*  Exported from  MasterCook  *
 
               ENSURING HIGH-QUALITY CANNED FOODS (PART 2 OF
 
 Recipe By     : 
 Serving Size  : 1    Preparation Time :0:00
 Categories    : Canning                          Information
 
   Amount  Measure       Ingredient -- Preparation Method
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 *****  NONE  *****
 
   Advantages of Hot-packing
   
   Many fresh foods contain from 10 percent to more than
   30 percent air. How long canned food retains high
   quality depends on how much air is removed from food
   before jars are sealed.
   
   Raw-packing is the practice of filling jars tightly
   with freshly prepared, but unheated food. Such foods,
   especially fruit, will float in the jars. The
   entrapped air in and around the food may cause
   discoloration within 2 to 3 months of storage.
   Raw-packing is more suitable for vegetables processed
   in a pressure canner.
   
   Hot-packing is the practice of heating freshly
   prepared food to boiling, simmering it 2 to 5 minutes,
   and promptly filling jars loosely with the boiled food.
   
   Whether food has been hot-packed or raw-packed, the
   juice, syrup, or water to be added to the foods should
   also be heated to boiling before adding it to the
   jars. This practice helps to remove air from food
   tissues, shrinks food, helps keep the food from
   floating in the jars, increases vacuum in sealed jars,
   and improves shelf life. Preshrinking food permits
   filling more food into each jar.
   
   Hot-packing is the best way to remove air and is the
   preferred pack style for foods processed in a
   boiling-water canner At first, the color of hot-packed
   foods may appear no better than that of raw-packed
   foods, but within a short storage period, both color
   and flavor of hot-packed foods will be superior.
   Controlling Headspace
   
   The unfilled space above the food in a jar and below
   its lid is termed headspace. Directions for canning
   specify leaving 1/4-inch for jams and jellies,
   1/2-inch for fruits and tomatoes to be processed in
   boiling water and from 1- to 1-1/4-inches in low- acid
   foods to be processed in a pressure canner This space
   is needed for expansion of food as jars are processed,
   and for forming vacuums in cooled jars. The extent of
   expansion is determined by the air content in the food
   and by the processing temperature. Air expands greatly
   when heated to high temperatures; the higher the
   temperature, the greater the expansion. Foods expand
   less than air when heated.
   
   ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿ  ÿ * USDA Agriculture Information Bulletin No. 539
   (rev. 1994) * Meal-Master format courtesy of Karen
   Mintzias
  
 
 
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