Home Canning, BPA-Free

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.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.

 

Liked this post? To receive more like it, subscribe to A Gardener’s Table.

Real Lemon versus ReaLemon

Home preservers often wonder why USDA preserving recipes calling for lemon juice specify that the juice should come from a bottle. In most grocery stores the only such product used to be ReaLemon, which is made from concentrate and preserved with sulfites. Today a few competing brands of lemon-juice-from-concentrate are available, with similar assortments of preservatives. To most discerning cooks, ReaLemon and its imitators don’t taste quite real, and to people allergic to sulfites these products may be a health hazard. Bottled fresh lemon juice, with juice from Sicily or Peru, is available at some fancy grocery stores, but it also contains sulfites. Why shouldn’t home preservers use fresh lemons, which are inexpensive and available year-round in every supermarket? Is ReaLemon really better than real lemon?

Extension agents explain that lemons vary in their acidity, and that bottled lemon juice does not. To make sure your jam or your salsa–or, especially, your lemon curd— reaches a safe level of acidity, you should always use the bottled stuff, say the home economists. I decided to find out whether they’re right.

I first researched laws regarding bottled lemon juice. The Code of Federal Regulations (Title 21, volume 2, revised April 1, 2010), includes this FDA rule: Lemon juice prepared from concentrate, like ReaLemon, must have “a titratable acidity content of not less than 4.5 percent, by weight, calculated as anhydrous citrus acid.” Citric acid is the main acid in lemons. Lemons also contain some malic acid, but it usually isn’t measured separately. The ascorbic acid, or vitamin C, for which lemons are justly valued is destroyed by heat and so ignored in discussions of food processing. For our purpose here, we can say simply that lemon juice made from concentrate must have an acid level of at least 4.5 percent, and that the law allows this acid level to vary.

Hmmm. Even if the law allows a variable acid level, a manufacturer would settle on a standard, right? In the opinion of my husband, a chemist, that standard would be 4.5 percent. After all, water is cheap! Why would ReaLemon use more lemons than necessary?

I asked the folks at ReaLemon whether they standardized the acidity of their lemon juice and, if so, what their standard was. Here is their reply: “ReaLemon meets or exceeds the FDA standard of identity for lemon juice, which is 4.5% w/w.” This reinforced my husband’s opinion: ReaLemon had a standard acid level, and it was 4.5 percent.

We decided to test this hypothesis. I bought a bottle of ReaLemon, and we titrated the juice (I’ll explain in another post how to do this). ReaLemon tested at 4.9 percent—the “natural strength” of lemon juice, according to the label. The company rose in our estimation. They were exceeding a minimum standard!

If lemon-juice-from-concentrate is at least 4.5 percent acid, and sometimes 4.9 percent acid, what is the natural range of acidity in lemons? I posed this question to David Karp, a fruit researcher at the University of California, Riverside, who also writes for the Los Angeles Times. David referred me to Walton Sinclair’s Biochemistry and Physiology of the Lemon (University of California, 1984), a four-inch-thick summary of all scientific research on Citrus limon.

According to the research, some lemon varieties are more acidic than others. Lemons of a single variety can vary in acidity depending on the local soil and climate, the rootstock on which the tree is growing, the amount of fertilizer applied, and the season in which the lemons were picked. Lemons and other citrus fruits grown in hotter places, for example, are generally less acidic than those grown in cooler places. Both potassium and nitrogen fertilizers tend to increase acidity levels. New Zealand lemons are less acidic than California lemons, and California lemons are less acidic than Sicilian lemons.

Even a single lemon can show variations in acidity, depending on when you do the testing and from what part of the fruit you take the juice. California lemons increase their acid levels almost 25 percent during curing–that is, in the weeks of storage after harvest. One study found that juice from the stem end of a lemon is slightly more acidic than juice from the blossom end, and another study found that juice from the core area is slightly more acidic than juice from the periphery.

If all these variables make you think the home economists are right, think again. Although lemons vary in acidity, they generally don’t vary much. The least acidic lemon found among all those tested in dozens of studies, an uncured Eureka from California, had an acid level of 4.53 percent. The most acidic uncured Eureka tested at 6.50 percent, and cured Eureka lemons ranged from 5.71 to 7.42 percent. Lisbon lemons from California varied less, from 4.79 to 4.86 percent acid before curing and 5.25 to 5.32 percent afterward.

Florida lemons vary no more in their acidity than California lemons. In one Florida study, samples ranged from 5.16 to 6.41, in another from 5.24 to 5.92.

If you live outside the United States, the lemons in your market may be more or less acidic. In New Zealand lemons averaged only 4.9 percent acid, and in Italy lemons tested as high as 8.1 percent acid. But you won’t find lemons from New Zealand or Italy in Safeway or Albertsons.

Note that I’m not counting Meyer lemons as lemons. A cross between a lemon and an orange, the Meyer is relatively low in acid. Meyer lemons sampled in July averaged 2.4 percent acid in one study; those sampled in February and May averaged 4.1 percent acid.

With all this information before me, I guessed that the juice of a lemon from one of my local grocery stores would test at somewhere around 6.0 percent acid. It would almost certainly be a Eureka or a Lisbon (the fruits of these two varieties are hard to tell apart) or a clonal selection of one or the other. If it were a Eureka, it might be a little more acidic than 6.0 percent; a Lisbon might measure only about 5.0 percent.

So I bought a lemon, and my husband and I titrated the juice. It tested at 6.2 percent acid. Eureka! (Probably.) We drank some of the juice, too, and compared the taste with that of ReaLemon. The natural lemon juice was much less bitter (ReaLemon, like other varieties of bottled lemon juice, contains oil from the peel) and noticeably more sour.

Provided you start with regular lemons rather than Meyers, then, substituting fresh lemon juice for bottled in canning should be entirely safe, although the finished product might end up a little more tart than it would with bottled lemon juice.

Are you adding lemon juice to jam or jelly? This is done not for safety, generally—nearly all fruits are acidic enough for safe canning—but to ensure that the jam or jelly will jell. You can add a little less lemon juice than a recipe specifies if your fruit is quite tart, or a little more if you want a stronger gel.

If you’re canning tomatoes, the acidity of your lemons shouldn’t be a concern. Nearly all tomatoes are acidic enough to can without added acid. If yours are unusually dull in flavor, follow the USDA recommendation: Add 1 tablespoon lemon juice per pint of whole, crushed, or juiced tomatoes. Or, if you like, add more.

Recipes for canned salsa call for quite a lot of lemon juice (or lime juice, or vinegar). If you’re using several fresh lemons, their acidity will average out, and the average will almost certainly be higher than 4.5 percent. By using fresh lemons you may risk making your salsa a little too tart, but you can minimize this risk by using low-acid, paste-type tomatoes, such as Roma, which provide the additional advantage of making salsa thicker.

A particular concern of many home preservers is the safety of fresh lemon juice in canned lemon curd, a tart, buttery custard that’s used as a dessert topping and filling and as a spread for toast, pancakes, waffles, and so on. It’s essential to have a high level of acid in a protein-rich food that’s processed in a boiling-water bath. Home economists say that canned lemon curd is safe only if the lemon juice comes bottled, but remember: American store-bought lemons—the regular kind, not Meyers—are at least as acidic as bottled lemon juice. Besides, you may prefer to use more lemon juice in your curd than called for in the USDA recipe, which, I notice, contains proportionally less lemon juice than does my recipe in The Joy of Jams. You can find the USDA recipe here.

Lemon curd doesn’t need canning, of course. If you put it in a jar in the refrigerator instead, it will keep well for several weeks. You can also freeze lemon curd, and thaw it in the refrigerator for a day before you plan to serve it. If you have a lot of lemons and want to juice them right away, you might freeze the juice so you can make lemon curd as you need it. Lemon juice keeps very well in the freezer.

If you want to give your lemon curd as gifts, though, you may be set on canning it. In this case, be sure to follow the USDA processing instructions. Heat the water to no more than 180 degrees F. before adding the jars, and boil them for 15 minutes, or longer if your altitude is over 1,000 feet.

When you give a friend a jar of your homemade lemon curd or another preserve, you can feel proud that you’ve used the tastiest, freshest ingredients, and confident that your gift won’t prompt an allergic reaction to sulfites.

 

Liked this post? To receive more like it, subscribe to A Gardener’s Table.