I’ve had my share of canning disasters. Canning isn’t complicated, but upset the chemistry of pectin and sugar or skip a step in the process, and you may find yourself in, well, a jam.
Theresa Loe is the resident canning expert and associate producer for PBS’s Growing a Greener World. She’s been canning food all her life, and her blog, Living Homegrown Fresh, covers food preservation as well as urban gardening. Loe says she first learned how to can at her mother’s apron strings, but she extended that knowledge through training in a master food-preserver program, attending culinary school, and keeping up with the latest USDA recommendations and guidelines. Here’s her advice for avoiding or, when possible, fixing canning efforts that have gone awry.
1. Problem: Jelly Won’t Gel
“Jellies ‘gel’ because of a perfect ratio between the acid, pectin and sugar of the mixture. If the proper ratio isn’t achieved, you get a runny jelly,” says Loe. That ratio can be upset when the fruit you’re using doesn’t have enough natural pectin, which can happen with overripe fruit, or when you’ve reduced the amount of sugar or skipped the lemon juice that some recipes call for. You must have a perfect balance of sugar, acid and pectin.
To ensure gelled jellies, Loe suggests following a proven, reliable recipe to the letter—without adjustments. Make sure your fruit is picked at its prime, before it gets too ripe—the pectin level of fruit drops as the fruit ripens.
If you have a batch that doesn’t gel, you have a couple of options.
“If it’s a small batch, use it as syrup on pancakes, waffles and in cooking. I usually only remake runny jelly if I have a large batch or two that didn’t work,” says Loe.
If you decide to re-batch, you’ll need to open the jars and pour all of the contents back into your pot; add sugar, lemon juice and pectin; cook it again; and reprocess it.
“It usually works,” says Loe, but she cautions that you might end up with a rubbery consistency after reprocessing.
Don’t rush to judgment. Some jellies and jams take a little longer to set than others. If it still has a syrupy consistency after it’s completely cooled, then it probably won’t set up, and you can try re-batching it.
2. Problem: Jelly Gels Too Much
Too much pectin or overcooking your jelly or jam will cause it to be overly firm.
“People are surprised by the delicate balance between the ratios of sugar, acid and pectin. If you have too much pectin compared to the sugar and acid in the mix, you get overly firm jelly or jam,” says Loe. “Also, if your fruit was [not fully ripe] and you added commercial pectin, you may have upset the ratio.”
Make sure your fruit is at its prime, or that you have a mixture of less-mature fruit combined with ripe fruit. And be careful to time your cooking precisely.
“If you cook the mixture too long,” explains Loe, “you evaporate too much of the water, and the jam or jelly gets too firm.”
If your jelly or jam ends up too firm, there’s really no fix.
“You can use it for cooking rather than as a spread,” suggests Loe. “If you place some in a small saucepan with a little water and melt it down, you can use it in sauces or as a topping for waffles or ice cream. But you really can’t re-can it.”
3. Problem: Lids Don’t Seal or Release Their Seal
Often, this will happen if there’s a nick in the jar rim or if you don’t completely wipe the food from the rim. The rim needs to have complete contact with the lid to seal properly.
Another reason is too much headspace.
“Headspace is the space between the food and the top of the jar,” says Loe. “Too much space can make it difficult for the jar to create the vacuum seal. The air inside the jar reaches a certain temperature during processing, cools and then escapes, causing the vacuum seal that sings out that ‘ping.’ But only so much air can come out successfully. If there’s too much headspace, there won’t be a vacuum, or it will be a weak vacuum that will gradually release on the shelf.”
Lid manufacturers also recommend placing your lids in a pot, covering lids with water and bringing the water to a simmer, then keeping the lids hot until you’re ready to use them. Do not boil your lids: This can cause the seals to fail.
The fix: “If the problem was discovered within 24 hours, you can reprocess the food,” says Loe.
Remove the band and lid, and check the top of the jar for nicks. If there are any nicks, put the food in a new, sterile jar. Wipe down the jar’s rim to remove any food particles and check the headspace to be sure you’re following the recipe’s guidelines. Add a new lid and band, and reprocess the jars for the full amount of time.
4. Problem: Canning Process Is Interrupted by a Power Outage
In this case, chalk one up to Murphy’s Law.
If you have power within 24 hours, start the processing time over as soon as the power comes back on, and process the jars for the full time all at once. It may affect the food’s texture (i.e., pickles may lose crispness), but it depends on the food and the processing time.
5. Problem: Fruits Lose Their Texture or Color
Discoloration may just be the result of natural changes that take place in certain fruits during processing. Using water or fruit juice for packing fruit (instead of sugar syrups) may not keep the fruit’s color, but the flavor will still be good. Overripe fruit won’t hold up to processing and storage as well as fruit processed at its peak.
After the fact, there’s not much you can do, but there are a few steps you can take to preserve color and texture before canning.
“Sugar syrups will best preserve the shape, color and flavor of canned fruit,” says Loe. “However, many of us don’t want to use sugar syrup. If you use fruit juice or water, you might get a slightly less-appealing color, but the flavor will be good and the food should still be safe.”
If you’re canning a fruit that browns (apples or peaches, for example), Loe suggests adding ascorbic acid to the fruit by following the directions on the container. It will prevent discoloration and preserve a brighter appearance.
“Testing has shown that ascorbic acid works better than just lemon juice,” she says. “Ascorbic acid is just powdered Vitamin C—but it’s not the same thing as citric acid.”
6. Problem: Pickles Aren’t Crisp
Starting with less-than-fresh cucumbers or using a salad cuke for pickles instead of pickling cucumber varieties can result in less-than-crisp pickles.
There’s nothing you can do to put the crisp into the pickle once it’s made, but there are some pre-pickling steps you can take. First, plant or buy pickling varieties—not salad cucumbers. And the cucumbers you use must be fresh.
“The fresher the better,” advises Loe. “The best pickles are made with cucumbers that are less than 24 hours off the vine. Every day over 24 hours will cause you to lose crispness.” Choose cucumbers that are firm and dark green, and slice off the blossom end of the cucumber before processing. (The blossom scar has enzymes that cause softening.)
7. Problem: Floating Fruit
There are a lot of causes for this very common problem. Packing jars too loosely, using overripe fruit (the pectin content is lower and pectin helps hold the fruit in suspension), using too much sugar in the syrup (the fruit density can be lighter than the syrup if a heavy syrup is used), over-processing, and raw-packing fruit instead of hot-packing can all cause fruit to float to the top of the jar.
“The fruit is fine,” says Loe. “It’s perfectly safe to eat and will store well on the shelf.” But there are steps you can take that will prevent floating fruit.
Use firm, ripe (but not overripe) fruit, pack the fruit into the jars firmly without smashing, use a light or medium syrup rather than a heavy syrup, use the proper processing time in the recipe, and use the hot-pack method rather than the raw-pack method.
“Raw-pack is when you fill the jar with unheated fruit and add a hot liquid before processing,” Loe explains. “Hot-pack is where you heat the fruit in a liquid and then fill the jars and process. As the fruit is heated, the excess air inside the fruit escapes and this prevents floating later. You can heat the fruit in water or fruit juice, and it won’t over-sweeten the fruit. Both [raw and hot] methods are safe, but hot-packed fruits tend to hold their color and texture better on the shelf.”
8. Problem: Jars Leak During Processing or Cooling
If you notice color in your water bath (pink water for cherries, for example) or the sides of your jars are sticky after cooling, chances are the jars were overfilled. If there is too little headspace, some of the juice will bubble out during the processing. This can also happen if the food was raw-packed instead of hot-packed into the jar.
As long as there’s still enough liquid in the jar to cover most of the food, it should be fine. Carefully wash off the stickiness, and set the jars on the shelf. Keep in mind that any food sitting above the liquid will discolor—though it should still be safe to eat. “Be sure to check the seal just before opening,” cautions Loe. “Sometimes the food seeping out can cause the seal to fail while sitting on the shelf. Food particles under the lid slowly release the vacuum seal. If you pull a jar off the shelf and it is unsealed, don’t eat the contents—you have no idea how long it’s been unsealed.”
If half or more of the syrup is gone after sealing, store the food in the refrigerator and use it within a few days.
To prevent it from happening again, always use proper headspace when filling a jar, and use a hot-pack method instead of a raw-pack.
9. Problem: Air Bubbles Occur After Processing
“Air bubbles are just pockets of air that didn’t get released during packing or processing. Air clings to the food during processing, and sometimes even our best efforts won’t dislodge them all,” says Loe. “As long as the bubbles aren’t moving on their own, which would indicate bacterial fermentation, they’re perfectly safe—though you may get some discoloration where they sit on the fruit.” If you suspect bacterial fermentation, discard the food.
After you fill your jars (and before processing), run a rubber spatula or a chopstick around the inside edges of the jar to release all the air bubbles. (Don’t use a metal knife, as it may scratch the jar.) Then check the headspace again. If releasing the bubbles lowers the liquid level, add more liquid for proper headspace, then continue with your processing.
As Loe’s advice suggests, many canning disasters can be avoided by carefully following the basic rules and steps, as well as using proven, reliable recipes. If you’re not sure about a recipe, or you’ve run into a canning disaster, don’t hesitate to contact your extension office for advice.
This article originally appeared in the May/June 2011 issue of Hobby Farm Home.