Canning your own food in and Urban Environment
Canning page (2) Two
Cooling Jars and Testing Jar Seals
Cooling jars

When you remove hot jars from a canner, do not retighten their jar lids. Retightening of hot lids may cut
through the gasket and cause seal failures. Cool the jars at room temperature for 12 to 24 hours. Jars
may be cooled on racks or towels to minimize heat damage to counters. The food level and liquid volume
of raw-packed jars will be noticeably lower after cooling. Air is exhausted during processing and food
shrinks. If a jar loses excessive liquid during processing, do not open it to add more liquid. Check for
sealed lids as described below.


















Testing jar seals
After cooling jars for 12 to 24 hours, remove the screw bands and test seals with one of the following
options: Option 1.  Press the middle of the lid with a finger or thumb. If the lid springs up when you
release your finger, the lid is unsealed.  
Option 2.  Tap the lid with the bottom of a teaspoon. If it makes a dull sound, the lid is not sealed. If food
is in contact with the underside of the lid, it will also cause a dull sound. If the jar is sealed correctly, it
will make a ringing, high-pitched sound.  
Option 3.  Hold the jar at eye level and look across the lid. The lid should be concave (curved down
slightly in the center). If center of the lid is either flat or bulging, it may not be sealed.  
















Reprocessing unsealed jars
If a lid fails to seal on a jar, remove the lid and check the jar-sealing surface for tiny nicks. If necessary,
change the jar, add a new, properly prepared lid, and reprocess within 24 hours using the same
processing time. Headspace in unsealed jars may be adjusted to 1-½ inches and jars could be frozen
instead of reprocessed. Foods in single unsealed jars could be stored in the refrigerator and consumed
within several days.


Storing
Home Canned Foods
Testing Jar Seals
After cooling jars for 12 to 24 hours, remove the screw bands and test seals with one of the following
options:

Option 1: Press the middle of the lid with a finger or thumb. If the lid springs up when you release your
finger, the lid is unsealed.

Option 2: Tap the lid with the bottom of a teaspoon. If it makes a dull sound, the lid is not sealed. If food
is in contact with the underside of the lid, it will also cause a dull sound. If the jar is sealed correctly, it
will make a ringing, high-pitched sound.

Option 3: Hold the jar at eye level and look across the lid. The lid should be concave (curved down
slightly in the center). If center of the lid is either flat or bulging, it may not be sealed.

Reprocessing Unsealed Jars
If a lid fails to seal on a jar, remove the lid and check the jar-sealing surface for tiny nicks. If necessary,
change the jar, add a new, properly prepared lid, and reprocess within 24 hours using the same
processing time. Headspace in unsealed jars may be adjusted to 1½ inches and jars could be frozen
instead of reprocessed. Foods in single unsealed jars could be stored in the refrigerator and consumed
within several days.

Storing Canned Foods
If lids are tightly vacuum sealed on cooled jars, remove screw bands, wash the lid and jar to remove
food residue; then rinse and dry jars. Label and date the jars and store them in a clean, cool, dark, dry
place. For best quality, store between 50 and 70 °F. Can no more food than you will use within a year.

Do not store jars above 95° F or near hot pipes, a range, a furnace, in an uninsulated attic, or in direct
sunlight. Under these conditions, food will lose quality in a few weeks or months and may spoil.
Dampness may corrode metal lids, break seals, and allow recontamination and spoilage.

Accidental freezing of canned foods will not cause spoilage unless jars become unsealed and
recontaminated. However, freezing and thawing may soften food. If jars must be stored where they may
freeze, wrap them in newspapers, place them in heavy cartons, and cover with more newspapers and
blankets.

Identifying and Handling Spoiled Canned Food
Do not taste food from a jar with an unsealed lid or food that shows signs of spoilage.
You can more easily detect some types of spoilage in jars stored without screw bands. Growth of
spoilage bacteria and yeast produces gas which pressurizes the food, swells lids, and breaks jar seals.
As each stored jar is selected for use, examine its lid for tightness and vacuum. Lids with concave
centers have good seals.

Next, while holding the jar upright at eye level, rotate the jar and examine its outside surface for streaks
of dried food originating at the top of the jar. Look at the contents for rising air bubbles and unnatural
color.

While opening the jar, smell for unnatural odors and look for spurting liquid and cottonlike mold growth
(white, blue, black, or green) on the top food surface and underside of lid.

Spoiled low-acid foods, including tomatoes, may exhibit different kinds of spoilage evidence or very
little evidence. Therefore, all suspect containers of spoiled low-acid foods, including tomatoes, should
be treated as having produced botulinum toxin and handled carefully in one of two ways:

If the swollen metal cans or suspect glass jars are still sealed, place them in a heavy garbage bag. Close
and place the bag in a regular trash container or bury it in a nearby landfill.
If the suspect cans or glass jars are unsealed, open, or leaking, they should be detoxified before
disposal.
Detoxification process: Carefully place the suspect containers and lids on their sides in an 8-quart
volume or larger stock pot, pan, or boiling-water canner. Wash your hands thoroughly. Carefully add
water to the pot. The water should completely cover the containers with a minimum of a 1-inch level
above the containers. Avoid splashing the water. Place a lid on the pot and heat the water to boiling.
Boil 30 minutes to ensure detoxifying the food and all container components. Cool and discard the
containers, their lids, and food in the trash or bury in soil.

Thoroughly scrub all counters, containers, and equipment including can opener, clothing, and hands
that may have contacted the food or containers. Discard any sponges or wash cloths that may have been
used in the cleanup. Place them in a plastic bag and discard in the trash.