Canning produce is a relatively simple way to preserve a homegrown harvest. Fresh fruits and vegetables can be pickled, processed into jams or jellies, packed in syrup or otherwise prepared to be sealed and stored at room temperature for use when the harvest is not so bountiful. Unfortunately, some of the rules of canning were never meant to be broken. Before putting up this year’s harvest, take a look at these common canning mistakes to avoid turning the “can” into a “can’t” in home canning.
Even a jar that looks clean may harbor bacteria that will contaminate canned food with short processing times. Sterilize jars before canning by washing thoroughly with soap and water and then boiling empty jars for 15 minutes. Some dishwashers also offer a “sterilize” mode to simplify the process.
One of the great conveniences of canning is that jars may be used over and over, but eventually jars will show signs of wear. Inspect jars for chips or cracks before beginning a canning project. Even the smallest nick can result in breakage during processing or failure to seal properly.
Canned goods sealed in a water bath rely on acidity in the produce to keep bacteria at bay. Low acid produce can get an acidic boost using citric acid, vinegar, etc. to be canned using this method. Pressure canning reaches much higher temperatures, killing off bacteria and making it the safest way to can low-acid foods like corn, green beans or even meat without augmenting the acid content. Improper canning of low acid food poses the most serious health risks when home canning, Bacteria like botulism can thrive when low acid food is stored in an absence of air if not destroyed by pressure canning at temperatures of 240 degrees or higher.
For most canning projects, jars should be filled no higher than ¼-½ inch from the top. Overfilled jars are likely to expel liquid during processing, leading to discoloration of canned produce or failure to seal.
A little extra headspace may or may not impact a successful seal, but if produce is not completely submerged in liquid it can cause discoloration and possible texture and flavor issues.
Filling jars for canning can be a messy business. Before capping jars for processing, be sure to wipe the rim of the jar clean. Food trapped between the rim of the jar and the lid can result in an imperfect seal, subjecting food to spoilage.
While jars and bands may be re-sterilized and used many times, lids are single-use only. Although it may look fine, once a lid has been indented by the rim of jar, a second use is unlikely to yield the *pop* while cooling that signifies a successful seal.
Rusty or dented bands are less likely to hold the lid snugly, resulting in failure to seal.
Canning bands should be finger tightened to be snug. A loose band may result in loss of liquid during processing or an unsuccessful seal.
It is a good practice to sterilize jars shortly before canning or to place in a low temperature oven while preparing to can. Cold jars subjected to the rolling boil of a water bath canner are much more likely to break.
Incorrect Processing Time
Different foods and even altitudes require adjustments to the processing time when water bath canning. Insufficient processing time may not force all of the air from the jar. Processing too long can lead to discoloration or negatively impact food texture. Always consult a recipe, canning guide or visit the National Center for Home Food Preservation before canning.
Mishandling Hot Jars
Lifting jars by the lid after water bath processing can break the seal and also presents a burn risk if dropped. Using a jar lifter (an inexpensive tool for gripping jars to safely remove from a water bath) is always recommended. Once jars have been removed from bath, allow to cool completely before removing bands.
If you’ve done everything right and still end up with disappointing results, consider the produce. Underripe or overripe produce will not improve when canned. Select only ripe, unblemished produce when preparing to preserve the harvest.
Originally: 13 Canning Fails