term "processing" refers to methods of heating foods
after packing them into preserving jars. Heat processing
is key in keeping home-preserved food safe during storage.
destroys the yeast, mold, and bacteria that can infect
a jar after it's packed. Left untreated, these microorganisms
spoil the contents and can cause illness. Proper processing
creates an airtight vacuum seal between the lid and
the jar, preventing microorganisms from entering during
storage. High temperatures also destroy enzymes so fruits
and vegetables retain their color, texture, and quality.
For fruits (which are naturally acidic) and acidic vegetables
(such as most tomatoes), processing involves heating the
packed jars in a boiling-water bath. This requires a large
canning kettle filled with enough briskly boiling water
to cover the jars by one to two inches. A lid covers the
canner, while a removable rack keeps the jars from sitting
directly on the bottom, holds them relatively steady during
processing, and easier to lift from the water once processing
For foods with little natural acidity—such as corn,
beans, meat, or fish—"pressure canning" is
necessary in order to raise the boiling point above 212°
F (100° C). This generates high enough temperatures
to kill heat-resistant microorganisms and their spores.
While pressure canning is more complicated, it's absolutely
essential to keep low-acid foods safe.
There are lots of resources available! Beginning canners
and seasoned preservers alike can look for up-to-date
guides to home preserving in grocery stores, or check
out sites such as Homecanning.com.
Having current information is important!
Good luck and have fun. You'll enjoy the fruits of your
labors come winter!