•Fill hot foods into jars and adjust headspace as specified in recipes.
•Tighten screw bands securely, but if you are especially strong, not as tightly as possible.
•Process and cool jars.
•Store the jars in a relatively cool, dark place, preferably between 50 and 70 F.
•Can no more food than you will use within a year.
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.
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.