Troubleshooting Canning Problems
Sometimes, even those who have been home canning for years may run into problems with their food-filled jars. Some problems are related to the condition of the jars or lids and/or how they were filled. Others relate to spoilage of the food or changes the food may have undergone during processing. We present the following information to help you troubleshoot what may have gone wrong if you encounter a problem.
Jars Won't Seal
The most common problem encountered by home canners is jars that do not seal properly. If jars do not seal during cooling, the food may be repacked with a new lid and the jars processed again for the entire amount of processing time in the recipe. If only one jar did not seal, refrigerate it and use the contents within 2 days.
There are several causes that often prevent jars from sealing. These include: overfilling of the jar, chipped jar rims, particles of food on the jar rims (from improperly wiped jars) coming between the surface of the rim and the sealing compound in the lid, lids being too hot or too cold, scratches across the sealing compound in the lid, screw bands being tightened after jars are removed from the canner thus breaking the seals, bent or rusty screw bands not holding the lid against the jar rim tightly enough during processing.
Other problems are simply changes in the food, which change the cosmetic appeal of it but do nothing to the nutritional quality. When sediment appears in the bottoms of jars, it may simply be minerals in the water used for filling the jars or precooking the food. If the food contains a significant amount of starch, such as corn or beans, some of the starch may have settled out of the food. If there is sediment in a jar of fruit, the fruit was most likely overripe at the time of processing.
When table salt containing an anti-caking ingredient is used instead of the proper pickling salt, you may find sediment at the bottom of your jar of pickles. Foods may change color because they were not processed long enough to kill color-changing enzymes. Over processing can cause color changes too. Color changes in fruits, such as pears or peaches, are most likely due to them being left untreated with an ascorbic acid color keeper during preparation. Some foods with lots of color in them, like beets, may leach some of their color into the surrounding liquid or syrup. Contact with air may discolor food if the jar was not filled with enough liquid and the top portion of food dries out or if air bubbles are not removed prior to processing. Food stored in a warm room or exposed to strong light may also discolor.
If food floats to the top of the jar, it may have been packed too loosely or processed too long. If fruit, it may have been too ripe or the syrup may be too heavy for it. Raw-packed food that has been left uncooked tends to float more than partially cooked food. Uncooked food contains more air than cooked food. Liquid levels may be too low after processing if jars were too full or packed too tightly. This causes the food to boil over during processing and a siphoning action occurs. Liquid may be too low if air bubbles are not removed before processing. Sometimes, starchy foods will absorb water that creates lower liquid levels. Processing problems, such as fluctuating pressure within a pressure canner or water less than one in above the tops of jars in a water-bath canner also can cause low liquid levels in the finished jars.
Spoilage of food is a serious problem, which can result in food poisoning. If food was underprocessed, yeast and toxin causing bacteria may not have been totally destroyed. Some toxin-producing microorganisms can grow within an airtight jar. Inspect each jar of home canned food carefully before consuming the contents. Discard the food if there are patches of mold on it or if it is foamy or murky in appearance. A leaking jar should also be discarded. The food should smell pleasant and like the food that was canned. If it does not smell or look right, throw it out.
Bacteria that cause botulism toxin can be present in a sealed jar without changing the look or smell of the food if the jars were processed incorrectly. If you suspect your home canned food may contain botulism toxin, boil it uncovered for 10 minutes (20 for spinach and corn) to destroy the toxin. If it has spoiled, an unpleasant odor will most likely be produced. If it smells OK after boiling it is safe to eat, but "when in doubt, throw it out" still applies. Never taste foods with low acid content directly from the freshly opened jar. Home canned foods spoil when processed incorrectly.
Pressure in the pressure canner may not have been properly maintained at 10 pounds during processing either because the gauge was not accurate, the heat under the canner became too low and pressure dropped or no altitude correction was made to the processing time at altitudes above 2,000 feet. Air may not have been sufficiently exhausted from the pressure canner before the weight was placed over the vent to build the pressure up. In a water-bath canner, the water may not have been at a full boil for the entire processing time or the water level dropped below the tops of the jars.
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