Irradiation of Prepackaged Food: Evolution of the ... - ACS Publications

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Chapter 12

Irradiation of Prepackaged Food: Evolution of the U.S. Food and Drug Administration's Regulation of the Packaging Materials Kristina E. Paquette Office of Food Additive Safety, U.S. Food and Drug Administration, 5100 Paint Branch Parkway, MS HFS-275, College Park, MD 20740

The F D A approved the first materials intended for use as packaging for irradiated foods (polyolefin films, polystyrene, cellophane, vinylidene chloride copolymers, and others) in 1964. Several other materials were approved for this use during the next four years. Since then, only one material, ethylene vinyl acetate copolymer, was added to Title 21 of the Code of Federal Regulations, in 1989. The recent interest in irradiating meat to eliminate pathogens such as E. coli O157:H7 has resulted in several industry submissions to the Agency regarding new packaging materials, as well as the radiation sources, intended for use during the irradiation of prepackaged food. A brief history of F D A regulation of packaging materials irradiated in contact with food, including a discussion of human exposures to radiolysis products formed in irradiated polymers, will be presented. The evaluation of new packaging materials for irradiated foods will be discussed within the context of F D A ' s Food Contact Substance Notification Program.

182

U.S. government work. Published 2004 American Chemical Society


183 In the 1960s, the F D A approved many packaging materials for use during the irradiation of prepackaged food with only two additional materials receiving approval since (see below for details). Most of the approvals were obtained by the U.S. Army and the U.S. Atomic Energy Commission (AEC) (/). These agencies shared responsibilities under the U.S. Government's Atoms for Peace program to develop peaceful uses for nuclear technology. The U.S. Army was particularly interested in radiation-sterilization to add to the arsenal of methods for producing shelf-stable foods for the military (2, 5). Why, after 40 years, is there sudden industry interest in obtaining F D A approval for new packaging materials for use during the irradiation of prepackaged food that is intended for consumption by the general public? The answer can be summed up in two words: emerging pathogens. The following timeline illustrates increasing concern about pathogens and interest in new technologies, such as irradiation, for reducing pathogen levels in meat and poultry: 1982 E. coli 0157:H7 was first linked to serious illness from eating undercooked meat (4). 1990 The F D A approved the irradiation of fresh or frozen uncooked poultry at doses up to 3 kGy in response to food additive petitions (FAP) submitted by the U.S. Department of Agriculture and Radiation Technology, Inc. (5). The impetus for these petitions was a heightened awareness of the threat to public health from food-borne illnesses caused by Salmonella, Yersinia, and Campylobacter on poultry. 1993 The widely publicized Jack-in-the-Box incident occurred in which numerous illnesses and four deaths, primarily among children, were caused by E. coli 0157:H7 present in undercooked hamburgers served at the fast food chain in four states of the Western U.S. (4, 6). 1997 In response to a petition submitted by Isomedix, Inc., the F D A approved the irradiation of uncooked meat at doses up to 4.S kGy for refrigerated products and up to 7.0 kGy for frozen products (7). 2001 In response to a petition submitted by the National Center for Food Safety and Technology, Illinois Institute of Technology (NCFST), the F D A deemed that the three radiation sources permitted for use on food, gamma, X-ray, and e-beam, are equivalent in terms of the types and levels of radiolysis products (RP) generated in the packaging materials under the conditions at which prepackaged foods are irradiated (8). This decision 1

1

The Gray (Gy) is a unit of radiation-absorbed dose that equals the amount of energy absorbed per unit mass of a material during irradiation (1 Joule/kg). 10 kGy = 1 Megarad (Mrad), a previous unit of absorbed dose.

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expanded the combinations of packaging materials and radiation sources that may be used on food. The list of FDA-approved materials does not adequately cover the expansive number of polymers, adhesives, and colorants that are used in multi layer, multi-constituent food-packaging materials that offer special properties such as an improved oxygen barrier. In addition, very few of the adjuvants (e.g., antioxidants, plasticizers, and antifogging agents) that are routinely used in today's materials have been evaluated and approved by the F D A for use in packaging materials that are intended to be irradiated in contact with food.

Legal Considerations: Why Is FDA Approval Necessary?

Background The Federal Food, Drug, and Cosmetic Act (or the "Act"), Section 409(a), states that the use of a food additive shall conform to a regulation prescribing the conditions under which the additive may safely be used. Section 201(s) of the Act defines a food additive, in part, as "any substance the intended use of which results or may reasonably be expected to result, directly or indirectly, in its becoming a component or otherwise affecting the characteristics of food." The definition encompasses packaging because packaging components could become a component of food by migrating from the packaging into food. In the past, packaging components have been referred to as "indirect additives" because these substances are not added directly to food for some functional purpose. Section 201(s) also defines any source of radiation intended for use on food as a food additive. Under Section 409 of the Act, as originally established, food additives require premarket approval by the F D A through the submission of a food additive petition and publication of a regulation authorizing their intended use. The requirements for a petition are described in Title 21 of the Code of Federal Regulations (CFR), Part 171.1 (Petitions) (9). F D A ' s safety evaluation of a food additive includes a dietary exposure assessment and a toxicological evaluation based on animal feeding studies and other toxicological information. Recently, Section 309 of the F D A Modernization Act of 1997 ( F D A M A ) amended Section 409 of the Act to establish a new process, referred to as the food contact notification (FCN) process, as the primary method of authorizing new uses of food additives that are food contact substances (FCS). Section 409(h)(6) defines an FCS as "any substance intended for use as a component of materials used in manufacturing, packing, packaging, transporting, or holding


185 food i f such use is not intended to have any technical effect in such food." The requirements for an F C N are described in 21 CFR 170, Subpart D (Food Additives - Premarket Notifications) (9), and guidance documents are available on F D A ' s website (10). Because the safety standard is the same for all food additives, the data and information requirements for FCNs and petitions are comparable. There are two main differences in the petition and F C N processes. First, in contrast to the petition process, the F C N process will not result in a food additive listing in the CFR authorizing the use for any manufacturer of the FCS. Rather, an F C N for a food contact substance cannot be effective for anyone other than the manufacturer identified in the F C N . F D A maintains a list of effective FCNs on its website (70). Second, under the F C N process, the F D A has 120 days in which to object to an F C N or the F C N becomes effective, and the FCS may be legally marketed for the intended use.

Irradiated Packaging A reference list of materials currently permitted for use during the irradiation of prepackaged food is given in Table I. With the exception of polystyrene (PS) foam trays, all the materials in Table I are listed in 21 CFR 179.45 (Packaging materials for use during the irradiation of prepackaged food) (9). The PS foam trays were reviewed under F D A ' s Threshold of Regulation policy, which exempts certain food additives from a food additive regulation listing when the use results in a dietary concentration (DC) of less than 0.5 ppb (see 21 CFR 170.39 (9)). In addition to §179.45, two other sections of the CFR are applicable to the irradiation of prepackaged food: §179.26 (Ionizing radiation for the treatment of food) and § 179.25(c) (General provisions for food irradiation). Section 179.26 lists the radiation sources that may be used on food, the specific foods that may be irradiated, the conditions under which those foods may be irradiated, and the labeling that is required on irradiated foods. Section 179.25(c) inextricably links the packaging materials listed in §179.45 with the conditions of use described in §179.26, meaning that no other packaging materials (including adjuvants) are permitted for prepackaging food that will be irradiated. The finished packaging material and all adjuvants must meet any specifications and limitations of the applicable regulations in order to be marketed in the U.S. for food contact. Although the vast majority of food contact substances are evaluated via the F C N process, it is still possible that an F C S might require evaluation via the petition process, especially if its dietary concentration is exceptionally high (on the order of 1 ppm or higher; see §170.100(c)(1)) (9). The F C N process can take much less time than the petition process because of the additional time

186 Table I. Materials Currently Permitted for Use During Irradiation of Prepackaged Food


Year 1964

Regulation § 179.45(b)

Material Nitrocellulose-coated cellophane Glassine paper Wax-coated paperboard Polyolefin film Polystyrene film Rubber hydrochloride film Vinylidene chloride-vinyl chloride copolymer film Vinylidene chloride copolymer-coated cellophane Vegetable parchments Kraft paper to contain only flour Polyethylene film Polyethylene terephthalate (PET) film Nylon 6 film Vinyl chloride-vinyl acetate copolymer film Optional adjuvants for polyolefin films plus optional vinylidene chloride copolymer coating PET film plus optional adjuvants, vinylidene chloride copolymer and polyethylene coatings Nylon 11 Ethylene-vinyl acetate copolymers Polystyrene foam tray 8

a

8

Requester AEC

Max. Dose (kGy) 10

AEC AEC AEC AEC AEC AEC

10 10 10 10 10 10

AEC

10

U.S. Army U.S. Army

60 0.5

U.S. Army U.S. Army

60 60

U.S. Army U.S. Army

60 60

AEC

10

AEC

10

AEC Cryovac

10 30

Amoco

7.2

8

1965

§179.45(b)

1967

§ 179.45(d) §179.45(b) 1179.45(d)

8

8

8

8

1968

a

§179.45(b)

1989

§ 179.45(c)

1996

Threshold of Regulation submission

Plus limited optional adjuvants.

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needed to prepare and publish a regulation in response to a petition. The Threshold of Regulation policy (described above) is another route to F D A approval of new FCSs.

Exposure to Radiolysis Products from Currently Regulated Packaging Materials In order to approve NCFST's petition regarding the equivalency of the three radiation sources that may be used on prepackaged food (see the timeline above), it was necessary to reevaluate the dietary exposure to RPs formed in the packaging materials currently listed in §179.45 for the following reasons: •

Approximately 40 years had passed since F D A first evaluated the materials.

•

Several modern analytical methods, e.g., gas chromatography (GC) with mass spectrometry detection, became commercially available in the early 1970s, making it possible for the first time to obtain rapid, quantitative results for numerous individual organic chemicals (77). These types of data, particularly for volatile RPs, were not available when F D A first evaluated the materials.

•

Over the years, F D A has developed new methods for calculating dietary exposure to FCSs that incorporate marketing data for specific types of foodpackaging materials and the types of food that are packaged in them (72). Exposure estimates based on consumption factors (CF), which are the fraction of all food in the daily diet that contacts a particular type of packaging material, and food-type distribution factors (f ), which are the fraction of food packaged in a particular packaging material that is aqueous, acidic, alcoholic, or fatty, are more realistic than those generated in the 1960s. T

•

It was necessary to determine if there would be any increase in dietary exposure to RPs formed in the packaging materials if all three radiation sources could be used on all the packaging materials currently listed in §179.45.

Relevant Parameters The first step in evaluating exposure to RPs from packaging materials was to identify and quantify parameters that depict the conditions under which prepackaged food would be irradiated and stored. Based on an extensive review

188 of the literature, the following six parameters were determined to be relevant to R P formation in polymers:


Absorbed Dose Irradiation leads to two competing reactions in polymers: chain scission, which leads to the formation of low-molecular-weight RPs, and crosslinking, which can lead to a decrease in residual oligomers (13, 14, 15). A n increasing absorbed dose can lead to crosslinking up to an optimum point. If the dose is increased beyond that point, chain scission becomes dominant. In the absence of crosslinking, which occurs only in an 0 -free atmosphere (see below), concentrations of RPs generally increase linearly with absorbed dose within limited dose ranges that include the ranges needed for irradiating foods (13, 14, 15,16). Because fresh or frozen poultry, fresh meat, and frozen meat may be irradiated to doses up to 3, 4.5, and 7.0 kGy, respectively, and because only a few foods of limited consumption may be irradiated to higher doses, 10 kGy was selected as a conservative value for use in exposure estimates for polymer RPs that form in foods irradiated in their final packaging. 2

2

Atmosphere In the presence of oxygen or air (21% 0 ) , polymer chain scission leads to the formation of oxidative degradation products, which are primarily oxygenated volatile and semi-volatile organic compounds such as aldehydes, ketones, and carboxylic acids (13, 15, 17, 18, 19, 20, 21, 22). Crosslinking dominates under vacuum or an inert atmosphere. In air, increasing dose leads to higher concentrations and a wider variety of measurable RPs (21). For example, for low-density polyethylene (LDPE) irradiated to 20 kGy with an e-beam source at room temperature, the levels of oxygenated volatile and semi-volatile organic compounds are about one order of magnitude higher in polymer samples irradiated in air than in those irradiated in a vacuum, while the levels of hydrocarbons are the same in the presence or absence of O2 (17). In the U.S., all commercial facilities that irradiate food and other bulk materials such as medical supplies are currently irradiating in air (23, 24, 25). If the food is packaged in a material that contains an oxygen barrier and the interior 2

2

Dry enzyme preparations may be irradiated to 10 kGy, dry spices to 30 kGy, and frozen, packaged meats used solely in N A S A space flight programs to 44 kGy (see §179.26).

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is purged of oxygen, then oxygenated RPs are not likely to form in the packaging layers inside that barrier or in the food. However, if the interior is not completely purged of oxygen, RPs may form in the inner layers of the packaging material and migrate to the food.

Dose Rate In the presence of air, for a given dose, the low dose rates typical for gamma sources can lead to levels of RPs in polymers that are higher than levels generated at the higher dose rates typical for X-ray and e-beam sources; the latter, for a given dose, also result in the formation of fewer types of detected RPs (13, 15, 17, 19, 20, 22, 26). Exposure data based on studies of migrants from polymers irradiated by gamma sources can therefore be considered conservative for migrants formed by any source of radiation. The difference between the levels of RPs generated by gamma and e-beam sources is generally not great at doses below 20 kGy (20). For L D P E irradiated to 20 kGy in air at room temperature, the levels of RPs induced by gamma radiation exceed those induced by e-beam radiation only by about a factor of two (17). Therefore, when gamma irradiation data are unavailable, it is reasonable to use the levels of RPs generated by e-beam or X-ray sources to estimate exposures at low doses (

Irradiation of Prepackaged Food: Evolution of the ... - ACS Publications

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