May 2015 Issue of Wines & Vines
 
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HACCP Considerations

Plastic polymers in the wine industry

 
by Brent Trela and Cassandra Plank
 
 

Plastics are ubiquitously used in the food and beverage industry and are an alternative to traditional packaging materials for wine. Ingredients used in manufacturing plastics may include additives such as heavy metals that act as catalysts in the plastic polymerization process and plasticizers used to modify and improve the applicability and durability of plastics.

Common plastic ingredients include bisphenols and phthalates. Phthalates are typically used to soften plastics and are used in many products from polyvinyl chloride (PVC), lubricants, emulsifying agents, binders and gelling agents, to enteric coatings on pharmaceutical tablets.

Bisphenols, such as bisphenol A (BPA), are used to harden plastics and include polycarbonate plastics and epoxy coatings. Many additives intercalate within plastic polymers and may leach into materials in contact with the plastic.

As plasticizers, phthalates do not chemically bind to the plastics in which they are mixed, and plastic-bisphenol polymers can be hydrolyzed or may be incompletely polymerized, therefore, both types of chemicals can leach from the products into the environment.

Contamination of wine with plastic additives can occur during processing, storage and transport. GC-MS and LC-MS are among the most common analytical tools to analyze for bisphenols and plasticizers.

practical winery vineyard
 

Plastic ingredients
Inorganic or organic substances may be added to plastics to enhance the processing and properties of the plastics (e.g. stabilizers, plasticizers, biocides, flame retardants, pigments and others).11 One of the largest and most controversial groups of additives is plasticizers.

Epoxies are used in applications such as lining metal cans and concrete wine tanks.

Plasticizers are a class of organic compounds added to plastics to improve flexibility and durability, without which plastic may be too rigid and brittle.25,45 PVC polymers use almost 90% of plasticizers produced worldwide.5

The most common types of plasticizers are the phthalate esters (Table I). PVC is predominantly plasticized with diethylhexyl phthalate (DEHP). However, due to health concerns and governmental regulatory changes,14 DEHP use is declining and being replaced with non-phthalate plasticizers such as polyester.47

The bisphenols, of which BPA is the most widely used, are used in the production of epoxy resins and polycarbonates. Epoxies are used in applications such as lining metal cans and concrete wine tanks.

Polycarbonate plastics are used in food and beverage storage containers. BPA may also be used as an antioxidant in PVC production.20

Health issues
Many plastics have additives or unreacted feedstock of the component plastics that may have biological consequences. BPA and phthalates are used in food and beverage packaging materials, including wine packaging, and have been found to leach into foodstuffs over time.16,45 Exposures to phthalates and BPA can cause endocrine disruption and estrogenic effects that have been linked to human health problems.19,25

BPA has been suggested to alter human development and cause breast and prostate cancers.2 It leaches from plastic bottles and food packaging, especially when heated or brought into contact with acidic food.16 This prompted many companies, such as those that manufacture baby bottles, to discontinue the use of BPA in their products.31

The European Union and the United States Food and Drug Administration prohibited BPA use in baby bottles in 2011 and 2012, respectively.29,33 California intends to list BPA on its Prop. 65 list, which lists chemicals known to the state to cause cancer or reproductive toxicity.30 While many manufacturers have switched from using BPA and claim to be “BPA-free,” they may instead be using other bisphenols that also test positive for estrogenic activity.27

World production of phthalates is estimated to be several million tons per year.34,52 Unlike some plasticizers, phthalates are not chemically bound to plastic products and therefore can leach into foodstuffs.57 The U.S. Environmental Protection Agency (EPA) limits phthalates according to the Phthalates Action Plan, because the amount of leaching into water sources can be toxic to terrestrial and aquatic animals.35,50

The most common phthalate is diethylhexyl phthalate (DEHP, CAS 117-81-7), which is regulated under the EPA’s Safe Drinking Water Act at a maximum contamination limit of 0.006 mg/L.49 DEHP is classified by the EPA as a class B2 probable human carcinogen and acts as an endocrine disruptor in the body.57

Polyethylene is generally considered to be plasticizer-free. Polyethylene polymers provide ranges of flexibility suitable for various uses and therefore usually do not require plasticizers to alter their flexibility, and bisphenols are not required in their manufacture.

Nevertheless, a study that investigated children’s exposure to DEHP and di-n-butylphthalate (DBP) from school meals found that the estimated daily intake for these chemicals was variable but could reach levels near the tolerable daily intake levels set by the European Food Safety Authority.10

Polyethylene terephthalate (PET), also known as Dacron, or polyester, is used for bottled water and fruit juices and has been shown to be a source of phthalates as well as antimony, the catalyst used in PET production, especially if stored at elevated temperatures.

In some cases, concentrations of phthalates and antimony in PET-bottled water have been reported to exceed regulated limits.23,36,46 Recycled PET could be a source of other chemical compounds that may have health implications.

Plastics and plastic additives in wine
Plasticizer contamination is common through storage in plastic containers and possible pollution of raw materials. Recent incidents with plasticizer contamination include a food safety emergency in Taiwan in May 2011.24,55

Plasticizers have also been found in Chinese baijiu, a white spirit usually distilled from sorghum or other grains. The Jiungui liquor company found that samples of the product contained 1.04 mg/kg of DBP, which is more than three times higher than the 0.3 mg/kg standard set by the Ministry of Health in June 2011.9,58

Large-scale tests of China’s liquor have shown that almost all alcohol products contain an average level of 0.537 mg/kg of plasticizers.59 DBP and diisobutyl phthalate were found in more than 94% of food samples, but they were significantly higher in wine and beer compared to other beverages.22 These chemicals may come from pneumatic press and pump materials, pump lines, storage and transportation vessels and/or added flavorings.

Just as in liquor manufacturing, various stages in winemaking may involve plastic products containing leachable plasticizers and other additives that are potentially extractable if the wine comes in contact with them. In March 2013, three brands of French Cognac were prohibited from entering China’s market because they reportedly contained excessive levels of plasticizers.18

Plastics are used in the manufacture, transport and storage of wine (Table II). It has been estimated that synthetic closures have taken 19% of the world’s closure market, with metal screwcaps making up 11% of the market of approximately 20 billion wine bottles per year.43

Large-scale tests of China’s liquor have shown that almost all alcohol products contain an average level of 0.537 mg/kg of plasticizers.

The use of artificial closures, screwcap plastic liners and other plastic closures or plastic containers such as bag-in-box, may expose wine to plastic leachates that can alter organoleptic properties in the wine as they do with other foods and beverages.37,53

A wide range of plasticizers have been used in plastic closures compared to other sources of plasticizers in the winemaking process.4,39 Saranex used in both screwcap liners and synthetic closures is a barrier film consisting of layers of Saran resin (polyvinylidene chloride, PVDC) and thermoplastic polymer resins.12

Plasticizers that have been found in PVC-based films include DEHA and phthalates such as DBP and DEHP.21 Low-density polyethylene (LDPE) is used as a replacement for PVC in Saran,38 however it provides a poor oxygen barrier and can scalp flavors from foods.42

Plastic packaging may scalp the volatile flavors from wine, or the wine may absorb undesirable aromas from the plastic.32 Packaging materials may also contain BPA, such as plastic stoppers used to seal partially consumed bottles of wine and the lining of concrete fermentors, which are commonly coated with epoxy that may contain PVC.37,40,44

Due to the widespread environmental contamination, use and presence of plasticizers and bisphenols, there are a variety of sources of potential contamination in the winemaking process. Besides packaging materials, pumps, tubing, transport containers, pneumatic press material and additives can all contain or be contaminated with plasticizers or bisphenols.4,6,39

Options to reduce toxicity due to plasticizer leachate include the use of alternative plasticizers such as the replacement of petroleum-based plasticizers with those derived from natural compounds.

Biopolymers derived from polysaccharides, proteins, lipids and microbes are potential sources for natural plasticizers. Biopolymers have less toxicity, leachability and are biodegradable, however, they tend to have reduced mechanical properties and performance.52 Biopolymers currently only share 5% to 10% of the market and cost more than their non-biopolymer counterparts.

Many petroleum-based plastics contain leachable additives that have the potential for health effects. Nevertheless, many food contact-approved plastic resins, such as specific formulations of polyethylene, currently offer useful functional properties and do not contain additives or other substances that cause cancer, birth defects or reproductive harm at levels that would require a warning under California Prop. 65.13

Examples of polyethylene products available to the wine industry include wine bottle closures and wine tanks. Nevertheless, even polyethylene products can contain bioactive ingredients added for various purposes (UV stabilization), but not necessarily in all cases.

While manufacturers may state that their products contain no PVC and phthalates are not added during the production process, the plastics used may contain additives that are not bisphenols or phthalates.

It may be relevant to certain wine producers and their customers that some plastics, such as polyethylene, may contain additives synthesized from animal extracts such as fatty acids produced by the hydrolysis of animal fats (tallow), and there may be corresponding declarations of compliance or noncompliance with various religious dietary laws such as kosher laws.13

Concerned users of plastic products may want to contact manufacturers for details about the identity and/or purity of the plastic resin(s) used, notwithstanding nondisclosure of proprietary information.

Currently there is no simple way of identifying the purity of these products except by the manufacturer’s resin code and supporting regulatory data sheet, or independent lab tests. Even independent lab testing can yield compromised results due to the use of plastic products in laboratory systems and their potential to contribute leachates.26

Naturally, wine producers could also simply continue to employ traditional materials (wood, stainless steel, glass and cork) for production and packaging, which largely avoid potential sources of petroleum or animal-based chemicals.

Analytical methods and results
Bisphenols and phthalates are mostly found at trace levels (nanograms per milliliter or less), therefore analytical quantification in both solids and in liquid samples start with liquid–liquid extraction, solid-phase extraction, or solid-phase micro-extraction to concentrate the analytes prior to chromatographic analysis. Phthalate analysis is based mainly on GC-FID, GC-MS, GC/IT-MS, LC-MS, while HPLC and fluorescence detection have been used for bisphenols.3,7

DBP, BBP, and DOP have been found in wines, including DEHP at levels exceeding the EPA limit (6 g/L) for DEHP in water, particularly in a wine with synthetic or agglomerated cork stoppers.7,39 Total phthalates in the wines analyzed ranged between 2.7 and 15 µg/L.7 BPA also has been found in wine stoppers and wines stored in steel, wood and plastic vats, glass bottles and Tetra Paks (mean concentration 0.58 ng/mL).3

Bisphenols and phthalates are present in disposable laboratory plasticware such as pipette tips. Other additives such as oleamide and biocides have been found to leach from laboratory polypropylene disposable plasticware that affected protein function in biological research.26 Therefore plastic contamination presents significant data compromise challenges.

Similar to materials used in winemaking, laboratories can seek manufacturers that disclose information on the additives content as well as leachable reaction components used in the manufacture of their plastics. Regardless, researchers may still need to confirm the absence of effects or account for them in their assay methods and results.

Conclusions
Plastics and their additives, including those that cause health concerns, are ubiquitous in the environment and in food and beverage processing and packaging materials. There are numerous opportunities for wine to leach additives from plastics. Reported work has shown some wines contain certain plasticizers at concentrations that are prohibitory in some markets.

Wine producers should be aware of the possible sources of plastic additives, the potential for these to accumulate in their products and health concerns and regulations regarding their presence in the “most healthful and hygienic of beverages,” (Louis Pasteur).

Improved transparency from manufacturers regarding potential leachates in their products would be helpful as well as increased availability and affordability of alternatives such as bio-based or additive-free plastics.

Other issues to be aware of include plastic permeability to gases such as oxygen, as well as permeability and adsorption/flavor scalping potential of low molecular weight flavor and aroma compounds that could impact the quality of the product that comes into contact with plastics.

Some plastic ingredients may also be objectionable to various market groups such as those that follow certain religious or personal guidelines. HACCP approaches that identify and prevent potential hazards (including marketing hazards) from occurring may lead to safer products and better customer trust, marketability and ultimately sales of a winery’s product.
 

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