About a year and a half ago, home canners began to learn that the flat metal lids they use to seal their jars, like the metal cans that so much store-bought food comes in, were lined with a plastic coating containing bisphenol A (BPA), a chemical of questionable safety. Since then we’ve learned to limit our exposure to this endocrine disrupter by switching from polycarbonate to stainless-steel water bottles for grownups and from hard to soft plastic milk bottles for babies, and eleven U.S. states and even China have joined Europe and Canada in banning BPA from baby bottles. Those of us beyond babyhood, however, tend to take in BPA mainly through canned food. The linings of most cans haven’t changed.1 Nor have the linings of jar lids, for commercial use or for home canning.
Scientists and governments disagree about the magnitude of this problem, and even whether it’s a problem at all. Canada identifies BPA as a toxin; the European Food Safety Authority (EFSA) believes BPA safe to use in can and lid linings; and the U.S. Food and Drug Administration hopes that industry will find alternatives to BPA without governmental intervention.2 Because studies of the dangers of BPA have produced conflicting results, in November 2010 the United Nations Food and Agriculture Organization (FAO) and the World Health Organization (WHO) held a joint meeting of international experts to review the data on the health risks of BPA. In 2011 the background papers presented at that meeting were edited and posted to the WHO website along with a summary report. The conclusions were that BPA probably doesn’t cause cancer, induce genetic mutations, or, generally, accumulate in the body, but that it may possibly have harmful effects on metabolism, children’s (especially girls’) behavior, and sexual development and reproduction. More studies are needed, the scientists said.
And more studies are under way. In the meantime, many home canners wonder why Ball, Kerr, and their Canadian counterpart, Bernardin, don’t play it safe by changing the coatings of their jar lids immediately. One reason is that these three formerly independent companies are all brands now belonging to Jarden Corporation, which also happens to own FoodSaver, Crock-Pot, Mr. Coffee, Oster, Rival, Seal-a-Meal, and Sunbeam, to name a few of the businesses this conglomerate has devoured. Jarden clearly has its corporate hands full, and no true competitors to worry about. Besides, the BPA-containing epoxy resin coatings, made by corporations such as PPG and Valspar, have for decades done an excellent job of keeping metal from leaching into canned food. Like their fellows in food processing, the folks at Jarden may feel that BPA-containing coatings are still their best choice (see Update, below).
I honestly haven’t fretted about BPA in my jar lids. Food stored in an upright mason jar, after all, needs never touch the lid. Even during processing, jellies and thick jams tend to maintain most of their headspace.
But other home-canned products, such as whole or halved tomatoes, do boil up and touch the lid while the jar is processed in a boiling-water bath or pressure canner. Is it possible to minimize the migration of BPA into home-canned food during processing? No one has performed experiments to find out, but studies on tinned foods offer some hints. According to one of the FAO/WHO reports, more BPA migrates from can linings into food when the food is processed at pressure-canner temperatures than when it’s processed at a lower temperature for a suitably longer period. Processing jars of tomatoes in a boiling-water bath, therefore, may result in less BPA contamination than pressure-canning them. Low-temperature pasteurization, recommended by the USDA for keeping cucumber pickles firm, results in even less BPA contamination in tinned foods than does processing the foods in boiling water. In the case of home canning, using the low-temperature method might result in no contamination, since the liquid in the jar would never boil. Salt tends to increase the migration of BPA into tinned food, according to the report, so unacifidified vegetables such as beets and beans, which you must pressure-can to prevent botulism, might take up less BPA if you left out salt. Oil has the same effect as salt, the report says, so you might prefer to can cooked tuna with water rather than oil.
Acids also increase migration of BPA. Most of this migration happens during processing, but some can occur during storage if the food is in contact with the BPA-containing coating. The coating can’t touch the food as long as the jar stays upright, but some home canners who send their products to friends and relatives worry that even jellies and well-gelled jams may end up tainted by BPA if the parcel is flipped during shipment.
This fear is legitimate. In 2010, Popular Mechanics sent boxes loaded with movement and impact sensors around the country via the U.S. Postal Service (USPS), the United Parcel Service, and Federal Express. The packages got turned upside-down repeatedly during every trip with each company. (Although the USPS dropped the packages the least, it flipped them the most—on average, twelve and a half times per trip!) The package labeled “FRAGILE” and “THIS SIDE UP,” in fact, got flipped the most.
Alternatives to Ball and Kerr
Some home canners have tried to avoid these concerns by hunting down BPA-free mason-jar lids, and several have asked for my help in searching out and testing them. One reader of this blog recommended Leifheit lids, from Germany. These lids are both BPA-free and “bulletproof,” she told me. Before I ordered some, though, I wanted to confirm that they were BPA-free. This should have been easy; Leifheit has a U.S. division with an excellent website. But my emails and phone calls to the company were never returned, and others inquiring about BPA have reported the same experience. One blogger got through to a representative who admitted that the Leifheit lid linings have “negligible traces of BPA.” Perhaps as many traces as Jarden’s lids have, albeit at a much higher price? Nobody seems to know.
One European mason-jar manufacturer makes truly BPA-free metal lids, according to Cathleen O’Keefe of the Massachusetts chapter of the Northeast Organic Farming Association (NOFA). Bormiolo Rocco, an Italian producer of fine glass, sells these mason jars and one-piece caps under the name Quattro Stagioni. Cathleen, who places bulk orders on behalf of NOFA members and anyone else who wants the caps, sold me some in both regular and wide-mouth sizes ($.80 and $1.05, respectively, for a packet of two, plus a little for shipping; Ball lids, when sold with screw bands, cost almost as much). The Quattro Stagioni caps are easy to use: You just rinse them in hot water, fill the jars as usual, and screw on the caps. If I’m translating the Italian instructions correctly, you’re supposed to leave the jars in the kettle of hot water until they have cooled, but I take them out as soon as the boiling period is up, in accordance with USDA recommendations. You can tell the jar is sealed in the same way you can with a Ball or Kerr lid: The vacuum pulls the center of the lid down firm. Nicest of all, you can open the lid by unscrewing it rather than prying it off. Quattro Stagioni caps are not intended for pressure canning.
An American-made, BPA-free alternative to Ball and Kerr lids is a product called Tattler. The Tattler lid is made of solid plastic, a substance called acetal copolymer. This plastic contains no BPA, and it’s approved by the USDA and FDA for contact with food, including meat, provided the food doesn’t contain 15 percent or more alcohol. The plastic lids are guaranteed to last a lifetime, and the company says that in their thirty-five years or so in production no one has ever asked for a replacement. The lids are especially recommended for use with acid food, since acid doesn’t degrade them as it does metal. The lids can be used in pressure canners as well as boiling-water canners.
To make a Tattler lid stick you need a rubber ring, which you place on the jar rim under the plastic lid, and a standard metal band to screw over the plastic lid. The rubber ring is reusable several times, until it becomes stretched, cracked, or cut. The company recommends reversing each ring with each use to prolong its usefulness. You can buy the rubber rings with the lids or separately; the metal screw bands you must get elsewhere.
The recommended procedure for using Tattler lids and rubbers is a little different from that recommended for Ball and Kerr two-piece caps. After scalding the Tattler lid and ring and placing them on the jar top, you screw on the metal band all the way and then turn it back ¼ inch; this allows the jar to vent during processing. After processing, you tighten the metal band as soon as you take the jar out of the canner (use two heavy towels or potholders to avoid burning yourself). When the jar has cooled, remove the metal band. You know the jar is sealed if the lid stays on. To remove the lid, gently insert a table knife between the rubber and the jar.
An Extension food safety specialist at the University of Georgia, Elizabeth Andress recommends allowing 1 inch headspace when canning with Tattler lids, but I can’t imagine why. I suspect this would lead to oxidation—that is, darkening of the food at the top of the jar. When I’ve used Tattler lids, I’ve stuck with the standard headspace measures of ¼ inch for jams and jellies and ½ inch for pickles.
Tattler lids and rings are probably too expensive ($20.95 for three dozen narrow-mouth lids and rings and $23.95 for a wide-mouth set, from the company website) if you are selling or giving away your preserved foods and aren’t sure the recipients will return everything—jar, lid, ring, and band–undamaged. But the lids and rings are very nice for home use, especially with ungelled acid foods such as pickles, relishes, and tomatoes. And Tattler products may be affordable if you can buy them from a local store instead of having to pay for shipping.
Maybe you’re nervous about putting any plastic in contact with your food. Another option is glass—glass jars with glass tops. I’ve long kept some of the German-made Weck jars, which are now widely available at U.S. cookware stores as well as via the Web. These jars come with rubber rings much like the Tattler rings, and stainless-steel metal clamps that hold down the glass lids during processing. The rings shouldn’t be reused, according to the manufacturer, but you may find that like Tattler rings they last well through multiple uses. You know a ring is good when you take the clamps off the cooled jar and the glass lid stays on. For storing opened jars in the refrigerator, Weck sells plastic caps to fit.
When the rubber rings for your Weck jars have worn out, of course, you must find new ones, and until recently this was difficult to do in theUnited States; my Weck jars sat unused for years for this reason. Now, however, the rings are available inexpensively at Weck’s U.S. website.
Some Weck jars come in whimsical shapes; I have “deco” liter jars that are nearly round. USDA processing times are based on jars shaped more or less like Ball and Kerr jars. If this concerns you, either stick with the more standard shapes or increase your processing times a bit.
The only disadvantage I find with Weck jars, besides the prices (for example, six half-liter cylindrical jars cost $18.25, plus shipping, on the Weck website), is the minor difficulty of getting the metal clamps on. I often chip the lids when doing this, though the slight chipping doesn’t damage their integrity.
Should the health risks of BPA induce you to try one or more of these alternative canning products? Perhaps so, if you’re worried, especially if you’re feeding your home-canned goods to young children or shipping them around the country. But first you might try more effective ways of reducing your BPA exposure. Besides shunning polycarbonate bottles, avoid eating foods from metal cans, particularly meats, soups, and vegetables, unless the cans are labeled as BPA-free. Don’t heat food in plastic containers, and wash your hands after handling thermal paper (slick cash-register receipts, for example).
As long as you’re using conventional jar lids, you may be able to reduce your exposure to BPA by leaving the salt out of pressure-canned foods, processing tomatoes in a boiling-water bath, and using low-temperature pasteurization for pickles. Most important, store your jars upright.
Update, May 24, 2013: According to Jarden Home Brands, Ball and Kerr lids produced since last fall have no BPA. Starting this summer, boxes of the lids will be labeled “BPA-free.” Until then, you can find out whether lids in your cupboard or on the store shelf have BPA or not by checking this article at Diary of a Tomato.
1. For a list of exceptions, see this 2010 article by A. K. Streeter.
2. The EFSA and the U.S. Environmental Protection Agency agree that 50 micrograms per kilo of body weight is a tolerable daily intake of BPA. Urine tests have indicated that the average American takes in one-thousandth of this amount. As reported in this 2009 article from Consumer Reports, however, some scientists believe that the 50-microgram limit is much too high.