Cause of bisphenol A migration from cans for drinks and assessment of improved cans

In the previous investigation, we found that some cans for coffee and black tea drinks released large amounts of bisphenol A (BPA) into their contents. Equivalent cans were obtained and the cause of BPA migration was investigated. Equivalent cans A, B and D contained high levels of BPA in the side seam, in the bottom, and in the bottom and the side seam, respectively, while can C contained some level of BPA in the body, which has a large area, therefore, all of them contained high amounts of BPA in their coatings. In the migration test, there was no BPA migration from the cans into water at 60 and 95 degreesC for 30 min, into 20% ethanol at 60 degreesC for 30 min, or into n-heptane at 25 degreesC for 60 min. However, at 120 degreesC for 30 min, equivalent cans released 35 similar to 124 ng/ mt BPA into the water. The total migration was similar to the total residues of BPA in the can coating and was close to the total amount of BPA in the drinks. Thus, BPA migration from the can coating requires heating to more than 105 degreesC, which is the glass transition temperature of the epoxy resin. Improved cans which contained less than 1/10 as much BPA as the equivalent cans showed very low migration levels, ie., 3 similar to6 ng/mL.