Additives in food packaging

In the United States, food packaging materials, including additives in the polymers, are regulated by the U.S. Food and Drug Administration (FDA). Jennifer Markarian reports for Plastics Additives & Compounding on a change in the FDA approval system and summarizes trends in food packaging additives such as slips, antistats, antioxidants, colorants, antifogs, antimicrobials and oxygen scavengers in the USA.

Changes in FDA regulations

FDA requirements vary with the end-use of the packaging material, such as type of food that will be contacted and usage temperature. To gain direct food contact approval, materials must meet extractability requirements. Although regulations are vague in some areas, “the general principle is that no matter what is in the packaging, it must not adulterate the food,” explains Dr. Robert Bussey, Regulatory Services Project Manager at The National Food Laboratory in Dublin, California.

A significant change in the FDA approval procedure was instituted in January 2000 with the new Food Contact Notification (FCN) system. To get approval for a new food-contact substance (FCS), the producer submits information including composition; intended use including additive level, usage temperature and type of food the substance will contact; and data on migration of the substance into food.

Migration studies can use food-simulating solvents, such as 10% ethanol to represent aqueous, acidic and low-alcohol foods, or a food oil or 50 or 95% ethanol to represent fatty foods, explains Dr. Bussey. Experimental temperature and duration are set at the most extreme anticipated conditions. “For example, the most extreme condition requires heating at 121°C (250°F) for two hours, followed by 10 days at 40°C (104”F), in a special cell designed to withstand the extremes of temperature and pressure,” notes Dr. Bussey. The FDA uses migration data to estimate consumer exposure to the substance. In the previous system, an application could take years to gain approval. With the FCN system, the FDA has 120 days to review the application and object based on safety grounds, or the substance may be marketed. Expectations were that the new system would result in many more applications for new products from companies that otherwise would not have tried marketing in food applications, but it is too early to tell how much impact the new system has had, comments Steve Hentges at American Plastics Council. Companies such as GE Specialty Chemicals that are using the new system report that the clearly articulated timetable makes the process much easier. The FCN system “is economically attractive to companies since the use of the clearance is limited to the notifying company,” adds Naeem Mady of Ciba Specialty Chemicals.

Although food companies have been driving a trend towards irradiation to prolong shelf life, general FDA guidance on package irradiation has not yet been published. The FDA does give advice to companies about specific irradiation questions. Only a few polymers are approved for gamma irradiation of prepackaged food and these were approved with additive packages prevalent in the 196Os, notes Dr. George Sadler of the National Center for Food Safety and Technology (NCFST) based at the Illinois Institute of Technology. The NCFST’s consortium of polymer manufacturers, converters and food industry representatives sponsors an irradiation task force that is working towards approval of contemporary additive packages and new polymers. Ciba will be working with the FDA to develop a protocol that will allow the notification clearance of additives used in the irradiation process, reports Ciba’s Naeem Mady.

Synthetic/vegetable derived additives

The trend continues toward use of synthetic or vegetable-oil based rather than animal-fat derived additives, agree industry experts. In Europe, this trend is due to concern of bovine spongioform encephalopathy (BSE). Since many companies have customers globally, the concern has spread to the U.S. as well. Some companies continue to be interested in vegetable-based additives for kosher-certified applications.

Slips and antistats

Slip and antistat additives, which function at the surface of the plastic part, are traditionally migratory. The additives are difficult to predict and control because migration occurs over time and depends on part thickness and polymer crystallinity, explains Dr. Victor Mimeault, Senior Vice President Technical at Ampacet Corporation. Ampacet introduced non-migratory, surface-functional slip and antistat products that fit a need for controllable, predictable performance in premium films. Other advantages of the slip are that it can be used at higher temperatures than conventional slips and has no adverse effect on sealing. The nonmigratory antistat does not interact with adhesives, has no effect on sealing or printing and has high thermal stability. Its antistatic properties last longer than those of conventional migrating antistats and its surface resistivity is similar at 50% and 12% relative humidity. The non-migratory additives are used at much higher levels than traditional additives and so are more expensive. They find use in coextruded structures, such as a film that has slip on the inside but not on the outside, says Dr. Mimeault.

One trend for antistatic additives is the use of longer chain materials, explains Dr. Ashutosh Sharma, technical service and market development manager for polymer additives at Akzo Nobel Polymer Chemicals. Longer chain antistats provide higher temperature processing stability, which is in increasing demand as extruders are pushed to faster rates. A trend for slip additives is to use higher purity slips with reduced shortchain (four to nine carbon) impurities. These higher purity slips have lower organoleptics, or taste and odour components, notes Dr. Sharma.

Croda recently introduced a loworganoleptic erucamide slip product called IncroslipC(r) that has advantages for the bottled water and beer industries. Plastic screw-type bottle closures contain high amounts of slip to enable torque release. Irradiation or sterilization of bottles by UV or ozone can degrade the trace amounts of byproducts inherent in erucamide and produce off-tastes and odours. IncroslipC has improved stability and is less susceptible to degradation than standard torque-release products, notes the company.

Antioxidants

Two new, high performance antioxidants from GE Specialty Chemicals perform well under harsh conditions such as gamma irradiation of food packaging, notes Benjamin Watkins, stabilizer business leader at GE. Ultranox(r) 641 is GE’s improved solid phosphite, and GenoxrM EP is an amine oxide derived from vegetable oils.

Clariant introduced Hostanox 03, a phenolic antioxidant with reduced water extractability that gives it an advantage in liquid food products and in those applications requiring excellent post thermo-oxidative stability at 150°C after 14 days hot boiling water extraction. The antioxidant reportedly does not discolour, as typical phenolics do in either a quinone methide dimerization reaction in the dark that causes pinking or in a gas-staining reaction with prompt oxides of nitrogen that causes yellowing.

Ciba has received positive feedback from companies using its Vitamin E antioxidants for improved organoleptic properties for sensitive applications such as plastic milk and beverage bottles. Ciba(r) Irganox(r) E 201 is a powerful stabilizer that is effective at very low concentrations because it reacts with carbon-centered radicals, says the company.

Colorants

A variety of organic and inorganic colorants are allowed by FDA for indirect food contact; other colorants are exempted from FDA regulation based on migration testing in a specific polymer for a specific application. “Over the past two to three years, we have seen an increase in the number of FDA exemptions, especially for dyes, which are not allowed by FDA,” explains John Wood, technical manager at Teknor Color Company, a subsidiary of Teknor Apex Company. The industry trend towards thinner parts creates a need for a higher colorant loading to maintain color intensity and opacity. This has driven demand for higher pigment levels in ‘super concentrates’ to maintain costeffectiveness. “High-efficiency concentrates can contain pigment loadings of 75% or greater, compared to levels of 20 to 50% for conventional concentrates,” says Mr. Wood.

Antifogs

In fresh-cut produce packaging, antifogs prevent the film from fogging so that the consumer can see the product clearly.

“The use of antifogs in fresh food packaging is on the increase and will continue into the future as new applications as well as new polymer entrants into the fresh food packaging industry continue to evolve,” comments Ciba. Antifogs act as a surfactant, so that moisture given off by produce forms a transparent, continuous film on the package surface rather than forming beads of water, explains Jeff Brandenburg, president of The JSB Group, a food packaging consultancy based in Massachusetts. Antifogs can be impregnated into the film as an additive or applied as a liquid coating. A new trend towards microwaving of fresh-cut produce packages, such as spinach products, has led to challenges of meeting performance requirements and regulatory requirements, which are stricter at elevated temperatures, comments Mr. Brandenburg.

Cryovac Inc., a subsidiary of Sealed Air Corporation, produces films with an anti-fog coating. For example, the Cryovac (r) Microwaveable Vegetable Bag, which won a Flexible Packaging Association award in 2000, has an antifog coating. The coating also aids in improving the shelf life of the vegetables, says the company. The extended shelf life is due in part to the permeability of the package, but also to the “synergistic effect of the antifog coating that reduces moisture, which can encourage the growth of spoilage bacteria,” says Myra Hughes, fresh-cut produce marketing manager for Cryovac.

Antimicrobials

The use of antimicrobials, or biocides, in packaging is 3 a growing trend in the global food packaging industry. In the U.S., many of the antimicrobials in use protect the packaging or the packaging raw materials, although recent interest has been in antimicrobials to protect the packaged food. Antimicrobials that are incorporated into food packaging are regulated by the FDA under the Federal Food, Drug and Cosmetic Act (FFDCA). Under the FFDCA, the FDA ensures that such antimicrobial uses are safe with respect to any potential human dietary intake. Unrelated to federal requirements under the FFDCA, antimicrobial products used in food packaging that have no intended antimicrobial effect on the processed food in the package are subject to EPA registration as pesticides under the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA). Antimicrobials added to food or delivered to food via the packaging are treated as direct food additives and are not subject to FIFRA. In 2000, the EPA issued a Pesticide Registration Notice explaining FIFRA’s Treated Article Exemption, which applies to articles treated with an antimicrobial only to protect the article itself. It clarified that companies cannot make explicit or implicit health benefit claims and must state to customers that the biocide is solely for protection of the article when marketing products qualifying for the Treated Article Exemption. Research at Clemson University has looked at coating food packages with nisin, particularly for hot dog packaging, explains Dr. Kay Cooksey, associate professor of packaging science. Nisin is produced commercially under the trade name Nisaplin(r) by Aplin-Barrett in the U.K., and can be compounded into the packaging polymer or applied as a powder or a coating. It is widely used in Europe but not extensively in the U.S., although it has FDA approval, notes Dr. Cooksey. Silver compounds are also used in Europe and have FDA approval for some applications. Other research is looking at additives that produce the antimicrobial chlorine dioxide under certain relative humidity or UV light conditions. The advantage of these systems is that the antimicrobial could protect any product within the package, not just what comes in contact with a protective coating, notes Dr. Robert Testin, professor of packaging science at Clemson. Chlorine dioxide is also less expensive and effective for a broader range of microorganisms than nisin, adds Dr. Cooksey. The additives are currently being used in a sachet inside the package, but can be compounded into the packaging polymer. Bernard Technologies holds patents on this technology and received GRAS notification from FDA. Current research at Clemson is investigating ways to improve the release of the product into the package.

Freshness Indicators

A major trend in the food industry over the past several years has been the consumer’s desire for freshness in taste and appearance and freshness indicators are an upcoming technology, predicts Dr. Testin. Modified atmosphere packaging controls the flow of carbon dioxide through the food package to extend shelf life, but is dependent on storage conditions in the store or home. Indicators to show when a food has begun to decay are currently being used in bulk packaging, such as the Vistab 8 adhesive labels from Cox Technologies. Current research is focused on making indicators cost-effective for individual packaging, says Dr. Testin. Indicator dyes work by either changing as a function of time and temperature or by reacting with a food degradation product. For example, an indicator in a sensor or in the packaging film could react with an amine given off by fish at the beginning of decay, explains Dr. Testin.

Oxygen scavengers

The use of oxygen absorbers is a relatively new additive trend in food packaging, comments Ciba. Oxygen scavengers are especially important in the trend towards single-serve packages because of the smaller packages’ increased surface volume and exposure to oxygen, says Chevron-Phillips Chemical Company LP Commercial oxygen scavengers include iron oxide powders enclosed in sachets, additives incorporated into the packaging polymer or a polymer layer extruded as part of the package to maintain freshness by absorbing headspace oxygen and oxygen that enters the package.

Ciba’ Shelfplus^TM O₂ oxygen scavenger is a polymer-based additive that can be incorporated directly into the walls of the package. It can be incorporated into either an existing layer within the package or as a distinct scavenging layer.

CP Chemical introduced an oxygen scavenging polymer system consisting of an oxidizable resin, ethylene methyl acrylate cyclohexene methyl acrylate (EMCM) and a masterbatch containing a photoinitiator and a cobalt salt catalyst. Other oxygen scavenging polymers based on nylon, polypropylene, polybutadiene and polyisoprene degrade on oxidation into by-products that can migrate into packaged food and cause off-taste or odour, notes CP Chemical. EMCM does not degrade into compounds that cause off-taste or odour and the photoinitiator allows the inactive polymer to be stored and then activated by UV light during the package filling process, says the company.

Cryovac introduced an improved oxygen scavenging film that reportedly removes oxygen lo-20% faster than before. The Cryovac (r) OS Films ” slow microbial growth and oxidative deterioration of flavours, colour and nutrients,” states the company. A Nestle fresh pasta package using the film recently won an award for technical innovation from the Flexible Packaging Association. The oxygen scavenging process increases the shelf life of refrigerated pasta by more than 50%, notes Nestle.