned immediately following slaughter and then chilled. It is likely that an establishment wishing to irradiate hot-boned meat would irradiate between the deboning and the chilling of the carcasses or parts. The meat, therefore, would not have been refrigerated prior to irradiation and FDA has listed ionizing irradiation as an additive only for refrigerated or frozen, uncooked meat products. (64 FR 9092)

Hot-boned carcasses or parts are most often ground or otherwise processed into comminuted products, such as sausage, after deboning and before chilling. Establishments typically hot-bone carcasses for economic reasons. Chilling packages of comminuted meat food product is less expensive and time-consuming than chilling whole carcasses. Also, comminuted meat food products lose less weight through the dissipation of moisture during chilling than do whole carcasses.

If, under HACCP or a similar system of process controls, establishments were to irradiate hot-boned carcasses (or other unrefrigerated meat food products) prior to processing and chilling, it is likely that much of the antimicrobial effect of irradiation would be maintained throughout processing, chilling, and packaging. Under HACCP or a similar system, establishments could not use irradiation to "clean up" raw, unrefrigerated products that had been temperature abused. Notably, by early 2000, FSIS will have required all official establishments to develop and implement HACCP systems.

FSIS is requesting that FDA permit a 4.5 kiloGray (kGy) maximum dose for the irradiation of unrefrigerated, uncooked meat food products. This is the same maximum dose currently permitted by FDA for refrigerated meat food products. FSIS believes the assessment conducted by FDA regarding the safety of irradiating refrigerated meat food products is completely applicable to unrefrigerated meat food products and that the irradiation of unrefrigerated products would pose no unique risks.

Establishments that irradiate unrefrigerated meat food products would be required to meet the same requirements recently proposed by FSIS (64 FR 9089) for establishments that irradiate refrigerated or frozen, uncooked meat food products:

(C) Effectiveness of the Additive

Available scientific data indicate that ionizing radiation can significantly reduce the levels of many of the pathogenic microorganisms of concern in meat food products, including Salmonella spp., E. coli O157:H7, Clostridium perfringens, Staphylococcus aureus, Listeria monocytogenes, Campylobacter jejuni, the protozoan parasite Toxoplasma gondii, and the parasite Trichinella spiralis. The radiation dose necessary to reduce the initial population of many of the bacterial pathogens by 90 percent (the D-value, or 1-log10) ranges from 0.1 kGy to just under 1 kGy. The International Consultative Group on Food Irradiation (1996) has estimated approximate D values for some of the pathogens of concern in meat food products (Ref. 1):

PATHOGEN APPROXIMATE D-VALUES
C. jejuni 0.18 kGy
C. perfringens 0.586 kGy
E. coli O157:H7 0.25 kGy
L. monocytogenes 0.4 kGy to 0.64 kGy
Salmonella spp. 0.48 kGy to 0.7 kGy
S. aureus 0.45 kGy
T. gondii 0.4 kGy to 0.7 kGy
T. spiralis 0.3 kGy to 0.6 kGy

Given a 3:1 overdose ratio using a gamma irradiation source, a treatment achieving the proposed maximum 4.5 kGy dose could effect a 1.5 kGy minimum dose throughout palletized product. Considering the D-values above, it appears that even this minimum dose could reduce pathogens significantly (e.g., a 1.5 kGy dose could achieve an approximate 6-log10 reduction in E. coli O157:H7).

Irradiation also can significantly extend the shelf-life of meat food products through the reduction of spoilage bacteria. Andrews, et al. (1998), reviewed five studies encompassing shelf lives of different types of red meat products; the results suggest that shelf life of products treated with irradiation increase considerably compared to untreated products (Ref. 2).

Meat Product Dose (kGy) Untreated shelf life (days) Irradiated Shelf life (days)
Beef 2.5 2 – 3 9
Beef top round 2.0 8 – 11 28
Beef burgers 1.54 8 – 10 26 – 28
Beef cuts 2.0 1X 2X
Beef cuts irradiated under vacuum 2.0 NA 70
Corned beef 4.0 14 – 21 35
Lamb, whole and minced 2.5 7 28 – 35

Thayer (1993) also reports that irradiation can significantly extend the shelf-life of meat and poultry, particularly in vacuo (Ref. 3).

(D) Measuring the Quantity of the Additive

Dosimetry is the process of measuring an absorbed dose of radiation. FSIS has proposed that any official establishment irradiating refrigerated or frozen meat food products have in place a dosimetry system. FSIS would require the same for the irradiation of uncooked, unrefrigerated meat food products. Establishments would implement a dosimetry system to ensure that each lot of treated product has received the dose defined within its HACCP plan.

Under the proposed requirements, establishments that irradiate meat food products must have in place: procedures for determining the absorbed radiation dose value from the dosimeter(s); procedures for calibrating dosimeters and other means of measurement (e.g., time clocks and weight scales); procedures for ensuring specific absorbed dosages of irradiation by product unit and product lot; and procedures for verifying the integrity of the radiation source and the processing procedure. The current and proposed dosimetry requirements are based upon standards promulgated by the American Society for Testing and Materials.

It is likely that establishments will incorporate many dosimetry procedures into their HACCP plans. For example, procedures for verifying routine dosimetry (i.e., ensuring each product lot receives the total absorbed dose) could be incorporated into a HACCP plan as critical limits for the irradiation process. Also, calibration of dosimeters and other instruments could be incorporated as ongoing verification activities.

(E) Safety of the Additive

In its December 3, 1997, finding, FDA concluded that the irradiation of refrigerated and frozen, uncooked meat food products within the requested processing parameters would not present toxicological or microbiological hazards and would not adversely affect the nutritional adequacy of these products. In this petition, FSIS is requesting that FDA allow the irradiation of the same products, within the same processing parameters, but in a unrefrigerated state. FSIS believes that the irradiation of unrefrigerated meat food products poses no hazards not already accounted for by FDA in its assessment of the irradiation of refrigerated meat food products.

The main factors that determine the radiation chemistry of food are: the absorbed dosage of radiation; the ambient atmosphere during irradiation (air, reduced oxygen, or vacuum); the chemical composition of the food; and the physical state of the food (solid or liquid, frozen, refrigerated, or unrefrigerated). FSIS would permit the irradiation of unrefrigerated meat food products within the same processing parameters (dosage, ambient oxygen level, etc.) as it has proposed to allow for refrigerated meat food products. Further, the chemical composition of unrefrigerated meat food products is essentially identical to that of its refrigerated and frozen counterparts. Therefore, any differences in radiation chemistry between unrefrigerated and refrigerated meat food products would result solely from their differing physical states.

Numerous sources cite differences between the radiation chemistry of refrigerated and frozen flesh foods. In its recent finding FDA explained the cause of the differences in radiation chemistry:

If all other conditions, including dose and ambient atmosphere, are the same, the extent of chemical change that occurs in a particular food in the frozen state is less than the change that occurs in the same food in the nonfrozen state. This is a result of the reduced mobility, in the frozen state, of the initial products of irradiation (free radicals, which are highly energetic, unstable molecules). Because of their reduced mobility, these free radicals tend to recombine to form the original substance rather than to diffuse through the food to react with other components of the food matrix and thereby form different substances. Thus, both the types and the amounts of radiolytic products are affected by the physical state of the food, and, for a given food, higher radiation doses are needed to effect the same degree of chemical change in frozen versus nonfrozen food. Higher radiation doses are also needed to accomplish the same antimicrobial technical effect in a frozen food versus a nonfrozen food of the same type.

(62 FR 64110)

Unlike the differences cited above, FSIS contends that any differences between the mobility of free radicals in treated refrigerated and unrefrigerated meat food product, as a result of their differing physical states, is negligible. There is no specific research comparing the mobility of free radicals in refrigerated product to that in unrefrigerated product, owing to differences in temperature. Obviously, this lack of data does not positively confirm that there would be no differences between the radiation chemistry of treated refrigerated and treated unrefrigerated product. However, there is data regarding the binding of water in meat (skeletal muscle), as well as research concerning the sensitivity of pathogens to irradiation as affected by product temperature, that indirectly supports our assertion.

Water Binding in Meat

Water composes from 65 to 80 percent of meat (Ref. 4). When irradiated, this water can form a number of products, including hydroxyl radicals, hydrated electrons, hydrogen atoms, hydrogen molecules, hydrogen peroxide, and hydrogen proteins (Ref. 5). Each of these products of water radiolysis can react with other meat components, and primarily with carbohydrates and proteins, to form further radiolytic products (see Ref. 5). As explained above, the amount of radiolytic products produced is partially dependent on the mobility of the initial water radicals formed, that is, whether the irradiated product is frozen or nonfrozen. Again, FSIS asserts that there would be no significant difference between the mobility of water radicals in unrefrigerated and refrigerated meat as a result of differences in temperature.

There may be a slight difference in the amount of water available for radiolysis in fresh, pre-rigor meat than would be available in chilled or aged, post-rigor meat. Of the total water in fresh muscle meat, 4 to 5 percent is tightly bound to electrically charged reactive groups on muscle proteins (see Ref. 4). Other water molecules are attached to the bound molecules in layers (immobilized water). These layers become weaker as the distance from the muscle proteins becomes greater. Bound and immobilized water, however, constitute only a small percentage of the total water in meat. Most of the water molecules are free and held to the meat by surface forces (see Ref. 4).

During the postmortem period, as product pH drops due to the formation of lactic acid and as the onset of rigor mortis brings about certain protein interactions, the water binding properties of meat lessen considerably (see Ref. 4). Very small amounts of water (between 1 and 3 percent) may be lost from meat carcasses as they are chilled, aged, or processed. We can assume, therefore, that less water may be available for radiolysis in refrigerated meat than in unrefrigerated meat. Therefore, the chemical effect of ionizing radiation on unrefrigerated meat may be somewhat greater. FSIS contends however, that these theoretical differences would be immeasurable.

Pathogen Reduction resulting from Irradiation as Affected by Product Temperature

The availability of water for radiolysis can heavily impact the antimicrobial effects of ionizing radiation. Thayer and Boyd have conducted studies on the sensitivity of E. coli O157:H7 and Listeria monocytogenes in meat to irradiation, as affected by product temperature (Refs. 6 and 7). In both studies, Thayer and Boyd reported that, given identical processing conditions, there is a linear increase in pathogen reduction resulting from the irradiation of frozen meat as the product temperature increased toward 0 C. At product temperatures between 0 and 15 C, however, the level of pathogen reduction flattened out. In both studies, the authors attributed the majority of pathogen reduction to the increased mobility of water radicals (primarily OH.) resulting from the rising product temperatures.

We can conclude, therefore, that there is little variation in the mobility of water radicals in meat at temperatures between 0 C (the lower end of refrigeration temperatures) and 15 C (the beginning of the temperature range for "hot-boned" product). As radiation chemistry is greatly influenced by the mobility of water radicals, we can further conclude that there is little difference between the radiation chemistry of refrigerated and unrefrigerated meat.

Conclusion

Any variations in the radiation chemistry of meat food products that result from differences in product temperature during treatment would be insignificant and immeasurable. The irradiation of unrefrigerated meat food products within the parameters already allowed by FDA for refrigerated meat food products would pose no additional toxicological or microbiological hazards nor effect the nutritional adequacy of the treated products. FDA’s assessment of the irradiation of refrigerated meat food products is completely applicable to the irradiation of unrefrigerated meat food products.

REFERENCES

1. International Consultative Group on Food Irradiation, Irradiation of red meat: A compilation of technical data for its authorization and control, August 1996.

2. Andrews, L.S., et al., "Food Preservation Using Ionizing Radiation," Review of Environmental Contaminant Toxicology, Vol. 154, 1998.

3. Thayer, Donald W., "Extending Shelf Life of Poultry and Red Meat by Irradiation Processing," Journal of Food Protection, Volume 56, 1993.

4. Forrest, John C., et al., "Properties of Fresh Meat," in Principles of Meat Science, W.H. Freeman and Co., 1975, p. 77.

5. World Health Organization, "Chemistry of Food Irradiation," in Safety and nutritional adequacy of irradiated food, 1994.

6. Thayer, Donald W. and Glenn Boyd, "Elimination of Escherichia coli O157:H7 in Meats by Gamma Radiation," Applied and Environmental Microbiology, Volume 59, 1993.

7. Thayer, Donald W. and Glenn Boyd, "Radiation Sensitivity of Listeria Monocytogenes on Beef as Affected by Temperature," Journal of Food Science, Volume 60, 1995.

Note: Copies of the reference articles are available for viewing in the FSIS Docket Room. The articles will not be made available on this Web site due to copyright restrictions.

 

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For Further Information Contact:
DANIEL L. ENGELJOHN, Ph.D.
Director, Regulations and Directives Development Staff
Food Safety and Inspection Service, USDA
Phone: (202) 720-5627
Fax: (202) 690-0486
E-mail: daniel.engeljohn@usda.gov