Evaluating Packaging Materials for Use during the Irradiation of

Chapter 12

Evaluating Packaging Materials for Use during the Irradiation of Prepackaged Food Downloaded by UNIV DE SHERBROOKE on May 3, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2014 | doi: 10.1021/bk-2014-1162.ch012

Vanee Komolprasert* Division of Food Contact Notifications, Office of Food Additive Safety, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, College Park, Maryland 20740 *E-mail: [email protected].

Irradiation is an effective means for controlling foodborne pathogens and has gained much interest from the food industry in the past two decades. Irradiation of prepackaged food is a reasonable and practical method to avoid the post-irradiation contamination of food, and additionally, the irradiated foods are ready for shipping to the market immediately after irradiation. Irradiation can induce chemical changes to the packaging materials resulting in the formation of breakdown products that may readily migrate into foods. Therefore, the packaging materials holding food being irradiated are required to undergo premarket authorization prior to use. This chapter addresses the interpretation of the food irradiation regulations, the effects of various types of radiation on food packaging materials, challenges for analyzing breakdown products, and some approaches for use in evaluating packaging materials for use during the irradiation of prepackaged food.

Not subject to U.S. Copyright. Published 2014 by American Chemical Society In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.

Downloaded by UNIV DE SHERBROOKE on May 3, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2014 | doi: 10.1021/bk-2014-1162.ch012

Introduction The U.S. Food and Drug Administration is responsible for regulating the use of irradiation in the treatment of food and food packaging. This authority results from the 1958 Food Additives Amendment to the Federal Food, Drug, and Cosmetic Act (FD&C Act) where Congress explicitly defined a source of radiation as a food additive (Section 201(s) of the FD&C Act). Section 201(s) of the FD&C Act, defines a food additive 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 any food……including any source of radiation intended for such use…” The 1958 Food Additives Amendment also provides that a food is adulterated (that is, it cannot be marketed legally) if it has been irradiated, unless the irradiation is carried out in conformity with a regulation prescribing safe conditions of use (Section 403(a)(7) of the FD&C Act). Prior to 1999, FDA regulated the lawful use of irradiation of food packaging materials through the food additive petition (FAP) process, the completion of which resulted in the promulgation of a regulation published in the Federal Register prescribing the approved use. Since 1999, food additives, including radiation, are authorized by the food contact notification (FCN) process as described in 21 CFR §170.100–§170.106 or threshold of regulation (TOR) exemption processes as described in 21 CFR §170.39. When pre-packed food is irradiated, the packaging materials holding the food are also irradiated together with food, and as such these packaging materials are required to undergo a safety evaluation before they can be used to hold irradiated food. The safety evaluation for the packaging materials relies on an assessment of the radiolysis products (RPs) that are formed and which may migrate to the packaged food. Under Section 409(a) of the Act, a food is deemed adulterated, and thus prohibited from interstate commerce, if it has been intentionally irradiated, unless the irradiation is carried out in compliance with an applicable food additive regulation or effective FCN or is exempted from the requirement of a listing regulation under the TOR exemption process for the specified conditions of use. This chapter highlights answers to questions regarding food irradiation, irradiation regulations, effects of radiation on food packaging materials, challenges in analyzing radiolysis products, and approaches that may be considered in evaluating packaging materials for use during the irradiation of prepackaged food.

Why Is There Interest in Food Irradiation? Although food irradiation technology has been utilized for several decades in many other countries, its use in the U.S. became more prevalent by the food industry in 1990’s after the incessant outbreaks of food-borne pathogens that led to many food-borne illnesses (1). Irradiation is an effective means of controlling several food-borne pathogens on/in various foods thereby improving the safety of food and extending shelf life (2). Several types of foods are currently permitted to be irradiated with ionizing radiation and are listed under Title 21 of Code of 120 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.


Federal Regulations (denoted 21 CFR) section 179.26 (Ionizing radiation for the treatment of food) (3). Since 1997 the list has expanded to include refrigerated and frozen uncooked meat products, fresh shell eggs, seeds for sprouting, fresh and frozen molluscan shellfish, and most recently, fresh iceberg lettuce and fresh spinach. Foods are preferably prepackaged before irradiation to avoid recontamination, and after irradiation, the irradiated foods are immediately ready to be shipped to the market. However, to ensure food safety, the packaging materials must not be altered upon irradiation in a manner that could result in any substance in the packaging becoming a component of food at unsafe levels.

What Are the Food Irradiation Regulations? The food irradiation regulations are codified in accordance with the interpretation of the definition of a food additive, as previously mentioned, by which both foods and food packaging materials that are exposed to ionizing radiation are required to undergo premarket approval to ensure the safety of the irradiated foods. 21 CFR Part 179 (Irradiation in the production, processing and handling of food) consists of Subparts B and C. Subpart B (Radiation and Radiation Sources) includes section 179.26 (denoted as §179.26) that describes radiation or energy sources, conditions of irradiation and a list of foods permitted for irradiation, and labeling. Section 179.25 (General provisions for food irradiation) links food packaging materials as specified in §179.45 to the conditions of irradiation as described in §179.26. Subpart C (Packaging Materials for Irradiated Foods) includes §179.45 (Packaging materials for use during the irradiation of prepackaged foods) and describes approved polymers and adjuvants. Foods that are not yet permitted to be irradiated as described in 21 CFR §179.26 need to undergo premarket approval via the food additive petition (FAP) process, the completion of which results in the promulgation of a regulation published in the Federal Register prescribing the approved use. Food packaging materials not yet listed in 21 CFR §179.45 need to undergo premarket approval via the FCN or TOR exemption process as noted above.

What Food Packaging Materials Are Already Permitted for Holding Food during Irradiation? There are several food packaging materials permitted for use in contact with foods during the irradiation process and they are listed in 21 CFR §179.45 (Packaging materials for use during the irradiation of pre-packaged foods). The list is not comprehensive as it only contains a limited number of packaging materials, such as films, homogeneous structures, and some adjuvants that they may contain. Packaging that is constructed from these materials may be irradiated by any permitted radiation source (gamma rays, electron e-beams, or X-rays), in either the presence or absence of oxygen, and in contact with food under the defined radiation conditions (e.g., a maximum dose limit). For example, approved 121 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.


films include polyolefin films complying with 21 CFR §177.1520 (Olefin polymers); polyethylene terephthalate (PET) films complying with 21 CFR §177.1630 (Polyethylene phthalate polymers), subparagraphs (e)(4)(i) and (ii); Nylon 6 films complying with 21 CFR §177.1500 (Nylon resins), subparagraph (a)(6); and ethylene vinyl acetate copolymers complying with 21 CFR §177.1350 (Ethylene-vinyl acetate copolymers). Keep in mind that the §179.45 list has not been updated since the 1980’s, nor does it include modern food packaging materials that are more desirable for use in contact with food during irradiation. Food packaging materials not listed in §179.45 are required to undergo premarket approval via the FCN process as described in 21 CFR §170.100-§170.106, or the TOR exemption process as described in 21 CFR §170.39. Regardless of the regulatory approval process, the safety assessment for packaging materials used to hold food during irradiation is conducted in accordance with FDA recommendations as described in the chemistry, toxicology and environmental guidance documents published by the agency (4). Although there are no effective FCNs for packaging materials that have been authorized for use in irradiation of prepackaged foods, a number of significant authorizations have been granted via the TOR exemption process. TOR exemptions have been issued to permit the irradiation of certain packaging structures under specific conditions of use, i.e., under an oxygen free environment, a nitrogen atmosphere, or while frozen and under vacuum. TOR exemptions granted in 2005 permitted use of polystyrene (PS) foam trays with multilayer food contact coatings for contact with ground beef being irradiated in a nitrogen atmosphere, or under vacuum while frozen, at doses not to exceed 3.0 kGy. The most recent TOR exemptions in 2010 (5) permitted all food additives (i.e., food contact substances) listed in 21 CFR §174–186, effective FCNs, and TOR exemptions, for contact with foods being irradiated in a verifiably oxygen-free environment or while frozen and contained under vacuum, at doses not to exceed 4.5 kGy.

If Food Packaging Materials Are Irradiated before Food Contact, Are They Required to Undergo Premarket Approval? Irradiation of food packaging materials before food contact is allowed only if the irradiation is considered as part of the manufacturing process (i.e., for cross-linking or sanitizing purposes), provided that the packaging materials are either listed in 21 CFR §179.45 or have been otherwise approved for non-irradiated uses. The irradiation process must be performed under conditions of good manufacturing practice (GMP), and the irradiated packaging materials must comply with the specifications and limitations as described in all applicable authorizations. This implies that the irradiation does not significantly affect the packaging materials, i.e., does not form significant amounts of new chemical substances that could migrate to food. 122 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.

The irradiated packaging materials must also comply with the general provisions in 21 CFR §174.5. For example, any substance used as a component of food contact articles must be of a purity suitable for its intended use, used in accordance with section 402(a)(3) of the FD&C Act, and use of the irradiated packaging material should not impart odor or taste to food rendering it unfit for human consumption.


What Are Radiation-Induced Changes in Polymeric Food Packaging Materials? It is generally known that radiation induces chemical changes in polymeric packaging materials which could result in formation of unique radiolysis products in polymers. The chemical changes are induced by two competing reactions – cross-linking and chain scission/degradation. Both reactions are random and are proportional to the dose, dose rate and oxygen content of the atmosphere in which the polymer is irradiated. Generally, cross-linking dominates when polymers are irradiated under vacuum or in an inert atmosphere such as nitrogen, which is the basis for approving the recent TOR exemptions (5). Chain scission dominates when polymers are irradiated in the presence of oxygen, resulting in the formation of oxidative degradation products, or oxidative RPs (ORPs), which are primarily oxygenated volatile and semi-volatile organic compounds. The concentrations of these compounds generally increased with increased radiation dose. The radiation-induced changes in functionality and properties of packaging materials have been investigated using mechanical and physicochemical testing, colorimetry, Fourier transform infrared spectroscopy (FTIR), rheological testing, and electron spin resonance (ESR) spectroscopy. A review of these reactive changes is available (6).

How To Determine if Radiolysis Products (RPs) Are Formed from Polymers and Adjuvants? The best method to determine if there are RPs present in irradiated packaging materials, originating from either the polymer and/or adjuvants, is by conducting an irradiation experiment with the materials and then comparing the irradiated materials with their non-irradiated counterparts. Any RPs generated would then be the subject of safety assessment for a new use. In performing the safety assessment for a new use, the dietary exposure to RPs must be considered in context with the available toxicological information on the RPs. The residual levels of RPs are important for estimating exposures using the simple assumption of 100% migration to food and known thickness, density, food mass-to-surface area ratio, and the consumption factor (CF) for the packaging application. If the dietary concentration (DC) of any one RP exceeds 0.5 µg/kg, other approaches, such as migration modeling or a migration study, may be used as the next step to refine the exposure. 123 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.


What Information Is Recommended To Submit to FDA in Support of the Irradiation of Packaging Materials in the Presence of Oxygen? When searching for regulatory precedent, keep in mind that there are not many approvals for the use of the irradiation of packaging materials in the presence of oxygen because not many requests have been submitted to FDA. The approval process might be more difficult due to the complexity of analyzing for the identities and amounts of all ORPs. Since chain scission reactions dominate when polymers/adjuvants are irradiated in the presence of oxygen, ORPs are of safety concern and should be evaluated for determining whether the packaging materials are suitable for use during the irradiation of prepackaged food that requires oxygen to maintain quality (e.g., fresh produce). The ORPs include new substances and existing substances that increase in concentration, such as aldehydes, ketones, alcohols, carboxylic acids, all of which are known to affect the organoleptic properties and shelf-life of irradiated foods.

What Analytical Approaches May Be Considered for Testing Irradiated Packaging Materials? A real-life or practical approach may be considered for use in testing the irradiated packaging materials. A “real-life” approach involves irradiating the polymer while in contact with a food simulant. The RP migration levels in the simulant are used in estimating exposure. However, this method may be difficult in practice due to analytical problems with small quantities of RPs generated from the food simulant that interfere with the RPs that migrate from the polymer to the simulant. On the other hand, a practical (or step-wise) approach involves irradiating the polymer alone, followed by analysis of residual RPs by an appropriate method and properly validated procedure. The step-wise approach is intended to pre-identify and quantify low molecular weight (volatile) RPs present in irradiated polymer samples, using headspace/gas chromatography (HS/GC) or thermal desorption, with mass spectrometry (MS) detection. Non-volatile RPs are usually analyzed by total polymer dissolution or solvent extraction, followed by liquid chromatography (LC) with MS detection. After the RPs are identified and quantified in the polymer, the concentration of each RP may be used to calculate exposure based on an assumption of 100% migration to food. If the assumed 100% migration level produces RP exposures that are too high to be supported by toxicology data, a more realistic level of migration may be estimated by migration modeling. As an alternative, a migration study with food-simulating solvents or actual foods may be conducted under realistic use conditions, to refine the exposure estimate. If a migration study is needed, consult the recommendations on migration testing as described in Chemistry Guidance, which can be accessed from the Internet in the Ingredients, Packaging & Labeling section under the Food topic of www.fda.gov. 124 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.

Another approach is to conduct a direct migration study, skipping the pre-identification step as describe above. However, this alternate approach is not informative because it does not pre-identify the RPs, an essential step in developing appropriate methods for quantification of the RPs. The drawbacks of the approach are concerns on stability of RPs in the food simulants, the increased possibility that RPs could be missed completely, and it is very difficult to validate the analytical results.


What Are Special Considerations on Polymer Adjuvants? Most polymers commonly contain adjuvants, such as antioxidants and stabilizers that enhance polymer processing. Although the §179.45 contains various approved polymers, only few adjuvants are approved (6). The lack of approved adjuvants presents a challenge for the use of packaging materials during the irradiation of prepackaged food. Upon irradiation of a polymer-adjuvant system in the presence of oxygen, adjuvants preferentially degrade over polymers (7), resulting in high levels of adjuvant RPs in comparison to polymer RPs. Fortunately, adjuvant RPs may be predicted from their chemical structure or previous studies discussed in the literature. If an adjuvant is not yet approved for non-irradiated uses, additional testing may be needed for both the non-irradiated and irradiated uses.

How Would Radiolysis Products from Adjuvants Be Predicted or Identified? RPs may be predicted using a model polymer system instead of a real polymer system to simplify analytical work. Also, a thermal degradation experiment may assist in determining the RPs because it has been reported that irradiation is comparable to accelerated aging by photochemical and/or thermal oxidation (6). Thus, a thermal degradation experiment can be supplemental to an irradiation experiment. Moreover, adjuvant RPs may be identified using mass spectrometry (MS). If the cone voltages (collision energy) of MS is set to match the energy (irradiation dose) delivered to the adjuvant, then it may be possible to use the mass spectra for the adjuvant to determine the likelihood of fragments that may be formed from its oxidation (6).

Conclusion The U.S. Food and Drug Administration is responsible for regulating the use of irradiation in the treatment of food and food packaging materials. Several food packaging materials that are subjected to irradiation incidental to the radiation treatment and processing of prepackaged foods are listed in 21 CFR §179.45. Additional food packaging materials that are recently approved via a TOR exemption expands the 21 CFR §179.45 list to include all authorized FCSs for use in articles to be irradiated, incidental to the radiation of prepackaged foods, when the process meets 21 CFR §179, at doses not to exceed 4.5 kGy, 125 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.

under an oxygen-free environment or while frozen and contained under vacuum. Packaging materials that are not yet authorized for holding food during irradiation require premarket approval via the FCN or TOR exemption process. Evaluating the suitability of packaging materials, in particular those that require oxygen to maintain food quality, relies on the identities, quantities and dietary exposures to the RPs. A step-wise approach as described in this chapter is recommended for ORPs. However, the agency is always open to receiving new approaches for the analysis of RPs.


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Center for Disease Control and Prevention, June 21, 2103; URL http://www.cdc.gov/foodborneburden/2011-foodborne-estimates.html, accessed November 25, 2013. Morehouse, K.; Komolprasert, V. In Irradiation of Food and Packaging: Recent Developments; Komolprasert, V., Morehouse, K., Eds.; ACS Symposium Series 875; American Chemical Society: Washington, DC, 2004; pp 1−11. Electronic Code of Federal Regulations; U.S. Government Printing Office, Title 21, Part 179; URL http://www.ecfr.gov/cgi-bin/textidx?c=ecfr&sid=d36753bca57802e9889f3bc4f277c77e&rgn=div5&view =text&node=21:3.0.1.1.10&idno=21#21:3.0.1.1.10.2.1.3, accessed November 21, 2013. U.S. Food and Drug Administration, Guidance. Food Contact Notification Program; URL http://www.fda.gov/Food/IngredientsPackagingLabeling/ PackagingFCS/default.htm, accessed November 25, 2013. U.S. Food and Drug Administration. Threshold of Regulation Exemptions; URL http://www.fda.gov/Food/IngredientsPackagingLabeling/ PackagingFCS/ThresholdRegulationExemptions/ucm093685.htm, accessed November 25, 2013. Komolprasert, V. In Food Irradiation Research and Technology, 2nd ed.; Sommers, C. H., Fan, X. Wiley-Blackwell Publishing: New York, 2013; pp 147−168. Paquette, K. In Irradiation of Food and Packaging: Recent Developments; Komolprasert, V., Morehouse, K., Eds.; ACS Symposium Series 875; American Chemical Society: Washington, DC, 2004; pp 182−202.

126 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.

Evaluating Packaging Materials for Use during the Irradiation of

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