Chapter 15
Bisphenol A in Japanese Canned Foods
Downloaded by UNIV OF CINCINNATI on February 18, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2014 | doi: 10.1021/bk-2014-1162.ch015
Yoko Kawamura* Division of Food Additives, National Institute of Health Sciences, Tokyo 158-8501, Japan *E-mail:
[email protected].
Bisphenol A (BPA), a suspected endocrine disrupter, is used mainly as a monomer in the production of polycarbonate and epoxy resins. Metal cans for food are usually coated with BPAbased epoxy resins. Therefore, the residual BPA in the can coatings has a possibility to migrate into canned food when the canned food is heated over 105°C during cooking and/or sterilization. We surveyed BPA Levels in 100 domestic, and 60 imported canned foods purchased in Japan. In the domestic canned foods, the highest BPA level was 30 ng/g in hashed beef stew, and the average was 3.7 ng/g. On the contrary, the imported canned foods contained much higher BPA levels. The maximum BPA level was found 390 ng/g in demiglace sauce, followed by 340 ng/g in white sauce, 320 ng/g in gratin sauce and blue crab. The average was 57 ng/g, which was 15 times higher than that found in the domestic cans. The BPA levels in the domestic canned foods showed a significant reduction in comparing to the levels found in the imported cans or reported in other surveys. This drastic reduction is likely due to the use of “BPA reduced cans” which Japanese can manufacturers have developed in the past decade.
© 2014 American Chemical Society In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
Introduction
Downloaded by UNIV OF CINCINNATI on February 18, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2014 | doi: 10.1021/bk-2014-1162.ch015
Bisphenol A (2,2-bis(4-hydroxyphenyl) propane, BPA) is a suspected endocrine disrupter producing estrogenic effects (1). Its chemical structure is shown in Figure 1. It is mainly used as a monomer in the production of polycarbonate (PC) and epoxy resins. Because of its use, food contact articles made from PC or epoxy resins usually contain trace levels of free BPA, which has a possibility to migrate into foods.
Figure 1. Chemical structure of bisphenol A.
PC products contain BPA as an unreacted monomer and also a degradation product of PC. The BPA residues were found to be 5-80 μg/g in dishes and 18-37 μg/g in baby bottles in Japan, though their migration levels were mainly below limit of detection (2). However, Japanese consumers refused to buy PC tableware and baby bottles, then the Japanese manufacturers stopped their production in about year 2000. Therefore, the market share for PC baby bottles was significantly reduced to less than 1% on the Japanese market, and polyphenylsulfone and polyethersulfone became the substitutes for PC. The Japanese government has not prohibited PC baby bottles yet, but Canada, the EU, China and several other countries have. Epoxy resin is a thermosetting copolymer formed from the reaction of an epoxide resin with a polyamide hardener. The most common epoxy resin is the diglycidylether of BPA produced from epichlorhydrin and BPA. Epoxy has a wide range of applications including paints, coating and adhesives. For food contact purposes, it is used as a coating of tablewares and metal cans, and as an adhesive for laminate films. Most of epoxy resins contain residual BPA as an unreacted monomer. Metal cans for food contact are commonly coated on the surface by epoxy resin to protect both cans and foods, because cans can be eroded by foods, and foods then are contaminated by the released metal ion. Epoxy resin is very stable under its glass transition temperature (ca. 105°C), but above 105°C its physical property changed and begins to release free BPA to moisture contacted with it. Therefore, when food is packed in a can and heated during cooking and/or sterilization over 105°C, BPA will readily migrate into the food from the can coatings. The migration levels in canned foods are extremely higher than that from polycarbonate products. The main source of human exposure to BPA is from the diet, especially the canned foods (3, 4). 156 In Food Additives and Packaging; Komolprasert, V., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2014.
157
Downloaded by UNIV OF CINCINNATI on February 18, 2015 | http://pubs.acs.org Publication Date (Web): July 22, 2014 | doi: 10.1021/bk-2014-1162.ch015
Table I. Frequency, Maximum and Average of BPA Levels in Canned Foods Reported in Literatures Japan (Ca. 2000)(3-7) Food group
U.K. (2002)(8)
New Zealand (2005)(9)
Canada (2009)(10)
U.S.A. (2011)(12)
Belgium (2010)(11)
Freq. (%)
Max. (ng/g)
Ave. (ng/g)
Freq. (%)
Max. (ng/ g)
Ave. (ng/g)
Freq. (%)
Max. (ng/ g)
Ave. (ng/g)
Freq. (%)
Max. (ng/ g)
Ave. (ng/g)
Freq. (%)
Max. (ng/g)
Ave. (ng/g)
Freq. (%)
Max. (ng/ g)
Ave. (ng/g)
Fish
67
97
36
90
44
21
50
109
28
100
534
137
100
169
75
100
22
12
Meat
91
602
139
100
422
108
33
98
28
−
−
−
100
27
27
−
−
− 88
Vegetable
78
95
32
100
48
27
65
24
13
100
92
20
100
116
42
92
730a
Fruit
11
7
1
100
41
29
0
< 10
0
−
−
−
100
20
12
64
19
5 72
Other food
67
86
33
53
41
12
25
21
8
94
189
68
100
73
35
100
790b
Coffee, tea
58
213
26
−
−
−
−
−
−
−
−
−
100
1
0.7
−
−
−
Other drink
0
