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Bisphenol A - A problem for consumers of canned beer? - Potential risks and analysis of debatable plastics used in canned beer coatings
L.-A. Garbe, K. Neumann, N. Rettberg

The precise determination of Bisphenol A (BPA) amounts in complex matrix like beer is presented. A practical, rapid and reliable sample preparation procedure for BPA determination is shown. The application of stable isotope dilution assay (SIDA) utilizing labmade deuterated BPA standards made it possible to obtain accurate analytical data. BPA concentrations in seven randomly chosen canned beers ranged from 1 g BPA/L to 6.5 g BPA/L. Compared to other canned foodstuff these amounts are low and presumably safe.2,2-Bis-(4-hydroxyphenyl)-propane, commonly known as Bisphenol A or simply BPA, is a chemical agent existent in many products of everyday life. BPA is synthesized by coupling two equivalents phenol with acetone under hydrochloric acid catalysis. It is mainly employed as starting substance for the production of robust polycarbonate plastics (PC) and epoxy-phenolic resins, but also used in polyvinyl chloride (PVC). Industrial BPA production in EU countries accumulates to about one million tons per year [1].PC plastics are prevalently utilized for the production of CDs, DVDs, mobile phones or computer cases due to their high resistance, ductility, and hardness. But, they are frequently used in food and beverage packaging, plastic table ware, or baby drinking bottles. Epoxy resins are part of paints, floor covers, adhesives as well as (water-)pipe linings. In food industry, reaction products of BPA with epichlorhydrin, forming Bisphenol A diglycidiyl ether (BADGE), are used. Those are predominantly introduced as inner can coatings in order to circumvent contact between can content and metal surface [2]. The presence of unpolymerized BPA is encountered the main problem when BPA polymers are used in immediate contact to food. Monomers originate from uncompleted polymerization, mechanical decomposition or cleavage by chemical hydrolysis. Those BPA monomers are reported to migrate from coating to packed product, being a source of contamination for foodstuff [3, 4, 5]. Consumption of products from BPA containing packages is considered the main source of consumers BPA exposure. Several research groups published BPA levels for various canned foods and beverages, however, data for BPA in beer is rare. In the literature analytical approaches differ considerably. They are mainly based on liquid chromatography coupled with mass spectrometry (LC-MS), a costly and uncommon technique in brewery quality assurance labs. A selection of BPA concentrations is illustrated in Table 1.There are considerable differences in BPA concentrations between canned dairy products, fruits, vegetables, and soft drinks. Those are liable to characteristics of packed foodstuff (e.g. pH), different can types with varying thickness of resin coating as well as processing techniques. Especially the intensity of heat treatment is proposed to be highly significant. Whereas beverages usually are only subject to pasteurization (≥ 65 C) canned food is exposed to higher temperatures (≥ 100 C) [8].The hygienic outcomes of oral BPA exposure today are still discussed very controversially. The major problem to evaluate BPA risks in humans is the lack of reliable data and long term studies. Animal tests show inconsistent results and do not adequately reflect the situation for humans. Especially, the action of BPA as endocrine disruptor does not allow direct comparison of animal testing data to humans. The nature of its estrogenic activity was already discovered in 1936 [9]. Later investigations, mainly applying rodents and aquatic organisms, showed BPA binds to and activates estrogenic receptors with multiple follow-ups for tested species [10]. In addition to the hormonal impact, BPA is reported as substrate of several metabolic reactions. It is converted into reactive intermediates and may also cause oxidative stress due to further degradation [11, 12, 13]. In contrast to multitude studies using various animal species, only limited data is available for the effects of BPA on humans. Nevertheless, a recently published study conducted on humans showed a correlation of high urinary BPA concentration and an increased risk for type II diabetes and cardiovascular disease [14]. Even critics note that in animal testing pure BPA is used and real uptake therefore is not correctly simulated, its impact on living organism cannot be denied. Renowned institutions engaged on this topic and guidelines concerning BPA exposure were established. The European Food Safety Authority (EFSA) proposed maximum amounts for BPA intake. At this the full Tolerable Daily Intake (TDI) was set to 50 g BPA/kg bodyweight (bw), derived by applying a 100-fold uncertainty factor to the overall No-Observed-Adverse-Effect Level (NOAEL) of 5 mg BPA/kg bw/day. The EFSA also estimated the exposure to BPA by consumption of commercial foods and beverages to be 1.2 g/kg bw/day. This calculation was based on the assumption a 60 kg adult consumes 1 kg of canned food (50 g BPA/kg) and 2 liters of canned beverages (10 g BPA/kg) per day [15]. In general, the EU enacted a legal ordinance obligating producers and importers of BPA to minimize risks for consumers and environment (REACH) [16]. Considering this, BPA limits are obsolete.

Descriptors: Bisphenol A, stable isotope dilution assay, GC-MS, canned beer

BrewingScience - Monatsschrift fr Brauwissenschaft, 63 (September/October 2010), pp. 122-127