July 9, 2014

Canning concerns

Sugar and safety: Those are the two big concerns of home cooks when it comes to canning.

Sugar and safety: Those are the two big concerns of home cooks when it comes to canning.

When people even think about making their own jams or pickles, they experience what I call “recipe shock” about the amount of sugar required. (For example, a traditional strawberry jam recipe calls for 5 cups of mashed fruit and 7 cups of sugar.) Many people these days want to limit sugar, either because they are diabetic or for weight control.

When it comes to food safety, canning scares many people because of one threat: botulism. They are too afraid to even try canning their own food for fear of making their loved ones sick. If you understand the science behind safe canning practices, you will know how to eliminate that risk and will can without fear.

I heard these concerns again and again these past several months at events for my first cookbook, “Pickles & Preserves: A Savor the South Cookbook.” With summer fruit season in full swing, here are answers to your most common canning questions with an assist from fellow canning cookbook authors, food scientists and home economists.


Why do recipes for jam, jelly and preserves call for so much sugar?

Sugar does more than provide flavor. It plays a key role in getting the jam to set as well as preserving color and texture and extending shelf life.

“It’s important to recognize that jams and jelly are candy. You are essentially candying the fruit to preserve it,” explained Sherri Brooks Vinton (, author of the best-selling “Put ‘em Up” canning books and the recently released “Put ‘em Up Preserving Answer Book: 399 Solutions to Your Questions.”

Without the correct amount of sugar, Vinton explains, the jam may not set, won’t have that bright, glossy color and ideal texture or last as long once opened.

Can I make jams or preserves with less sugar or no sugar?

Yes. There are low-methoxyl pectins on the market that allow you to use less sugar, Splenda and other sweeteners. Low-methoxyl pectins rely on calcium, rather than sugar, to get jams and preserves to set.

Look for low-sugar, no-sugar pectins by Ball or Sure-Jell, which can be used to make jam with lower quantities of sugar, Splenda or honey.

Vinton and Marisa McClellan, author of the popular Food In Jars blog ( and two preserving books, recommend a product called Pomona’s Universal Pectin (, a commercial pectin packaged for home use. Available online and at Williams-Sonoma and Whole Foods stores, Pomona’s comes with two packets: one of pectin and another of calcium that is mixed with water before it is added to the fruit. Because the calcium helps the jam set, recipes using Pomona’s can use less sugar.

Vinton has two books with recipes that call for Pomona’s: “Put ‘em Up” and “Put ‘em Up Fruit.” In addition, Pomona’s makers recently published a cookbook, “Preserving With Pomona’s Pectin,” by Allison Carroll Duffy.

Can I make sweet pickles with less sugar?

Yes. But using less sugar or a sugar substitute will produce a softer pickle, Vinton notes. Reducing sugar or replacing it with Splenda in a traditional recipe is unlikely to work. Instead, look for low-sugar pickle recipes or ones that call for Splenda.

Why can’t I just replace sugar with Splenda?

Fletcher Arritt, a food science professor at N.C. State University, explains that sugar and Splenda react differently with water when making jam, jelly, preserves or pickles. Sugar binds itself with the water, making it less available to microbes that can cause spoilage or make someone sick. Splenda does not bind as well with water, increasing the risk of microbial activity.

What about making jams and preserves with other sugar substitutes or artificial sweeteners?

Cooks can use honey, maple syrup, agave syrup and stevia with Pomona’s pectin or low-methoxyl pectins. The key is finding trusted recipes that call for such ingredients.

Vinton advises against using artificial sweeteners, such as aspartame and sucralose, because they become bitter when cooked and create an off flavor.


How can I be sure that I’m following safe canning practices?

Safety is one of the first topics McClellan, author of “Food in Jars” and “Preserving by the Pint,” addresses when she teaches people how to can. She explains that most jams, jellies, preserves and pickles are high-acid foods, which can be safely processed in a boiling water canner with no risk of botulism. “It is impossible for botulism to develop,” McClellan said. “I really stress it just isn’t going to happen.”

Let’s cover some basics to explain the science. There are two types of canning: boiling water bath canning, which is used to process high-acid foods, such as jams, jellies, preserves and pickles; and pressure canning, which is required for low-acid fruits and vegetables, meats, poultry and soups.

With high-acid foods, processing jars in a boiling water bath, which reaches temperatures of 212 degrees, is all that is needed to kill molds, yeasts and bacteria. With low-acid foods, pressure canning is required to reach a temperature of 240 degrees, the level at which harmful bacteria and botulism spores can be killed.

The key to safe canning is following professionally tested recipes, such as those from the National Center for Home Food Preservation ( and from authors you trust. “People are very afraid of preserving their own food,” Vinton says. “They don’t have to be. Just follow the recipe.”

What about the risk of botulism?

Botulism is only an issue when canning low-acid fruits and vegetables, such as green beans, corn, peas or asparagus in salted water, or when canning seafood, meat, poultry, soups or stews. Those foods do not contain enough acid, either naturally or from a pickling brine, to create an environment that is inhospitable to botulism spores. Those foods must be processed in a pressure canner to 240 degrees to kill the spores.

Since tomatoes are low-acid fruits, do they need to be pressure canned?

Tomatoes are borderline low-acid fruits and can be made safe to can in a boiling water bath with the addition of citric acid or lemon juice. The rule is to add 1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid per pint, or 2 tablespoons bottled lemon juice or 1/2 teaspoon citric acid per quart.

Is it safe to do “open-kettle canning?”

No. Open-kettle canning is an out-of-date practice in which home cooks would fill hot glass jars with hot jams, fruits and or pickles and brine, and then seal without processing.

Ben Chapman, a food scientist at N.C. State University, explains that processing the jars in a boiling water bath helps kill microbes in the food, vent out oxygen containing microbes and remove as much air as possible from jars to create a good seal – all essential for a safe product. Without that processing, microbes may be able to grow.

My grandmother used to use paraffin to seal her jams and jellies. Can I do the same?

No. Sealing jams or jellies with paraffin does not involve the added protection of boiling water bath canning that Chapman describes above. Plus, pinholes can develop in the paraffin to let in microbes.

How to avoid fruit float

Sherri Brooks Vinton’s “Put ‘em Up! Fruit,” described the dreaded fruit float that can strike even the most skilled canner. She explained that there are a few things to prevent fruit floating to the top of the jars: cook jams thoroughly, as dictated in the recipe, to break down fruit’s cell walls, allow jam to rest for 5 minutes before filling jars, do not process jars for longer than recipe says, and once the jars have sealed but are still warm, flip them over and let them sit for 30 minutes before storing them right-side up.


Just right strawberry preserves

Makes 3 1/2 to 4 half-pint jars

The key to this recipe is a Granny Smith apple. Once it’s grated directly into the berry-sugar mixture and offered a 2- to 24-hour maceration (rest period), the fruity syrup becomes suffused with the apple’s natural pectin. Make sure to use about three-quarters perfectly ripe berries and the rest underripe; the latter have more natural pectin.

You will need a candy thermometer and 4 sanitized half-pint jars with new lids and rings; see the Notes below.

From Cathy Barrow for The Washington Post.


3 pounds (about 2 quarts) strawberries, hulled

3 cups granulated sugar (organic or raw may be substituted, but use weight, not volume; 26.4 ounces)

Juice of 1 lemon

1 Granny Smith apple

1/2 teaspoon unsalted butter (optional)


Combine the strawberries, sugar and lemon juice in a large mixing bowl; use a potato masher or broad, nonflexible spoon to mash the fruit into the sugar just enough so that some larger pieces of berry remain.

Use the large-holed side of a box grater to grate the (unpeeled) apple directly into the bowl, turning it once the core is exposed. Stir to incorporate thoroughly. Cover and refrigerate for 2 to 24 hours.

Pour the mixture into a colander set over a heavy-bottomed 5-quart pot or preserving pan. Stir, encouraging the collected syrup to fall into the pan or pot. Remove the colander, seating it inside the bowl to capture any remaining syrup; add that to the pan or pot as needed. Leave the solids in the colander while you cook the syrup.

Clip the candy thermometer onto the preserving pan or pot; cook over high heat to bring the syrup to 220 degrees, the soft-ball stage in candymaking. The syrup will foam and rise up, so stir it from time to time. Add the berry mixture to the syrup, stirring as the preserves return to a rolling boil. The preserves will foam and rise up as the water boils away and the set is achieved. Once the foam is nearly gone, the jam will be done. Turn off the heat and test the set (see Note 1, below).

Once the set has been achieved, add the butter, if desired. Stir well and thoroughly without scraping the sides or bottom of the pan or pot until the last bits of foam have disappeared.

Ladle the preserves into the sanitized jars, leaving 1/2 inch of head space. Run a chopstick or flat plastic knife along the inside of the jars to dislodge any air bubbles. Clean the rim of each jar, place the warmed lids and finger tighten the rings (not too tightly). Process in the boiling water bath for 10 minutes (see NOTE 2, below). Turn off the heat and use a jar lifter to transfer the jars to a clean, folded dish towel to cool for several hours.

Label and date the sealed jars. Store in a cool, dark place for up to 1 year. Refrigerate after opening.

Note 1: There are three ways to test the set. The sheeting test entails stirring the preserves, then lifting the spoon to watch the jam sheet off the spoon, flowing slowly and collecting along the bottom of the spoon before languidly dripping back into the pot. It should look like jam, not like syrup. The sheeting test takes a practiced eye.

The cold plate test is a surefire method of testing the set. Before beginning to cook the jam, tuck 3 small plates and three spoons into the freezer. Once the preserves seem to be set, use a cold spoon to place a tablespoon or so of jam on the plate. It should set instantly. Press against the blob of jam. Does it resist just a bit? Wrinkle a little? It’s done.

The third method is the lazy cook’s cold-plate test. Remove the preserves from the heat and cool for 3 to 5 minutes. Press against the surface of the jam. Does it resist just a bit? Wrinkle a little? The jam is ready.

For jam that is not yet set, return the preserves to the stove; cook for 2 to 5 minutes at a strong, hard, foamy boil that rises up no matter how much you stir; then test again. Stop and start the cooking process as many times as necessary until you are satisfied with the set. The jam will set further as it sits.

Note 2: Water-bath canning safely seals high-acid, low-pH foods in jars. The time for processing in the water bath is calculated based on the size of the jar and the consistency and density of the food. For safety’s sake, do not alter the jar size, ingredients, ratios or processing time in any canning recipe. If moved to change any of those factors, simply put the prepared food in the refrigerator and eat within a week.

Fill a large canning kettle or deep stockpot two-thirds full with water. To keep the jars from rattling against the pot, place a rack in the pot. (A cake rack works well; a folded dish towel is equally effective.) Sanitize the jars in a short dishwasher cycle or by boiling them in a canning kettle or pot for 10 minutes. Fill a small saucepan with water and add the rings. Bring to a boil over high heat, slip in the lids and turn off the heat.

Use a jar lifter or tongs to lower the filled, sealed jars into the boiling water bath, keeping them upright. When all of the jars are in place, the water should be 1 to 2 inches above the jar tops. Add water as needed. Bring the water to a low boil before starting the timer for processing.

At the end of processing, turn off the heat and let the jars sit in the water bath until the boiling has stopped. That will reduce siphoning, in which the food burbles up under the lid, breaking the seal. Use the jar lifter or tongs to transfer the jars to a folded towel, keeping them upright. Leave the jars until they have completely cooled, at least 12 hours. Remove the rings and test the seal by lifting each jar by the lid. The lid should hold fast. Label and store in a cool, dry, dark space.

Per tablespoon (based on 4 half-pint jars): 45 calories, 0 g protein, 11 g carbohydrates, 0 g fat, 0 g saturated fat, 0 mg cholesterol, 0 mg sodium, 0 g dietary fiber, 11 g sugar


Rhubarb mango chutney

Makes 3 half-pint jars

If fresh mango is unavailable, substitute an equal amount of dried mango, dried pineapple or golden raisins. The serrano chili makes a spicy chutney.

You will need a candy thermometer, 3 sanitized half-pint jars with new lids and rings, and a jar lifter or coated tongs. See Note 2 under the recipe at left for water-bath canning information.

For The Washington Post from Cathy Barrow, author of “Mrs. Wheelbarrow’s Practical Pantry: Recipes and Techniques for Year-Round Preserving” (to be published in November).


1 pound ruby red rhubarb, trimmed, then diced (about 3 cups)

Flesh from 2 large mangoes, diced (scant 1 cup)

1/2 cup diced red onion

1/3 cup crystallized ginger, diced

1 small clove garlic, minced

1/2 serrano chili pepper, seeded and sliced (optional)

2/3 cup granulated sugar (7 ounces by weight if substituting organic or raw)

2/3 cup packed light brown sugar

1/2 cup apple cider vinegar

1/2 teaspoon yellow mustard seed

1/4 teaspoon coriander seed

1/4 teaspoon kosher salt


Combine the rhubarb, mango, red onion, crystallized ginger, garlic and serrano, if using, in a heavy, nonreactive 5-quart pan. Sprinkle the granulated and brown sugars over the surface of the fruit, then add the vinegar, mustard seed, coriander seed and salt. Stir well until thoroughly incorporated. Bring to a boil over medium-high heat, stirring frequently; cook the mixture for about 35 minutes or until it has the consistency of chunky applesauce. Be careful; the hot mixture will spit and sputter.

Turn off the heat to evaluate the consistency. Allow the chutney to cool for 3 to 5 minutes, then press against the surface with a spoon. The chutney should wrinkle slightly. If it is still watery, return it to the heat and boil for 5 minutes before testing again. Continue to cook and test as needed.

Ladle the chutney into the sanitized jars, leaving 1/2 inch of head space. Run a chopstick or plastic knife along the inside of each jar and through the chutney to dislodge any air bubbles. Clean the rim of each jar, top with the warmed lids and finger-tighten the rings (not too much). Process in the boiling water bath for 10 minutes. Turn off the heat and use the jar lifter or tongs to transfer the jars to a clean, folded dish towel to cool for several hours.

Label and date the sealed jars. Store in a cool, dark place for up to 1 year. Refrigerate after opening.

Per tablespoon: 30 calories, 0 g protein, 8 g carb., 0 g fat, 0 g sat. fat, 0 mg chol., 10 mg sodium, 0 g fiber, 7 g sugar

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