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For the storage experiments, empty epoxyphenolic coated cans were filled with four foods: soup, minced beef, evaporated milk and carrots, and a food simulant (10% ethanol). The filled cans of each food type or simulant were then sealed and processed using appropriate conditions (30 minutes at 121 C for evaporated milk; 90 minutes at 121 C for other foodstuffs), before storage at three different temperatures: 5 C, 20 C and 40 C. For each of the storage regimes, half of the cans were dented (by impact deformation giving reproducible damage) to establish if this would lead to increased BPA migration. Cans were removed from these stocks at intervals of 1, 3 and 9 months storage at 5 C and 20 C, or 10 days, 1 and 3 months at 40 C. Some initial problems of heterogeneity between samples were overcome by looking at the amount of BPA in food as well as in the can lining.
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To investigate any effects of cooking/heating foods in the can, retail cans of food were purchased and their can linings analysed to demonstrate that the can type contained an epoxy based internal coating. For each canned food type, a dented and an undented can were investigated. To overcome apparent variability in BPA contents of the can coatings, portions of the foodstuff were removed for analysis from the can before cooking/heating, and further portions taken for analysis of BPA after cooking or heating the remainder of the foodstuff. Foods were either cooked-in-the-can according to manufacturers' instructions or the contents heated in the can by immersing the can in boiling water for 15 or 30 minutes depending upon the can size.
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BPA concentration in the food was measured using a GC-MS technique with a limit of detection of 2 parts per billion.
Bisphenol A (BPA) is an important starting substance (monomer) used in the manufacture of epoxy resins for the internal linings of food cans. The Tolerable Daily Intake (TDI) for BPA was reviewed by the Scientific Committee on Food in 2002 and a temporary TDI of 0.01 milligrams/kilogram set.
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In a survey commissioned by the Agency and reported, in April 2001, as Food Surveillance Information Sheet 13/01, low levels of BPA were shown to migrate from some can coatings to foods. It was established then that this did not present a health hazard. However, little is known about how the levels of BPA migrating could be influenced by damage to the can or storage conditions. A further unknown factor is the possible effect on BPA migration of heating the food in the can prior to consumption of the foodstuff. Some foods are intended to be cooked in the can, and in some cases it is possible that consumers will heat up food in the can. In view of the potentially long shelf life of most canned foods, the fact that the consumer may cook products in the can, and the current interest surrounding exposure to BPA from food packaging, it was felt important to obtain information on all of these factors.
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The project aims systematically to investigate the effects of storage time and temperature, and damage to cans after filling, and the effect of cooking-in-the-can, on the levels of BPA migration. The work will be carried out in order to help identify any potential for additional exposure to BPA from cans stored for longer times, damaged cans, or those foods heated/cooked in the can.
<p>Find more about this project and other FSA food safety-related projects at the <a href="http://www.food.gov.uk/science/research/" target="_blank">Food Standards Agency Research webpage</a>.