Answers to common canning questions
06/03/2014 5:00 PM
06/03/2014 5:05 PM
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 five cups of mashed fruit and seven 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 can without fear.
I heard these concerns again and again these last several months at events for my first cookbook, “Pickles & Preserves: A Savor the South Cookbook.” With strawberry season in full swing and peach season not far off, here are answers to your most common canning questions with an assist from fellow canning cookbook authors, food scientists and home economists.
Q: Why do recipes for jam, jelly and preserves call for so much sugar?
A: 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, will not have that bright, glossy color and ideal texture or last as long once opened.
Q: Can I make jams or preserves with less sugar or no sugar?
A: 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 Earth Fare, 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.
Q: Can I make sweet pickles with less sugar?
A: 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.
Q: Why can’t I just replace sugar with Splenda?
A: 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.
Q: What about making jams and preserves with other sugar substitutes or artificial sweeteners?
A: 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.
Q: How can I be sure that I’m following safe canning practices?
A: 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.”
Q: What about the risk of botulism?
A: 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.
Q: Since tomatoes are low-acid fruits, do they need to be pressure canned?
A: 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.
Q: Is it safe to do “open-kettle canning?”
A: 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 in a boiling water bath.
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 the jars to create a good seal – all essential for producing a safe product. Without that processing, he explains, microbes may be able to grow.
Q: My grandmother used to use paraffin to seal her jams and jellies. Can I do the same?
A: 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 microbes into the jams or jellies.
This is what I tell people who ask about open-kettle canning and using paraffin: “Just because your grandmother did it doesn’t make it safe. Your grandparents rode around in cars without seat belts. We know more know about food safety than they did and we should be smart enough to use that knowledge.”
Q: More questions?
A: If you have a canning question that has not been answered here, let me know. I’ll tackle some of them in an upcoming column.
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