*  Exported from  MasterCook  *
                     RECOMMENDED CANNERS (PART 2 OF 3)
 Recipe By     : 
 Serving Size  : 1    Preparation Time :0:00
 Categories    : Canning                          Information
   Amount  Measure       Ingredient -- Preparation Method
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   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
   ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ  ÿ * USDA Agriculture Information Bulletin No. 539
   (rev. 1994) * Meal-Master format courtesy of Karen
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