Food Safety Feature Articles
Put a Lid on Canning Problems
Janet Hackert, Regional Nutrition and Health Education Specialist, University of Missouri Extension
There’s more to canning than putting a lid on a jar and getting it to seal, but if it doesn’t seal, it is a problem! Understanding canning lids can help prevent some problems.
The recommended lid for canning is made up of two parts
– the flat and the ring band. Always use new flats.
Clean ring bands in good condition (no rust and not
bent) can be reused.
The flat is just that – a flat piece of metal, with a
food-safe liner and a ring of sealing compound. As the
jar and two-piece lid are heated during canning, the
sealing compound changes shape slightly to conform to
the lip of the jar. When the jar cools, a strong seal
can be made. This seal keeps food safe that has been
made safe by canning for the proper time, temperature
and pressure (if needed).
Unlike lids of years ago, new lids require a lighter
touch when closing the jar for canning. Some time ago,
major canning lid companies redesigned their lids. Lids
today need only be screwed on gently. At
freshpreserving.com, Jarden Corporation, maker of Ball
and Kerr lids, recommends, “apply bands just until a
point of resistance is met – fingertip tight.” If ring
bands are screwed on too tightly, the lids will buckle
and may forfeit the seal. If bands are not screwed on
tightly enough, a seal may not form.
Although it is important to keep items used for canning
clean, it is not a good idea to boil canning flats to
sterilize them. The sealing compound used these days
will soften when boiled. With this change happening
prior to the actual canning process, when the lids on
the jars are then processed at canning temperatures,
they will form a seal prematurely. Buckling occurs and
food is spoiled.
After canning is complete and jars are cool, remove the
ring band for storage. Ring bands left on in storage may
rust shut.
Store jars in a dry, dark, cool place, ideally 50-70°F.
Dampness may corrode metal lids, break seals and spoil
food.
For more information, check the guide sheet,
Steps to Success in Home Canning GH 1452, or read
the Frequently Asked Questions page of Jarden Home
Brands ©, at
http://www.freshpreserving.com/pages/faq/42.php, or
call Janet Hackert at 660-425-6434 or
HackertJ@missouri.edu.
Last update:
Tuesday, August 19, 2008
 |
Site Administrator: |
|
|
|
