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Cracked Jars: Reading
Between the Lines
Welcome to the first issue of Quality for Keeps for 2005. We are looking
forward to bringing you the latest and safest USDA-based information.
This June, Missouri Extension specialists are participating in a food
preservation update led by Elizabeth Andress, PhD, Director of the
National Center for Food Preservation. We will be sure to share all her
tips with you later this summer.
For now, it is time to inventory those supplies, look
for new recipes (from USDA, Extension or Ball) and locate sources for
any special ingredients. This issue will help with updated contact
information for suppliers. We also have a few tips for those that
frequent garage sales for supplies.
Now is also time to remind those with dial gauges on their pressure
canners to get them tested before canning season starts. Contact your
county Extension office to see if they can provide this service. It is
usually only a few dollars…. and buys a lot of peace-of-mind to know
that your hard work has resulted in a safely canned product. Every year
a third to half the canner gauges we test are “off” enough to require
replacement. In fact, if you are considering buying a pressure canner,
we suggest looking for one that regulates using weights since these
never require calibration or testing.
And, as long as we are on the subject of equipment we might as well
review a common cause for disappointment – broken jars. Canning jars can
crack or break for a variety of reasons. The cause can often be
determined by recognizing the style of crack.
Thermal shock. Crack runs around the base of the lower part of
the jar, and sometimes extends up the side. To prevent this:
•Avoid sudden temperature changes, such as putting a hot jar on a cool
or wet surface, putting hot food or liquid in a room-temperature jar, or
setting jars directly on the bottom of the canner. Instead, keep jars in
hot water until filled, use a rack in the canner and place hot jars on a
towel or cutting board instead of directly on the counter to cool.
•Avoid using metal knives or spatulas to remove air bubbles or steel
wool pads to clean jars. They may damage the glass and make it
susceptible to thermal shock.
Internal pressure break. A vertical crack on the side of the jar
which divides and forks into two fissures. To prevent pressure cracks:
•Don’t use the oven method for processing jars.
•Keep heat steady during processing.
•Avoid reducing canner pressure under running water or lifting the
pressure control or petcock before pressure drops to zero at room
temperature.
Impact break. Starts at the point of impact
and fissures radiate from the point of contact. To prevent:
•Handle jars carefully. Jars that survive being dropped, hit or bumped
are susceptible to breakage later. Test new jars that may have been
mishandled by immersing them in room-temperature water, bring to a boil
and boil 15 minutes.
•Avoid the use of metal tools to remove air bubbles.
•Avoid using very old jars. Jars have a life expectancy of about 10
years.
Other April 2005 Articles:
Can Splenda®
Be Used in Preserving Foods?
Addresses for Suppliers
Questions & Answers
Cynthia
Fauser
fauserc@missouri.edu
Nutrition Specialist
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April
2005
