Recommended Canners (Part 2 of 3)

INGREDIENTS

INSTRUCTIONS

Pressure Canners
Pressure canners for use in the home have been extensively redesigned in
recent years. Models made before the 1970's were heavy-walled kettles with
clamp-on or turn-on lids. They were fitted with a dial gauge, a vent port
in the form of a petcock or counterweight, and a safety fuse. Modern
pressure canners are lightweight, thin-walled kettles; most have turn-on
lids. They have a jar rack, gasket, dial or weighted gauge, an automatic
vent/cover lock, a vent port (steam vent) to be closed with a counterweight
or weighted gauge, and a safety fuse.
Pressure does not destroy microorganisms, but high temperatures applied for
an adequate period of time do kill microorganisms. The success of
destroying all microorganisms capable of growing in canned food is based on
the temperature obtained in pure steam, free of air, at sea level. At sea
level, a canner operated at a gauge pressure of 10.5 lbs. provides an
internal temperature of 240 degrees F.
Two serious errors in temperatures obtained in pressure canners occur
because:
* Internal canner temperatures are lower at higher altitudes. To correct
this error, canners must be operated at the increased pressures specified
in this publication for appropriate altitude ranges.
* Air trapped in a canner lowers the temperature obtained at 5, 10, or 15
pounds of pressure and results in underprocessing. The highest volume of
air trapped in a canner occurs in processing raw-packed foods in dial-gauge
canners. These canners do not vent air during processing. To be safe, all
types of pressure canners must be vented 10 minutes before they are
pressurized.
To vent a canner, leave the vent port uncovered on newer models or manually
open petcocks on some older models. Heating the filled canner with its lid
locked into place boils water and generates steam that escapes through the
petcock or vent port. When steam first escapes, set a timer for 10 minutes.
After venting 10 minutes, close the petcock or place the counterweight or
weighted gauge over the vent port to pressurize the canner.
Weighted-gauge models exhaust tiny amounts of air and steam each time their
gauge rocks or jiggles during processing. They control pressure precisely
and need neither watching during processing nor checking for accuracy. The
sound of the weight rocking or jiggling indicates that the canner is
maintaining the recommended pressure. The single disadvantage of
weighted-gauge canners is that they cannot correct precisely for higher
altitudes. At altitudes above 1,000 feet, they must be operated at canner
pressures of 10 instead of 5, or 15 instead of 10, PSI.
Check dial gauges for accuracy before use each year and replace if they
read high by more than 1 pound at 5, 10, or 15 pounds of pressure. Low
readings cause over-processing and may indicate that the accuracy of the
gauge is unpredictable. Gauges may be checked at most county Cooperative
Extension offices.
Handle canner lid gaskets carefully and clean them according to the
manufacturer's directions. Nicked or dried gaskets will allow steam leaks
during pressurization of canners. Keep gaskets clean between uses. Gaskets
on older model canners may require a light coat of vegetable oil once per
year. Gaskets on newer model canners are pre-lubricated and do not benefit
from oiling. Check your canner's instructions if there is doubt that the
particular gasket you use has been pre-lubricated.
Lid safety fuses are thin metal inserts or rubber plugs designed to relieve
excessive pressure from the canner. Do not pick at or scratch fuses while
cleaning lids. Use only canners that have the Underwriter's Laboratory (UL)
approval to ensure their safety.
Replacement gauges and other parts for canners are often available at
stores offering canning equipment or from canner manufacturers. When
ordering parts, give your canner model number and describe the parts
needed.
======================================================= === * USDA
Agriculture Information Bulletin No. 539 (rev. 1994) * Meal-Master format
courtesy of Karen Mintzias
From Gemini's MASSIVE MealMaster collection at www.synapse.com/~gemini

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